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GVN Bulletin, November 2004
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From: Ed Venzke <venzke@volcano.si.edu>
Bulletin of the Global Volcanism Network
Volume 29, Number 11, November 2004
Andaman Islands (India) False reports of eruptions and confusion following
the M 9 earthquake
Ijen (Indonesia) News report cites increased activity beginning on 17 June 2004
Soputan (Indonesia) 12 December eruption covered villages with ash up to 2
cm thick
Manam (Papua New Guinea) Vigorous late-2004 eruptions cause 5 deaths and
lead to large evacuations
Erta Ale (Ethiopia) On 4-5 December 2004 visitors noted active hornitos but
solidified lava lake
Cotopaxi (Ecuador) Seismically quiet in January-April 2004; planning for
emergency water supplies
Reventador (Ecuador) Late 2004 visits find renewed venting and thick
intracaldera lava flows 2 km long
Fuego (Guatemala) Explosions and lava flows continued in November-December 2004
Dedicated to victims and survivors of the 26 December 2004 earthquake and
tsunami
As we go to press with this issue of the Bulletin our thoughts repeatedly
turn to the victims and survivors of the disastrous 26 December M 9
earthquake and tsunami. Although a different geologic process than we
discuss here, tsunamis are sometimes associated with volcanism. Conversely,
large earthquakes can trigger eruptions. The world has much to learn about
these and related geologic phenomena and about how to gauge, discuss, and
prepare for infrequent but potentially devastating events. We offer our
condolences and encouragement as we look towards a more integrated,
educated world.
Editors: Rick Wunderman, Edward Venzke, and Gari Mayberry
Volunteer Staff: Robert Andrews, Jacquelyn Gluck, William Henoch, and Aditi
Bhaskar
Andaman Islands
Indian Ocean, India
12.29°N, 93.88°E; summit elev. 305 m
All times are local (= UTC + 5 ½ hours)
False reports of volcanism surfaced describing eruptions at Barren Island
and Narcondum volcanoes (figure 1) following the 26 December 2004, M 9
earthquake off the W coast of northern Sumatra. Clarification was provided
by Dornadula Chandrasekharam of the Indian Institute of Technology. He
reported an absence of volcanic activity at these volcanoes, and at
Sumatran volcanoes, as recently as 4 January 2005.
Figure 1. A map of the Andaman Islands showing the only volcanoes known to
have erupted during the Holocene period (past 10,000 years), Narcondum and
Barren Island (N and B, respectively). Note that narrow straits break
Andaman island into multiple smaller islands (eg., Middle Andaman and
Baratang islands). Baratang Island contains an established, studied, active
mud volcano that reactivated after the M 9 earthquake.
The erroneous accounts were discovered by Chandrasekharam while watching
television news. He immediately contacted people in the Andaman region.
Upon learning that these reports were incorrect, he contacted media sources
and the Global Volcanism Network. Many Indian news sources that proclaimed
eruptions at Barren Island later withdrew their reports. The erroneous
information prevailed for a day to perhaps a week, although non-Indian news
agencies were slower to recognize and acknowledge the error.
Regional tectonic setting. Figure 2 illustrates the rudiments of the
regional tectonic setting, including the primary M 9 earthquake and
aftershocks for the next 10 days. The tectonic reconstructions are far more
complex than shown here, and the details are variously interpreted.
Figure 2. Map showing the broad tectonic setting on which Barren Island and
Narcondam volcanoes reside. The map began with the main shock of the M 9
earthquake and the earthquakes that followed during the next 11 days. USGS
preliminary tabulations computed the main shock as Mw 9.0 with a focus at
30 km depth.
In terms of local time (in the Andaman Islands and India, i.e. India
Standard Time), the epicenters shown occurred during the time interval
06:28:53 on 26 December to about 06:57 on 6 January. (In terms of UTC, this
represents the interval 00:58:53 on 25 December to about 19:57 on 5 January
2004). This digital map was extracted by applying a video simulation of
epicenters with time (Jones and others, 2002) to the recent seismic data.
The figure shows two prominent curving tectonic features crossing both
Java-Sumatra and the Andaman Sea (the Nicobar and Andaman Islands region).
One such curving feature is the volcanic front, on which lie all the active
volcanoes of Java and Sumatra, and farther N, Barren Island and Narcondam.
Outboard of that (to the W) is the second curving feature, the Sunda trench
and islands adjacent to it (the Andaman Islands, and islands to the W of
northern Sumatra hard-hit by the M 9 earthquake and tsunami). The trench
reflects the sea-floor expression of the subduction zone, and represents
the region where the M 9 earthquake occurred. The offset, often termed a
'megathrust,' involved 1,200 km of rupture along the subduction zone, and
suddenly shifted the Indian Ocean's floor ~15 m towards Sumatra (Hopkin, 2005).
Regarding the M 9 earthquake, according to the USGS, the local time and
date in terms of local time in N Sumatra at the epicenter was Sunday, 26
December 2004 at 07:58:53 (i.e., roughly 8 am). The USGS provided a table
showing the time of the main shock in a variety of time zones.
Some excellent tutorials have provided background on the tectonic setting,
the earthquake, and the tsunami. These have appeared in the press and on
the web (eg. Sieh, 2004, 2005; NOAA, www.noaa.gov/tsunamis.html).
Although large earthquakes may trigger volcanism (Linde and Sacks, 1998),
so far this does not appear to be the case, at least at the volcanoes of
Barren Island and Narcondum.
Mud volcanoes and ensuing confusion. Post-earthquake reports of active 'mud
volcanoes' in the Andaman Islands caused panic and confusion in the region,
and came at a particularly bad time. Chandrasekharam pointed out that in
Andaman, like many other arc provinces, several mud volcanoes are present.
These are not real volcanoes in the usual sense, but because they may build
a small, low-profile cone of local extent around the hole through which the
mud is thrown out, they are known as mud volcanoes (figure 3).
Figure 3. A 2003 photograph showing about a quarter to one half of a mud
volcano on Baratang island (top) and its largest crater (~ 20 cm in
diameter, ~ 28 cm in depth) (bottom). This site was known as a minor
fissure prior to 1983; but in that year the largest outburst occurred,
chiefly emitting warm (~ 30°C) mud. Mud again began emerging in February
2003. The dominant feature was a sub-circular mound of mud, ~ 30 m in
diameter with a height of ~ 2 m at the center. Observers noted a colorless,
sulfurous smelling gas. The mud contained angular to sub-rounded rock
fragments from underlying strata. No photos nor similarly detailed
technical reports have been received showing alleged recent activity that
began 27 December 2004 (see text for news report). All photos and data
courtesy of the Geological Survey of India, Eastern Region.
Some of the difficulty with the news reports was that the mud volcanoes'
locations, numbers, and impacts remained vague, and that Barren Island
became intertwined with story. An extreme example came from an
irresponsible report in the tabloid India Daily (2 January 2005), which
contained the title "Volcano[es] Barren-1 and Narcondam erupt in
Andaman--Seismic disturbance can cause more tsunami." It continued with
wild claims such as, "Severe seismic activities are seen in these islands .
. . personnel who have reached these remote areas are facing shattering
earth vibrations and high waves," and "Some scientists are predicting
severe earthquake again in the North of Andaman Nicobar Islands. The effect
can be severe on Myanmar, Andaman, Indi[a]'s east coast, Bangladesh and
Sumatra . . .." They added, "Andaman's tribals strangely are unaffected as
most of them somehow went [to] higher ground before the tsunami. So did the
animals." Science journalism clearly has a lot to compete with (see
Oldenburg, 2005, for more discussion of these topics).
One alleged mud volcano 'Barren-1' has a name so close to the volcano's
name (Barren Island) that it was frequently confused. The mud volcano's
name (if there is one) appears to be absent from the technical literature
at the Geological Survey of India's website.
On a positive note, one mud volcano received consistent mention in a number
of news articles and provided coverage generally congruent with geological
data posted by the Geological Survey of India. According to an article in
India News (with the leader, "Port Blair, 30 December"), "A mud volcano at
the inhabited Baratang Island in Middle Andaman has erupted but the
administration said there was no cause for concern. 'Mud keeps bubbling in
the volcano, but on December 28, the eruption was up to three meters and
there was considerable heat,' Inspector General of Police S. B. Deol said
here."
"He [also] said the mud volcano was located on one side of the Baratang
Island, which was about 100 km from Port Blair. People live on the other
side, but there is no cause for concern."
A report in the India Daily was nearly identical. Details on a Geological
Survey of India website noted that the Baratang mud volcano began erupting
on 27 December 2003 (figure 3 and caption). Mud volcanoes may have also
occurred elsewhere in the region, but the available news reports
consistently failed to disclose locations.
Often associated with active faults and with petroleum fields, mud
volcanoes on land consist of low-lying surface mud extrusions that vary in
size from meters to several kilometers across. They emit mud at
temperatures significantly below magmatic, which are typically at least
800°C. Eruptions from mud volcanoes can reach heights of several hundred
meters and consist of mud, fluids and gases, and sometimes burning
hydrocarbons. Although in submarine environments mud volcanoes can be
extensive, deadly mud volcano eruptions are extremely rare because their
eruptions seldom move far enough to affect large areas of the land
surface. Their greatest danger may be to curious onlookers who venture too
close.
References. Jones, A., Siebert, L., Kimberly, P., and Luhr, J.F., 2002,
Earthquakes and Eruptions, v. 2.0 (CD-ROM): Smithsonian Institution, Global
Volcanism Program, Digital Information Series, GVP-2.
Hopkin, M., 2005, Triple slip of tectonic plates caused seafloor surge:
Nature, v. 433, no. 3 (06 Jan 2005).
Linde, A.T., and Sacks, I.S., 1998, Triggering of volcanic eruptions:
Nature, v. 395, p. 888-890.
Oldenburg, D., 2005, A sense of doom: Animal instinct for
disaster--Scientists investigate wildlife's possible warning systems: The
Washington Post (8 January 2005), p. C1, C3 (URL:
www.washingtonpost.com/).
Sieh, K., 2004, The science behind the Aceh earthquake: Caltech Media
Relations (30 December 2004), (URL:
pr.caltech.edu/media/Pres...2628.html).
Sieh, K., 2005, In Sumatra: Notes From a Geologist in the Field: Caltech
Today (1 January 2005; URL: today.caltech.edu/today/).
U.S. National Earthquake Information Center (NEIC) (URL:
earthquake.usgs.gov)./
U.S. National Oceanic and Atmospheric Administration (NOAA) (URL:
www.noaa.gov/tsunamis.html).
Background. Barren Island, a possession of India in the Andaman Sea about
135 km NE of Port Blair in the Andaman Islands, is the only historically
active volcano along the N-S-trending volcanic arc extending between
Sumatra and Burma (Myanmar). The 354-m-high island is the emergent summit
of a volcano that rises from a depth of about 2,250 m. The small,
uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with
walls 250-350 m high. The caldera, which is open to the sea on the W, was
created during a major explosive eruption in the late Pleistocene that
produced pyroclastic-flow and -surge deposits. The morphology of a fresh
pyroclastic cone that was constructed in the center of the caldera has
varied during the course of historical eruptions. Lava flows fill much of
the caldera floor and have reached the sea along the western coast during
eruptions in the 19th century and more recently in 1991 and 1995.
Narcondum volcano, an island possession of India in the Andaman Sea, is
part of a volcanic arc that continues northward from Sumatra to Burma
(Myanmar). The small 3 x 4 km wide conical island, located about 130 km
east of North Andaman Island, rises to 710 m, but its base lies an
additional 1,000 m beneath the sea. The island is densely vegetated,
bounded by cliffs on the southern side, and capped by three peaks. No
evidence of historical volcanism is present, although the summit region is
less densely vegetated and volcanism at the andesitic volcano is considered
to have continued into the Holocene. The island's name means "pit of hell,"
although the name could have been mistakenly transferred from the
historically active Barren Island volcano, 140 km to the SSW.
Information Contacts: Dornadula Chandrasekharam, Department of Earth
Sciences, Indian Institute of Technology, Bombay 400076, India (URL:
www.geos.iitb. ac.in/dchandra/biexp/, Email: dchandra@iitb.ac.in);
India News (URL: news.newkerala.com/india-news/); India Daily (URL:
www.indiadaily.com/); The Washington Post, Washington DC, USA (URL:
www.washingtonpost.com/); Geological Survey of India, 27 Jawaharlal
Nehru road, Kolkata (Calcutta) 700016, India.
Ijen
eastern Java, Indonesia
8.058°S, 114.242°E; summit elev. 2,386 m
All times are local (= UTC + 7 hours)
The Chief of the local National Park has been quoted as having reported an
increase in activity beginning on 17 June 2004. This resulted in closing
the area to visitors. Reuters quotes him as having said "There have been
sulfuric rocks coming out of the edge of the crater and the fluid in it
(the crater lake) has turned from green to white and has emitted hot foam.
There are also increasing tremors."
Background. The Ijen volcano complex at the eastern end of Java consists of
a group of small stratovolcanoes constructed within the large 20-km-wide
Ijen (Kendeng) caldera. The N caldera wall forms a prominent arcuate ridge,
but elsewhere the caldera rim is buried by post-caldera volcanoes,
including Gunung Merapi stratovolcano, which forms the 2,799-m-high point
of the Ijen complex. Immediately W of Gunung Merapi is the renowned
historically active Kawah Ijen volcano, which contains a nearly 1-km-wide,
turquoise-colored, acid crater lake. Picturesque Kawah Ijen is the world's
largest highly acidic lake and is the site of a labor-intensive sulfur
mining operation in which sulfur-laden baskets are hand-carried from the
crater floor. Many other post-caldera cones and craters are located within
the caldera or along its rim. The largest concentration of post-caldera
cones forms an E- to W-trending zone across the southern side of the
caldera. Coffee plantations cover much of the Ijen caldera floor, and
tourists are drawn to its waterfalls, hot springs, and dramatic volcanic
scenery.
Information Contact: Reuters News Service.
Soputan
Sulawesi, Indonesia
1.11°N, 124.73°E; summit elev. 1,784 m
All times are local (= UTC + 8 hours)
Soputan erupted again on 12 December 2004. The Directorate of Volcanology
and Geological Hazard Mitigation (DVGHM) noted that an eruption on 18
October 2004 sent a cloud ~600 meters above the crater. The previous
eruptive episode occurred during July and August 2003 (Bulletin v. 28, nos.
8, 10, and 11). A summary of ash plumes from mid-2003 through 12 December
2004 appears in table 1. Large discrepancies appeared in reported ash
column heights; with the satellite estimates about 10 times larger than
ground-based estimates.
Table 1. Reported ash plume altitudes recorded from Soputan, 18 July
2003-12 December 2004. Courtesy of DVGHM and Darwin VAAC.
Date Height (km) (comment) Source
18 Jul 2003 ~ 2 km above summit DVGHM
02 Sep 2003 ~ 2 km altitude Darwin VAAC
04 Sep 2003 ~ 3 km altitude Satellite imagery, Darwin VAAC
(extending ~ 75 km N
of the summit)
18 Oct 2004 ~ 600 m above summit DVGHM
12 Dec 2004 ~ 1 km above summit DVGHM
12 Dec 2004 ~ 10.7 km altitude Darwin VAAC
The earliest details mentioned by DVGHM regarding the 2004 activity
discussed 11 December 2004, a time when the tremor tended to rise,
attaining peak-to-peak amplitudes of 0.5-3.0 mm. Observers also saw
incandescence at the crater's rim.
At 0046 on 12 December tremor again registered with maximum peak-to-peak
amplitudes of ~45 mm. At 0050 on 12 December Soputan erupted, sending an
ash cloud up to 1 km. This was followed by discharge of a "hot cloud"
(pyroclastic flow ?) to a distance of ~200 m E (from 'Aeseput,' a prominent
NE-flank vent that formed in 1906). A lava flow spread W and S of Soputan.
Observers could hear rumbling noise and thunder from their monitoring
station ~11 km from the crater.
White-to-gray ash went E. At 0130 on 12 December a problem arose with the
seismic sensors, perhaps because the solar panel was covered with ash. By
0600 the sensor was down. At 0500 that day a hot cloud occurred with a run
out distance of ~150 m and a height of 200 m. Activity persisted until
1030. Soputan's summit then became visually obscured by clouds, but
observers could still make out a white thin-to-medium plume to 70-80 m
above the crater, and incandescence.
On the 13 December at 1752 observers felt an earthquake with a magnitude of
MM I-II. The seismograph was then still inoperable.
News reports. A 13 December news report in The Daily Reform Voice stated
that hundreds of hectares of paddy-fields and other agricultural land to
the W of the Soputan was seriously impacted by tephra.
Thomas Dobat, a German expatriat living in Indonesia and concerned about
the situation, sent Bulletin editors a translation of a 13 December 2004
article on Soputan taken from the Indonesian Journal Komentar. Similar to
the above report, it also noted that hundreds of villages in 13 districts
in Central Minahasa and in South Minahasa suffered from tephra fall emitted
on 11-12 December. These eruptions of Soputan were accompanied by heavy
thunder and lightning, which were heard in the town of Amurang.
Ash fell in nearly all of Central Minahasa and in parts of South Minahasa.
The result was that in all areas of Central Minahasa, especially in the
town of Tondano, houses, rice-fields, and roads were ash-covered up to 2 cm
thick.
Background. The small Soputan stratovolcano on the southern rim of the
Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of
Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano
rises to 1784 m and is located SW of Sempu volcano. It was constructed at
the southern end of a SSW-NNE trending line of vents. During historical
time the locus of eruptions has included both the summit crater and
Aeseput, a prominent NE-flank vent that formed in 1906 and was the source
of intermittent major lava flows until 1924.
Information Contacts: Directorate of Volcanology and Geological Hazard
Mitigation, Jalan Diponegoro 57, Bandung 40122, Indonesia (Email:
dali@vsi.dpe.go.id; URL: www.vsi.esdm.go.id/); Darwin Volcanic Ash
Advisory Centre, Australian Bureau of Meteorology (URL:
www.bom.gov.au/info/vaac); The Daily Reform Voice; Komentar; Thomas
Dobat, Lorong Jerman, Kauditan II, 95372, Sulawesi Utara, Indonesia.
Manam
Papua New Guinea, Northeast of New Guinea
4.10°S, 145.061°E; summit elev. 1,807 m
All times are local (= UTC - 10 hours)
Several periods of eruption took place on the island of Manam during the
last months of 2004. Rabaul Volcano Observatory (RVO) noted outbursts
during 24-31 October (Bulletin v. 29, no. 10), 10-12 November, and on 6
December. Several other plumes were noted as well. Satellite-based alerts
(MODVOLC) were noteworthy during this interval, having been absent for over
9 months.
On 6 December, the newspaper The National reported that these eruptions had
killed five people, whose deaths were primarily related to respiratory
complications from inhaling volcanic material. Volcanic ash damaged crops,
water supplies, and houses. News accounts discussed evacuations, with the
possibility of evacuating all or most of the island (figure 4). The news
also mentioned food shortages after the 24 October eruption.
Figure 4. Geography of the area around Manam showing two named villages on
the island and numerous settlements on the main island of New Guinea. For
scale, Manam Island is ~ 10 km in diameter. The volcano is sometimes
referred to as Mount Iabu in the regional press. The city of Wewak lies off
the map, ~ 160 km W of Manam; the city of Madang lies ~ 150 km to the E.
The large meandering river at left is the Sepik. The island's residents, a
total of 9,467 people, rely on subsistence farming and fishing for food,
and copra and cocoa as a source of income. Map courtesy of Jorgen Aabech.
The government of Papua New Guinea presented a new website, The National
Disaster Center, which broadly disseminates government disaster information
including volcano reports and updates (see URL under Information Contacts,
below). The website contained a Manam hazards map. Other documents on that
site noted shifting winds and the lack of a clearly safe area on the island
during the late 2004 crisis. It said that the government would sponsor
large-scale evacuations beginning on 27 November 2004.
The eruptive episode that began on 24 October continued at least a week
(figure 5). By 31 October, the eruption at Main Crater consisted of
Strombolian activity, with ash and scoria emissions. Tephra of ~1 cm
diameter were deposited in Warisi village on the SE side of the island.
Small pyroclastic flows were generated, and fresh lava flowed into the NE
radial valley. The lava flow followed the Boakure side of the valley,
covering older flows from the 1992-1994 eruption. Beginning on the morning
of the 31st, the amount of continuous volcanic tremor increased to
moderate-to-high levels, so the Alert Level was increased from Stage 1 to
Stage 2. Villagers were advised to remain away from Manam's four main
radial valleys.
Figure 5. Image of Manam and vicinity acquired on 24 October 2004 by the
Moderate Resolution Imaging Spectroradiometer (MODIS), an instrument on the
Terra satellite of the National Aeronautics and Space Administration
(NASA). Dark ash rising from Manam drifted NW along and then away from the
N coast of the main island, New Guinea. Courtesy NASA Earth Observatory.
The Darwin Volcanic Ash Advisory Center reported the 24 October outburst
(Bulletin v. 29, no. 11). On 31 October during 0813-1449 they noted a plume
at ~13.7 km altitude drifting SE on visible satellite imagery. The Aviation
Color Code was at Red, the highest level.
According to a news report, ". . . [~0.3 m] of ash with hot pumice" landed
on the roofs of houses, and ash drifted as far W as Wewak, ~100 km away.
Reportedly, ~4,000 villagers moved to safer areas.
On 2 November around 2325 a possible eruption may have produced a plume to
~7.6 km altitude, which drifted SE. Ash was visible on satellite imagery on
8 and 9 November at an altitude of ~3 km; on 9 November the plume extended,
~55 km to the NE.
A Strombolian eruption occurred during 10-11 November 2004. The ash column
from the eruption was estimated to have risen ~5-6 km above the crater, and
perhaps rose as high as ~9 km above the crater, according to an Air Niugini
pilot. The activity was accompanied by continuous weak to moderate roaring
and rumbling noises and frequent loud explosions. Light ash and scoria fall
was reported near local villages. As of 2130 on 10 November ash reached 7
km altitude and 147 km to the SW. As of 12 November, the ash emissions
reached 10 km altitude and extended laterally 74 km W to NW of the volcano.
During this reporting interval Darwin VAAC noted that a SE-drifting plume
was visible on satellite imagery on 31 October during 0813-1449 at an
altitude of ~13.7 km.
A satellite image from the Terra Moderate Resolution Imaging
Spectroradiometer (MODIS) on 15 November shows a large brown ash plume
blowing SW (figure 6).
Figure 6. Manam image acquired 15 November 2004 from Moderate Resolution
Imaging Spectroradiometer (MODIS) passing overhead on the National Aviation
and Space Agency (NASA) Terra satellite. Dark ash rises from Manam and
drifts SW over New Guinea. Courtesy NASA Earth Observatory.
According to RVO scientists, on 23-24 November Main Crater ejected glowing
lava and discharged an ash cloud that rose ~10 km high. A lava flow was
also reported to be heading for two villages on the island. At 1850 on 23
November, a phase of strong Strombolian eruption began producing a
continuous, thick ash column that rose about 10 km above the summit. The
ash cloud emissions were accompanied by projection of glowing lava
fragments, loud roaring and rumbling noises, and occasional loud and
banging noises that produced shock waves. A continuous bright red glow
visible down the NE valley indicated emplacement of a lava flow.
The lava flow was reported heading NE towards villages of Kolang and Bokure
1. In addition to the lava, Manam emitted large rocks. Around this time the
aviation red alert issued for aircraft noted that the ash plume extended
130 km SE of Manam.
Press accounts stated that emergency officials said an area was being
cleared on the mainland for a possible full-scale evacuation of Manam's
~9,500 islanders. Evacuation was to become compulsory if activity
intensified from Stage 3 (which was set by 22 November) to Stage 4. Some 20
bush homes had collapsed due to 'mud rain' (presumably, falling tephra),
and five people had been injured.
RVO reported that a slight increase in eruptive activity from Main Crater
began after 1600 on 26 November, which continued until 0800 on the 29th.
Summit activity consisted of continuous forceful emission of thick dark
gray ash clouds that rose less than 1 km above the summit before being
blown NW. Fine ashfall to the NW at Zogari and Iassa villages was reported
from about 1700. A single weak roar was heard between 0600 and 0700 on the
27th.
Seismicity was moderate to moderate-high at 2300 on the 26th and 0800 on
the 27th. Volcanic tremors continued to be recorded suggesting the system
remained dynamic and capable of ongoing variable eruptions, with sporadic
more vigorous phases.
On 28-29 November, RVO reported that ash clouds were rising less than 1 km
above the summit before being blown by the shifting NNE and NNW winds. Fine
ashfall was reported at Warisi. Weak roaring noises were heard between
1900-2400 on the 28th. A weak glow with weak projections of incandescent
lava fragments was visible during the night of the 28th, and Southern
Crater released thin white vapor only.
Some press reports described 7,900 persons evacuated from Manam. According
to the Planet Diary web site, about 9,000 people were evacuated by 1
December 2004 as the eruption grew more violent.
Mid-afternoon on 5 December RVO noted a slight change in activity at
Southern Crater marked by commencement of sub-continuous weak to moderate
roaring and rumbling noises. The noises continued until 1000 that day. As
darkness fell, intervals of visibility occurred (eg., during 1800-1808,
2030-2108, and 2130-2200); observers saw sub-continuous lava fountaining.
Meanwhile, from Main Crater there came a series of sub-continuous,
forceful, moderately thick, gray-brown ash-laden clouds, which were
occasionally visible above the weather clouds. The ash plume rose between
about 600 and 900 m above the summit and drifted to the E and NE. Light
ashfall and fine scoria fell at the villages Abaria and Bokure 1.
Fluctuating audible noises consisted of low roars, 'jet engine' roars, and
occasional still-louder roars. Although visibility was generally poor due
to volcanic ash clouds from both craters, observers could still make out
variable glow coming from the craters.
On 8 December 2004, The National reported that, according to RVO, Manam
erupted starting on the morning of 6 December. Fist-sized scoria were
thrown out of the vent into the air, hitting houses in the villages below.
The eruption began at 0800 and peaked at 1150 with "seismicity continuing."
The National also reported that a pyroclastic flow occurred in the SE
valley during the 6 December eruption, with ash and cloud directed NW. On
the 6th, residents of Madang (~150 km E of Manam) described feeling tremor
or ground motion; those in Wewak (~160 km to the W) reported similar
sensations and also noted volcanically derived dust. Although ash from 6
December was apparently widespread, Googling for news of Manam ash in Irian
Jaya failed to turn up any reports from there.
The Darwin VAAC reported ash plume sightings from satellites during 12-14
December, and the RVO reported moderate eruptions continuing in that period.
Fatalities. An article by Bonney Bonsella in The National showed pictures
of Manam Islanders in evacuation. They waded through shallow surf to board
through the open bow of a large beached landing craft. The article
discussed fatalities during the eruption.
"The volcanic eruption on Manam Island in the Madang province has so far
claimed five lives-two elderly women and three children between the ages of
5-13. The coordinator of the Manam evacuation exercise Camillus Dugumi
confirmed the deaths, adding that the deaths were linked to respiratory
complications resulting from inhaling volcanic ashes and dust. Mr Dugumi,
who is also the district health programme manager, said one of the deaths
was that of an elderly women from Bokure village recorded early last week
at the Bogia District hospital. The women died after being admitted to the
hospital for respiratory complications. One child, a little boy, died on
Friday at the Asuramba care centre after suffering pneumonia."
"Three others-an adult women and two other children-had died during earlier
volcanic activity on Manam."
Displaced residents. The above-mentioned article related that three
State-owned plantations (called Asuramba, Potsdam, and Magem (and Daigul?))
were set aside, ". . . at least for the time being[,] to accommodate a
speedy resettlement of the displaced Manam islanders." Another news article
noted that these plantations are near the town of Bogia (figure 4). The
National Disaster Center website noted that "The three plantations were
bought off from the lessee in 1995 for K1.25 million following a National
Executive Council decision for the purpose of resettlement of Manam
Islanders displaced by volcanic activity." Controversies remain with
respect to land issues. Still , that website noted that the long-term
solution advocated by the President, Manam Local Level Government is to
resettle the people of Manam on the mainland. For this purpose the
Provincial Disaster Committee has identified State land to resettle the
Manam Island people.
MODVOLC. The MODIS infrared instrument flown on the NASA Terra and Aqua
satellites showed an impressive set of thermal alerts beginning 21 October
2004 (figure 7). Since the beginning of MODVOLC operations (Bulletin v. 28,
no. 1) thermal alerts occurred at Manam during only two periods. The first,
7 April-21 May 2002, was related to increased Strombolian activity
(Bulletin v. 27, no. 5). The second period, 21 October until at least 14
December 2004, was associated with the current crisis and was a time when
alert ratios and summed radiances reached higher values than during the
first period. These parameters are consistent with a highly active vent
and/or lava flows, and in accord with vigorous Strombolian emissions seen
in the field.
Figure 7. MODVOLC thermal alert ratios, number of alert pixels, and summed
4 mm radiance plots for Manam from 1 January 2001 until 31 December 2004.
Alerts occurred only between 7 April and 21 May 2002 and between 21 October
and 14 December 2004. Thermal alerts collated by Charlotte Saunders, and
David Rothery; data courtesy of the Hawaii Institute of Geophysics and
Planetology's MODIS thermal alert team.
This analysis of MODIS thermal alerts (using the MODVOLC alert-detection
algorithm) is based on data extracted from the MODIS Thermal Alerts website
maintained by the University of Hawaii HIGP MODIS Thermal Alerts team.
Thermal alerts are based on an 'alert ratio,' and an alert is triggered
whenever this ratio has a value more positive than -0.8. This threshold
value was chosen empirically by inspection of images containing known
volcanic sites at high temperature, and is the most negative value that
avoids numerous false alarms. There are also some day-time alerts, which
are based on the same algorithm but incorporating a correction for
estimated solar reflection and a more stringent threshold whereby the alert
ratio is required to be more positive than -0.6 in order to trigger an alert.
Background. The 10-km-wide island of Manam, lying 13 km off the northern
coast of the mainland Papua New Guinea, is one of the country's most active
volcanoes. Four large radial valleys extend from the unvegetated summit of
the conical 1,807-m-high basaltic-andesitic stratovolcano to its lower
flanks. These "avalanche valleys," regularly spaced 90 degrees apart,
channel lava flows and pyroclastic avalanches that have sometimes reached
the coast. Five small satellitic centers are located near the island's
shoreline on the northern, southern and western sides. Two summit craters
are present; both are active, although most historical eruptions have
originated from the southern crater, concentrating eruptive products during
the past century into the SE avalanche valley. Frequent historical
eruptions have been recorded at Manam since 1616. A major eruption in 1919
produced pyroclastic flows that reached the coast, and in 1957-58
pyroclastic flows descended all four radial valleys. Lava flows reached the
sea in 1946-47 and 1958.
Information Contacts: Rabaul Volcano Observatory (RVO), P.O. Box 386,
Rabaul, Papua New Guinea; National Disaster Centre, Department of
Provincial Affairs and Local Level Government (Ministry of Inter-Government
Relations), PO Box 4970, Boroko, National Capital District, Papua New
Guinea (URL: www.pngndc.gov.pg/); David Innes, Flight Safety Office,
Air Niugini (Email: dinnes@airniugini.com.pg or deejayinnes@yahoo.com);
Andrew Tupper, Darwin Volcanic Ash Advisory Centre, Australian Bureau of
Meteorology (URL: www.bom.gov.au/info/vaac); Jorgen Aabech,
Skogbrynet 40B, N-1709 Sarpsborg, Norway (Email: Jorgen.aabech@eunet.no;
URL: http:// www.vulkaner.no); MODIS Thermal Alert System, Hawaii Institute
of Geophysics and Planetology (HIGP), School of Ocean and Earth Science and
Technology, University of Hawaii at Manoa (URL:
www.modis.higp.hawaii.edu); David Rothery and Charlotte Saunders,
Department of Earth Sciences, The Open University, Milton Keynes, MK7 6AA,
United Kingdom (Email: d.a.rothery@open.ac.uk); Kevin Pamba and Bonney
Bonsella, The National (URL: www.thenational.com.pg/1206/).
Erta Ale
Ethiopia
13.60°N, 40.67°E; summit elev. 613 m
Two teams sent reports on Erta Ale's behavior in December 2004. On 1-5
December the visiting team included Jacques-Marie Bardintzeff and a group
from Ushuaia Nature, and on 4-5 December the team consisted of the
volcanology travel group SVE-SVG. Both groups submitted similar reports and
commented on substantial changes they observed compared to conditions
described in past reports (most recently, Bulletin v. 29, no. 8). Although
Erta Ale frequently contains a lava lake with an open surface of molten
lava, that was not the case this time.
The lava lake's surface had chilled within the small (~200-m-diameter) S
pit crater (figure 8). A solidified lava crust covered the crater floor.
The crust's surface sat ~15 m below the W crater rim, and ~30 m below the E
crater rim. On top of this crust stood four coalesced hornitos in the SE
part of the S crater (figure 9). They were ~10 m high and represented the
only portion of the crust where molten material was in evidence. Two
hornitos emitted high temperature (more than 500°C) SO2-rich gas. Another
hornito contained glowing molten lava. During the night of 4 December the
SVE-SVG group saw degassing and incandescent lava at the summit of two of
these hornitos. Bardintzeff described sampling molten material from 12 m
depth, in one of the hornitos using a cable and an iron mass (figure 9).
Figure 8. The small S pit crater at Erta Ale as viewed from the E on 5
December 2004. Hornitos had grown on the W part of the crater floor; except
for these windows into the molten material at depth, the rest of the lava
lake surface had completely solidified. Photo provided by J. M. Bardintzeff.
Figure 9. The S pit crater at Erta Ale as seen from the W on 5 December
2004, with the 4 hornitos in the center of the photo. Two hornitos on the
left emitted high temperature SO2. The hornito in the right foreground
contained molten lava (which was sampled). Photo provided by J. M. Bardintzeff.
The SVE-SVG team noted recent activity within the North crater, where an
uplifted area termed a 'lava bulge' had solidified. It covered ~80% of the
crater floor and rose to about 20-25 m below the crater rim. In the lava
bulge's central area, strong and noisy degassing of SO2 spouted from
several small hornitos. At the bulge's periphery the observers saw ten
small incandescent vents. Subsequently, two plumes rose above the volcano.
Background. Erta Ale is an isolated basaltic shield volcano that is the
most active volcano in Ethiopia. The broad, 50-km-wide volcano rises more
than 600 m from below sea level in the barren Danakil depression. Erta Ale
is the namesake and most prominent feature of the Erta Ale range. The
613-m-high volcano contains a 0.7 x 1.6 km, elliptical summit crater
housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide
depression elongated parallel to the trend of the Erta Ale range is located
to the SE of the summit and is bounded by curvilinear fault scarps on the
SE side. Fresh-looking basaltic lava flows from these fissures have poured
into the caldera and locally overflowed its rim. The summit caldera is
renowned for one, or sometimes two long-term lava lakes that have been
active since at least 1967, or possibly since 1906. Recent fissure
eruptions have occurred on the northern flank of Erta Ale.
Information Contacts: Jacques-Marie Bardintzeff, Laboratoire de
Petrographie-Volcanologie, Bât. 504, Universite Paris-Sud, F-91405, Orsay,
France (Email: bardizef@geol.u-psud.fr, URL:
www.lave-volcans.com/bardintzeff.html); Henry Gaudru, Societe
Volcanologique Europeenne (SVE), C.P.1-1211 Geneva 17- Switzerland (Email:
HgaudruSVE@compuserve.com; URL: www.sveurop.org/).
Cotopaxi
Ecuador
0.677°S, 78.436°W; summit elev. 5,911 m
All times are local (= UTC - 5 hours)
Seismicity at Cotopaxi during December 2003 through December 2004 yielded
averages that generally remained within normal levels (table 2). Steam
emissions continued, and sulfurous odors were occasionally reported. A plot
of total seismicity each week during 2001-July 2004 portrayed numerous
peaks and valleys in the range 50-200 events per week. Occasional
excursions took the weekly totals to several hundred events in late 2001
and early 2002 (peaking at over 700 events per week during mid-October
2001). The 2004 data lacked such dramatic excursions.
Table 2. Annual summaries showing typical daily averages of various kinds
of seismicity at Cotopaxi during 2001-2004. Courtesy of IG (shown on their
website in the January 2005 report).
Year Volcano-tectonic Hybrid Long-period Tornillo
Tremor Total
2001 3.1 1.0 10.2 0.1 0.2
11.3
2002 2.9 3.0 14.6 0.1 0.4
18.2
2003 1.2 3.7 9.3 0.0 1.4
14.2
2004 0.41 3.59 11.10 0.0 1.56
15.11
Planning for emergency water supplies. Although seismicity and other
monitored parameters were moderate to low during most of 2003 (Bulletin v.
28, nos.11 and 12), local authorities worked on a contingency plan for
emergency drinking water in the event of a crisis at Cotopaxi.
The Quito metropolitan sanitation and drinking water company (EMAAP-Q)
prepared a contingency plan for residents around Cotopaxi. The challenge
was to provide for sufficient amounts of potable and sanitation water for
some half a million people in the event of an eruption that contaminates
their normal water supplies. This contingency plan was drawn up using
experience gained from the operational emergency plan used to recover from
the eruption in 1998-99 and the Reventador eruption in 2002.
During the Guagua Pichincha eruption, pyroclastic material impacted Quito,
and ash fell into the water treatment plants and threatened the water
supply systems. EMAAP-Q developed an operational and emergency plan. The
plan was tested in 1999 when the volcano had two major eruptions that heat
dropped ash on Quito and its infrastructure.
Background. Symmetrical, glacier-clad Cotopaxi stratovolcano is Ecuador's
most well-known volcano and one of its most active. The steep-sided cone is
capped by nested summit craters, the largest of which is about 550 x 800 m
in diameter. Deep valleys scoured by lahars radiate from the summit of the
andesitic volcano, and large andesitic lava flows extend as far as the base
of Cotopaxi. The modern conical volcano has been constructed since a major
edifice collapse sometime prior to about 5,000 years ago. Pyroclastic flows
(often confused in historical accounts with lava flows) have accompanied
many explosive eruptions of Cotopaxi, and lahars have frequently devastated
adjacent valleys. The most violent historical eruptions took place in 1744,
1768, and 1877. Pyroclastic flows descended all sides of the volcano in
1877, and lahars traveled more than 100 km into the Pacific Ocean and
western Amazon basin. The last significant eruption of Cotopaxi took place
in 1904.
Information Contact: Geophysical Institute (IG), Escuela Politecnica
Nacional, Apartado 17-01-2759, Quito, Ecuador (URL: www.igepn.edu.ec/).
Reventador
Ecuador
0.078°S, 77.656°W, summit elev. 3,562 m
All times are local (= UTC - 5 hours)
A 16 December 2004 report from the Instituto Geofisico (IG) of the Escuela
Politecnica Nacional calls attention to renewed lava effusion from the
crater that lies within Reventador's large summit cone (figure 10). A
block-lava flow escaped the cone's crater. It ran out at a breach in the S
wall, and by 16 December it had advanced ~2 km farther. The flow advanced
SE along a narrow, E-curving path, remaining atop lavas from 2002. Thus far
in 2004, lava flows remained well within the larger caldera.
Figure 10. An aerial photo of Reventador's 4-km-diameter caldera as a base
for mapping the lava flows of 2002 and those of 2004 through mid-December.
The 2002 flows are labeled Lava 1 and Lava 2. The 2004 lava flow followed
and partly covered Lava 1. At a distance of ~ 1 km from the vent, the 2004
lava flow bifurcated into two closely spaced parallel lobes. The caldera
has an E-tilting floor, is open on its E side, and contains a prominent
cone on its W side. The cone forms the volcano's summit, and contains an
elongate crater that hosts the 2004 vent ("active vent"). The crater has a
rim that is indicated by a solid curving line; the crater's inward-sloping
walls are indicated by light shading and lines resembling the trends of
gullies. The cone's floor at its southern breach lies at ~ 3,200 m
elevation. The aerial photo was taken by Instituto Geografico Militar in
1983. Figure courtesy of IG.
Reports in 2003 chiefly discussed events outside the caldera. A road, one
gas pipeline, and two oil pipelines traverse Reventador's flanks 7 km ESE
of the active vent. All of these installations were affected in 2003 (but
not appreciably since then). The pipelines were destroyed due to heavy
lahars coming down the Reventador river on 6 May 2003 (Bulletin v. 28, no.
6). Our last report (Bulletin v. 28, no. 11) discussed events during July
through most of November 2003.
Lava venting in the crater likely began in early November 2004, a time when
seismic station CONE registered dramatic increases in volcano-tectonic
events (figure 11). In response to the elevated seismicity, the IG-EPN
began more intensive monitoring, including overflights with thermal
imaging, repeat visits to the remote volcano, and on 9 November 2004,
installation of the additional short-period seismic station LAV3, ~2 km
from the crater's vent.
Figure 11. Seismicity (number of earthquakes) versus time registered at
Reventador (station CONE) during mid-February 2003 through mid-December
2004. Anomalously elevated seismicity consisting mainly of volcano-tectonic
began in August 2004. Activity increased on 4 November 2004 and included
hybrid events. Previously unseen emergent, extended-duration, broad-band
earthquakes began on 22 November 2004. Courtesy of IG.
A helicopter overflight by IG-EPN staff on 10 November 2004 confirmed the
presence of a small lava dome, which appeared then to be confined to the
crater floor. This feature was not present on photos taken during an IG
overflight on 19 October 2004. During the 10 November overflight, a
continuous 2.5 km-high gas column escaped from the crater, accompanied by
sulfurous odors detected by personnel in the helicopter.
The date when lava began escaping the crater was not precisely known, but
it was thought to have been around 22 November, coincident with the
emergence of distinct seismic signals not previously observed at Reventador
(figure 11). The signals occurred in swarms and consisted of low-frequency
(1-10 Hz) waves of relatively low-amplitude. Their seismic records were
emergent (i.e. growing in amplitude with time) and of long duration (up to
60 seconds). They are thought to have been possibly associated with rock
falls from lava flowing down the cone's southern flank. As many as 200 of
these events were recorded each day at station CONE.
A return visit to the crater rim on 28 November (this time on foot)
documented abundant fresh lava in the crater (figure 12), a dramatic
increase in the volume of lava there. At least 0.5 x 10^6 m^3 of new lava
then covered the entire crater floor and appeared to be already flowing out
of the southern breach and into the surrounding caldera. Because of cloudy
weather, the exact extent of the flow remained indeterminate. The surface
of this lava flow also extended to the N and reached a level ~20 m below
the northern breach. Continuous lava extrusion or flowing or both were
heard within the crater, making sounds akin to glass breaking, and vigorous
roaring gas emissions originated from the crater's western margin. These
gas emissions and other smaller fumaroles contributed to a plume that was
continuously present, extending at least 1 km above the vent.
Figure 12. Reventador's 2004 lava flow/dome as seen on 28 November 2004.
The photo was taken looking W and downward from the cone's eastern crater
rim (see vantage point indicated by the star on figure 11). Courtesy of IG.
IG observers estimated that the total mid-December lava flow volume was ~3
x 10^6 m^3. The inferred 22 November date of flow onset would imply a
steady-state extrusion rate of ~0.1 x 10^6 m^3 per day and a flow front
advancing at ~80 m per day. These observations appear to conform with
satellite thermal infrared observations, which noted no significant
anomalies until the end of November, due presumably in large part to the
lava being confined within the steep-walled crater. Inclement weather
occurred and also may have impeded some of the satellite thermal observations.
The most recent visit to the crater rim, on 11 December 2004, traced the
source of degassing and lava outflow to the most elevated portion of a
small dome-like feature at the central western margin of the crater. Figure
13 shows how instrumentally aided nighttime incandescence observations
disclosed both the vent area and surficial flow-textures extending S
towards the southern breach of the cone. Figure 14 also documents a
comparatively narrow arm of lava trending towards the cone's northern
breach. Nighttime incandescence from the lava flow was also visible from
local communities such as El Chaco, ~20 km distant.
Figure 13. Thermal image of the lava flow in the interior of Reventador
crater taken with a Forward Looking Infrared (FLIR) imager at 2000 on 11
December 2004. Courtesy of IG.
Figure 14 illustrates the scene on 12 December 2004 during a visit to the
front of the most advanced lobe of lava (for location, see star at end of
flow lobe, figure 9). IG-EPN staff estimated the flow front at ~20 m high
and saw incandescent blocks falling off of it.
Figure 14. A N-looking view of Reventador's gray-colored lava-flow front
taken on 12 December 2004 at ~ 2,600 m elevation. Person at right indicates
scale of the advancing flow front. The lava flow emanated from the breach
in the S side of the cone's crater, a spot seen in the photo's upper left.
Courtesy of IG.
Background. Reventador is the most frequently active of a chain of
Ecuadorian volcanoes in the Cordillera Real, well E of the principal
volcanic axis. The forested dominantly andesitic stratovolcano rises to
3,562 m above the remote jungles of the western Amazon basin. A 4-km-wide
caldera widely breached to the E was formed by edifice collapse and is
partially filled by a young, unvegetated stratovolcano that rises about
1,300 m above the caldera floor to a height above the caldera rim.
Reventador has been the source of numerous lava flows as well as explosive
eruptions that were visible from Quito in historical time. Frequent lahars
in this region of heavy rainfall have constructed a debris plain on the
eastern floor of the caldera. The largest historical eruption at Reventador
took place in 2002, producing a 17-km-high eruption column, pyroclastic
flows that traveled up to 8 km, and lava flows from summit and flank vents.
Information Contacts: Patricio Ramon, Daniel Andrade, David Rivero,
Alexandra Alvarado, Sandro Vaca, and Pete Hall, Geophysical Institute (IG),
Escuela Politecnica Nacional, Apartado 17-01-2759, Quito, Ecuador (URL:
www.igepn.edu.ec/; Email: pramon@igepn.edu.ec;
dandrade@igepn.edu.ec; mhall@igepn.edu.ec); Jeffrey B. Johnson, Dept. of
Earth Sciences, James Hall University of New Hampshire, Durham, NH 03824
(jeff.johnson@unh.edu); MODIS Thermal Alert System, Hawaii Institute of
Geophysics and Planetology (HIGP), School of Ocean and Earth Science and
Technology, University of Hawaii at Manoa (URL:
www.modis.higp.hawaii.edu).
Fuego
Guatemala
14.47°N, 90.88°W; summit elev. 3,763 m
All times are local (= UTC - 6 hours)
Explosions and lava flows at Fuego continued after October 2003 (Bulletin
v. 28, no. 10). Similar activity prevailed through 2003 and 2004. This
report discusses events during November-December 2003 and includes a table
summarizing Fuego's 2003 behavior (table 3). A future report will discuss
2004 activity and will include a map showing critical place names. Several
pyroclastic flows occurred in 2003.
Table 3. Representative examples of reported volcanism at Fuego during
2003. Courtesy of INSIVUMEH.
Date - Lava flows, incandescent avalanches, and
pyroclasticflows (PFs)
- Ash column and ash fall
- Data source(s)
08 Jan 2003 - Lava flows. Two PFs (down Sta. Teresa drainage).
- Steam-and-ash to ~ 5.7 km a.s.l., drifted W.
- INSIVUMEH, CONRED, Washington VAAC, EFE via COMTEX,
Prensa Libra
Mid Jan 2003 - Incandescent avalanches down flanking canyons.
- ~ 2 km above summit, drifting S and SW, depositing
fine ash.
- INSIVUMEH, Washington VAAC
28 Apr-01 May - Incandescent avalanches.
- Intermittent ash eruptions, One ash plume reached ~
7 km a.s.l., blown SW
at 20-30 km/hour; some puffs visible over the coast.
- INSIVUMEH, Washington VAAC; US Air Force Weather Agency
29 Jun 2003 - Lava flows and avalanches down E flank
(incandescence seen from city of
Antigua and the coast). PFs extended ~ 1.5 km down
the W flank.
- Ash fell in villages to W and SE; Ash clouds to ~ 900 m.
- INSIVUMEH
09 Jul 2003 - Lava dome collapse PFs.
- Strong explosions sent ash to ~ 2 km above summit;
ash fell to W and SE
of summit.
- Washington VAAC, Prensa Libre
07 Aug 2003 - N/A
- A small ash emission seen on satellite imagery. The
ash cloud drifted NW
and covered an area about 3.5 by 3.5 km.
- Washington VAAC
08 Sep 2003 - N/A
- Ash plumes; one drifted S and covered an area of 5 x
5 km; another rose
to ~ 6 km a.s.l.
- Washington VAAC
09 Oct 2003 - N/A
- A pilot saw Fuego ash reaching ~ 4.6 a.s.l. No ash
was visible on
satellite imagery.
- Washington VAAC
17 Oct 2003 - Small incandescent avalanche down the Sta. Teresa
valley.
- A 33-minute-long eruption sent a gas-and-ash plume
to ~ 1.5 km above
the crater.
- INSIVUMEH
Nov-Dec 2003 - Incandescent avalanches.
- 4 November explosions threw material 150 m above
crater rim; 18-19
November, gas-and-ash plumes up to 1.2 km above the
crater; 28 Nov-1 Dec,
700-900 m above the crater; 7-9 December, 500 m
above crater; 10-16
December, 200-1000 m above the crater, and 18-22 and
30 December,
'low-level plumes.'
- INSIVUMEH
Tremor was common and at times abundant during 2003, including in the last
two months of the year. On 21 November, almost continuous harmonic tremor
was detected for a span of 21 hours. On 23 November intervals of tremor
lasted between 0.5 and 3 hours.
The Washington VAAC archive contains 48 ash advisories on Fuego. The number
of these advisories were as follows, during the stated months of 2003: 14
advisories in January (on the 8th, 9th, 11th, 12th, and 20th); 11 in April
(on the 17th, 28th, 29th, and 30th); eight in May (1st and 2nd); three in
June (30th), six in July (1st, 9th, and 10th), two in August (7th), two in
September (29th); and two in October (9th). The most impressive plumes
depicted in satellite-based graphics were for 28 April-1 May 2003, when
they often stretched well out to sea, reaching ~160 km SW from Fuego.
Otherwise, the graphics generally depicted much smaller plumes, in some
cases very local ones. The graphic for 28 September showed small plumes
from Fuego as well as simultaneous ones from Pacaya and Santa Maria.
Background. Volcan Fuego, one of Central America's most active volcanoes,
is one of three large stratovolcanoes overlooking Guatemala's former
capital, Antigua. The scarp of an older edifice, Meseta, lies between
3,763-m-high Fuego and its twin volcano to the N, Acatenango. Collapse of
the ancestral Meseta volcano about 8,500 years ago produced the massive
Escuintla debris-avalanche deposit, which extends about 50 km onto the
Pacific coastal plain. Growth of the modern Fuego volcano followed,
continuing the southward migration of volcanism that began at Acatenango.
In contrast to the mostly andesitic Acatenango volcano, eruptions at Fuego
have become more mafic with time, and most historical activity has produced
basaltic rocks. Frequent vigorous historical eruptions have been recorded
at Fuego since the onset of the Spanish era in 1524, and have produced
major ashfalls, along with occasional pyroclastic flows and lava flows.
Information Contacts: Instituto Nacional de Sismologia, Vulcanologia,
Meteorologia e Hidrologia (INSIVUMEH), Unit of Volcanology, Geologic
Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala
City, Guatemala (URL: www.insivumeh.gob.gt/); Washington Volcanic
Ash Advisory Center (VAAC), Satellite Analysis Branch, NOAA/NESDIS E/SP23,
NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746 USA
(URL: www.ssd.noaa.gov/); Charles R. Holliday, Air Force Weather
Agency, Offutt Air Force Base, Nebraska 68113 USA; Prensa Libre
(newspaper), 13 calle 9-31 zona 1, 01001 Guatemala City, Guatemala (URL:
www.prensalibre.com/).
__________________________________________________________
Global Volcanism Program, NHB E-421 Tel: (202) 633-1800
Smithsonian Institution Fax: (202) 357-2476
Washington, DC 20560-0119 Email: gvp@si.edu
Internet: www.volcano.si.edu/gvp/
GVN Bulletin, November 2004
****************************
From: Ed Venzke <venzke@volcano.si.edu>
Bulletin of the Global Volcanism Network
Volume 29, Number 11, November 2004
Andaman Islands (India) False reports of eruptions and confusion following
the M 9 earthquake
Ijen (Indonesia) News report cites increased activity beginning on 17 June 2004
Soputan (Indonesia) 12 December eruption covered villages with ash up to 2
cm thick
Manam (Papua New Guinea) Vigorous late-2004 eruptions cause 5 deaths and
lead to large evacuations
Erta Ale (Ethiopia) On 4-5 December 2004 visitors noted active hornitos but
solidified lava lake
Cotopaxi (Ecuador) Seismically quiet in January-April 2004; planning for
emergency water supplies
Reventador (Ecuador) Late 2004 visits find renewed venting and thick
intracaldera lava flows 2 km long
Fuego (Guatemala) Explosions and lava flows continued in November-December 2004
Dedicated to victims and survivors of the 26 December 2004 earthquake and
tsunami
As we go to press with this issue of the Bulletin our thoughts repeatedly
turn to the victims and survivors of the disastrous 26 December M 9
earthquake and tsunami. Although a different geologic process than we
discuss here, tsunamis are sometimes associated with volcanism. Conversely,
large earthquakes can trigger eruptions. The world has much to learn about
these and related geologic phenomena and about how to gauge, discuss, and
prepare for infrequent but potentially devastating events. We offer our
condolences and encouragement as we look towards a more integrated,
educated world.
Editors: Rick Wunderman, Edward Venzke, and Gari Mayberry
Volunteer Staff: Robert Andrews, Jacquelyn Gluck, William Henoch, and Aditi
Bhaskar
Andaman Islands
Indian Ocean, India
12.29°N, 93.88°E; summit elev. 305 m
All times are local (= UTC + 5 ½ hours)
False reports of volcanism surfaced describing eruptions at Barren Island
and Narcondum volcanoes (figure 1) following the 26 December 2004, M 9
earthquake off the W coast of northern Sumatra. Clarification was provided
by Dornadula Chandrasekharam of the Indian Institute of Technology. He
reported an absence of volcanic activity at these volcanoes, and at
Sumatran volcanoes, as recently as 4 January 2005.
Figure 1. A map of the Andaman Islands showing the only volcanoes known to
have erupted during the Holocene period (past 10,000 years), Narcondum and
Barren Island (N and B, respectively). Note that narrow straits break
Andaman island into multiple smaller islands (eg., Middle Andaman and
Baratang islands). Baratang Island contains an established, studied, active
mud volcano that reactivated after the M 9 earthquake.
The erroneous accounts were discovered by Chandrasekharam while watching
television news. He immediately contacted people in the Andaman region.
Upon learning that these reports were incorrect, he contacted media sources
and the Global Volcanism Network. Many Indian news sources that proclaimed
eruptions at Barren Island later withdrew their reports. The erroneous
information prevailed for a day to perhaps a week, although non-Indian news
agencies were slower to recognize and acknowledge the error.
Regional tectonic setting. Figure 2 illustrates the rudiments of the
regional tectonic setting, including the primary M 9 earthquake and
aftershocks for the next 10 days. The tectonic reconstructions are far more
complex than shown here, and the details are variously interpreted.
Figure 2. Map showing the broad tectonic setting on which Barren Island and
Narcondam volcanoes reside. The map began with the main shock of the M 9
earthquake and the earthquakes that followed during the next 11 days. USGS
preliminary tabulations computed the main shock as Mw 9.0 with a focus at
30 km depth.
In terms of local time (in the Andaman Islands and India, i.e. India
Standard Time), the epicenters shown occurred during the time interval
06:28:53 on 26 December to about 06:57 on 6 January. (In terms of UTC, this
represents the interval 00:58:53 on 25 December to about 19:57 on 5 January
2004). This digital map was extracted by applying a video simulation of
epicenters with time (Jones and others, 2002) to the recent seismic data.
The figure shows two prominent curving tectonic features crossing both
Java-Sumatra and the Andaman Sea (the Nicobar and Andaman Islands region).
One such curving feature is the volcanic front, on which lie all the active
volcanoes of Java and Sumatra, and farther N, Barren Island and Narcondam.
Outboard of that (to the W) is the second curving feature, the Sunda trench
and islands adjacent to it (the Andaman Islands, and islands to the W of
northern Sumatra hard-hit by the M 9 earthquake and tsunami). The trench
reflects the sea-floor expression of the subduction zone, and represents
the region where the M 9 earthquake occurred. The offset, often termed a
'megathrust,' involved 1,200 km of rupture along the subduction zone, and
suddenly shifted the Indian Ocean's floor ~15 m towards Sumatra (Hopkin, 2005).
Regarding the M 9 earthquake, according to the USGS, the local time and
date in terms of local time in N Sumatra at the epicenter was Sunday, 26
December 2004 at 07:58:53 (i.e., roughly 8 am). The USGS provided a table
showing the time of the main shock in a variety of time zones.
Some excellent tutorials have provided background on the tectonic setting,
the earthquake, and the tsunami. These have appeared in the press and on
the web (eg. Sieh, 2004, 2005; NOAA, www.noaa.gov/tsunamis.html).
Although large earthquakes may trigger volcanism (Linde and Sacks, 1998),
so far this does not appear to be the case, at least at the volcanoes of
Barren Island and Narcondum.
Mud volcanoes and ensuing confusion. Post-earthquake reports of active 'mud
volcanoes' in the Andaman Islands caused panic and confusion in the region,
and came at a particularly bad time. Chandrasekharam pointed out that in
Andaman, like many other arc provinces, several mud volcanoes are present.
These are not real volcanoes in the usual sense, but because they may build
a small, low-profile cone of local extent around the hole through which the
mud is thrown out, they are known as mud volcanoes (figure 3).
Figure 3. A 2003 photograph showing about a quarter to one half of a mud
volcano on Baratang island (top) and its largest crater (~ 20 cm in
diameter, ~ 28 cm in depth) (bottom). This site was known as a minor
fissure prior to 1983; but in that year the largest outburst occurred,
chiefly emitting warm (~ 30°C) mud. Mud again began emerging in February
2003. The dominant feature was a sub-circular mound of mud, ~ 30 m in
diameter with a height of ~ 2 m at the center. Observers noted a colorless,
sulfurous smelling gas. The mud contained angular to sub-rounded rock
fragments from underlying strata. No photos nor similarly detailed
technical reports have been received showing alleged recent activity that
began 27 December 2004 (see text for news report). All photos and data
courtesy of the Geological Survey of India, Eastern Region.
Some of the difficulty with the news reports was that the mud volcanoes'
locations, numbers, and impacts remained vague, and that Barren Island
became intertwined with story. An extreme example came from an
irresponsible report in the tabloid India Daily (2 January 2005), which
contained the title "Volcano[es] Barren-1 and Narcondam erupt in
Andaman--Seismic disturbance can cause more tsunami." It continued with
wild claims such as, "Severe seismic activities are seen in these islands .
. . personnel who have reached these remote areas are facing shattering
earth vibrations and high waves," and "Some scientists are predicting
severe earthquake again in the North of Andaman Nicobar Islands. The effect
can be severe on Myanmar, Andaman, Indi[a]'s east coast, Bangladesh and
Sumatra . . .." They added, "Andaman's tribals strangely are unaffected as
most of them somehow went [to] higher ground before the tsunami. So did the
animals." Science journalism clearly has a lot to compete with (see
Oldenburg, 2005, for more discussion of these topics).
One alleged mud volcano 'Barren-1' has a name so close to the volcano's
name (Barren Island) that it was frequently confused. The mud volcano's
name (if there is one) appears to be absent from the technical literature
at the Geological Survey of India's website.
On a positive note, one mud volcano received consistent mention in a number
of news articles and provided coverage generally congruent with geological
data posted by the Geological Survey of India. According to an article in
India News (with the leader, "Port Blair, 30 December"), "A mud volcano at
the inhabited Baratang Island in Middle Andaman has erupted but the
administration said there was no cause for concern. 'Mud keeps bubbling in
the volcano, but on December 28, the eruption was up to three meters and
there was considerable heat,' Inspector General of Police S. B. Deol said
here."
"He [also] said the mud volcano was located on one side of the Baratang
Island, which was about 100 km from Port Blair. People live on the other
side, but there is no cause for concern."
A report in the India Daily was nearly identical. Details on a Geological
Survey of India website noted that the Baratang mud volcano began erupting
on 27 December 2003 (figure 3 and caption). Mud volcanoes may have also
occurred elsewhere in the region, but the available news reports
consistently failed to disclose locations.
Often associated with active faults and with petroleum fields, mud
volcanoes on land consist of low-lying surface mud extrusions that vary in
size from meters to several kilometers across. They emit mud at
temperatures significantly below magmatic, which are typically at least
800°C. Eruptions from mud volcanoes can reach heights of several hundred
meters and consist of mud, fluids and gases, and sometimes burning
hydrocarbons. Although in submarine environments mud volcanoes can be
extensive, deadly mud volcano eruptions are extremely rare because their
eruptions seldom move far enough to affect large areas of the land
surface. Their greatest danger may be to curious onlookers who venture too
close.
References. Jones, A., Siebert, L., Kimberly, P., and Luhr, J.F., 2002,
Earthquakes and Eruptions, v. 2.0 (CD-ROM): Smithsonian Institution, Global
Volcanism Program, Digital Information Series, GVP-2.
Hopkin, M., 2005, Triple slip of tectonic plates caused seafloor surge:
Nature, v. 433, no. 3 (06 Jan 2005).
Linde, A.T., and Sacks, I.S., 1998, Triggering of volcanic eruptions:
Nature, v. 395, p. 888-890.
Oldenburg, D., 2005, A sense of doom: Animal instinct for
disaster--Scientists investigate wildlife's possible warning systems: The
Washington Post (8 January 2005), p. C1, C3 (URL:
www.washingtonpost.com/).
Sieh, K., 2004, The science behind the Aceh earthquake: Caltech Media
Relations (30 December 2004), (URL:
pr.caltech.edu/media/Pres...2628.html).
Sieh, K., 2005, In Sumatra: Notes From a Geologist in the Field: Caltech
Today (1 January 2005; URL: today.caltech.edu/today/).
U.S. National Earthquake Information Center (NEIC) (URL:
earthquake.usgs.gov)./
U.S. National Oceanic and Atmospheric Administration (NOAA) (URL:
www.noaa.gov/tsunamis.html).
Background. Barren Island, a possession of India in the Andaman Sea about
135 km NE of Port Blair in the Andaman Islands, is the only historically
active volcano along the N-S-trending volcanic arc extending between
Sumatra and Burma (Myanmar). The 354-m-high island is the emergent summit
of a volcano that rises from a depth of about 2,250 m. The small,
uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with
walls 250-350 m high. The caldera, which is open to the sea on the W, was
created during a major explosive eruption in the late Pleistocene that
produced pyroclastic-flow and -surge deposits. The morphology of a fresh
pyroclastic cone that was constructed in the center of the caldera has
varied during the course of historical eruptions. Lava flows fill much of
the caldera floor and have reached the sea along the western coast during
eruptions in the 19th century and more recently in 1991 and 1995.
Narcondum volcano, an island possession of India in the Andaman Sea, is
part of a volcanic arc that continues northward from Sumatra to Burma
(Myanmar). The small 3 x 4 km wide conical island, located about 130 km
east of North Andaman Island, rises to 710 m, but its base lies an
additional 1,000 m beneath the sea. The island is densely vegetated,
bounded by cliffs on the southern side, and capped by three peaks. No
evidence of historical volcanism is present, although the summit region is
less densely vegetated and volcanism at the andesitic volcano is considered
to have continued into the Holocene. The island's name means "pit of hell,"
although the name could have been mistakenly transferred from the
historically active Barren Island volcano, 140 km to the SSW.
Information Contacts: Dornadula Chandrasekharam, Department of Earth
Sciences, Indian Institute of Technology, Bombay 400076, India (URL:
www.geos.iitb. ac.in/dchandra/biexp/, Email: dchandra@iitb.ac.in);
India News (URL: news.newkerala.com/india-news/); India Daily (URL:
www.indiadaily.com/); The Washington Post, Washington DC, USA (URL:
www.washingtonpost.com/); Geological Survey of India, 27 Jawaharlal
Nehru road, Kolkata (Calcutta) 700016, India.
Ijen
eastern Java, Indonesia
8.058°S, 114.242°E; summit elev. 2,386 m
All times are local (= UTC + 7 hours)
The Chief of the local National Park has been quoted as having reported an
increase in activity beginning on 17 June 2004. This resulted in closing
the area to visitors. Reuters quotes him as having said "There have been
sulfuric rocks coming out of the edge of the crater and the fluid in it
(the crater lake) has turned from green to white and has emitted hot foam.
There are also increasing tremors."
Background. The Ijen volcano complex at the eastern end of Java consists of
a group of small stratovolcanoes constructed within the large 20-km-wide
Ijen (Kendeng) caldera. The N caldera wall forms a prominent arcuate ridge,
but elsewhere the caldera rim is buried by post-caldera volcanoes,
including Gunung Merapi stratovolcano, which forms the 2,799-m-high point
of the Ijen complex. Immediately W of Gunung Merapi is the renowned
historically active Kawah Ijen volcano, which contains a nearly 1-km-wide,
turquoise-colored, acid crater lake. Picturesque Kawah Ijen is the world's
largest highly acidic lake and is the site of a labor-intensive sulfur
mining operation in which sulfur-laden baskets are hand-carried from the
crater floor. Many other post-caldera cones and craters are located within
the caldera or along its rim. The largest concentration of post-caldera
cones forms an E- to W-trending zone across the southern side of the
caldera. Coffee plantations cover much of the Ijen caldera floor, and
tourists are drawn to its waterfalls, hot springs, and dramatic volcanic
scenery.
Information Contact: Reuters News Service.
Soputan
Sulawesi, Indonesia
1.11°N, 124.73°E; summit elev. 1,784 m
All times are local (= UTC + 8 hours)
Soputan erupted again on 12 December 2004. The Directorate of Volcanology
and Geological Hazard Mitigation (DVGHM) noted that an eruption on 18
October 2004 sent a cloud ~600 meters above the crater. The previous
eruptive episode occurred during July and August 2003 (Bulletin v. 28, nos.
8, 10, and 11). A summary of ash plumes from mid-2003 through 12 December
2004 appears in table 1. Large discrepancies appeared in reported ash
column heights; with the satellite estimates about 10 times larger than
ground-based estimates.
Table 1. Reported ash plume altitudes recorded from Soputan, 18 July
2003-12 December 2004. Courtesy of DVGHM and Darwin VAAC.
Date Height (km) (comment) Source
18 Jul 2003 ~ 2 km above summit DVGHM
02 Sep 2003 ~ 2 km altitude Darwin VAAC
04 Sep 2003 ~ 3 km altitude Satellite imagery, Darwin VAAC
(extending ~ 75 km N
of the summit)
18 Oct 2004 ~ 600 m above summit DVGHM
12 Dec 2004 ~ 1 km above summit DVGHM
12 Dec 2004 ~ 10.7 km altitude Darwin VAAC
The earliest details mentioned by DVGHM regarding the 2004 activity
discussed 11 December 2004, a time when the tremor tended to rise,
attaining peak-to-peak amplitudes of 0.5-3.0 mm. Observers also saw
incandescence at the crater's rim.
At 0046 on 12 December tremor again registered with maximum peak-to-peak
amplitudes of ~45 mm. At 0050 on 12 December Soputan erupted, sending an
ash cloud up to 1 km. This was followed by discharge of a "hot cloud"
(pyroclastic flow ?) to a distance of ~200 m E (from 'Aeseput,' a prominent
NE-flank vent that formed in 1906). A lava flow spread W and S of Soputan.
Observers could hear rumbling noise and thunder from their monitoring
station ~11 km from the crater.
White-to-gray ash went E. At 0130 on 12 December a problem arose with the
seismic sensors, perhaps because the solar panel was covered with ash. By
0600 the sensor was down. At 0500 that day a hot cloud occurred with a run
out distance of ~150 m and a height of 200 m. Activity persisted until
1030. Soputan's summit then became visually obscured by clouds, but
observers could still make out a white thin-to-medium plume to 70-80 m
above the crater, and incandescence.
On the 13 December at 1752 observers felt an earthquake with a magnitude of
MM I-II. The seismograph was then still inoperable.
News reports. A 13 December news report in The Daily Reform Voice stated
that hundreds of hectares of paddy-fields and other agricultural land to
the W of the Soputan was seriously impacted by tephra.
Thomas Dobat, a German expatriat living in Indonesia and concerned about
the situation, sent Bulletin editors a translation of a 13 December 2004
article on Soputan taken from the Indonesian Journal Komentar. Similar to
the above report, it also noted that hundreds of villages in 13 districts
in Central Minahasa and in South Minahasa suffered from tephra fall emitted
on 11-12 December. These eruptions of Soputan were accompanied by heavy
thunder and lightning, which were heard in the town of Amurang.
Ash fell in nearly all of Central Minahasa and in parts of South Minahasa.
The result was that in all areas of Central Minahasa, especially in the
town of Tondano, houses, rice-fields, and roads were ash-covered up to 2 cm
thick.
Background. The small Soputan stratovolcano on the southern rim of the
Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of
Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano
rises to 1784 m and is located SW of Sempu volcano. It was constructed at
the southern end of a SSW-NNE trending line of vents. During historical
time the locus of eruptions has included both the summit crater and
Aeseput, a prominent NE-flank vent that formed in 1906 and was the source
of intermittent major lava flows until 1924.
Information Contacts: Directorate of Volcanology and Geological Hazard
Mitigation, Jalan Diponegoro 57, Bandung 40122, Indonesia (Email:
dali@vsi.dpe.go.id; URL: www.vsi.esdm.go.id/); Darwin Volcanic Ash
Advisory Centre, Australian Bureau of Meteorology (URL:
www.bom.gov.au/info/vaac); The Daily Reform Voice; Komentar; Thomas
Dobat, Lorong Jerman, Kauditan II, 95372, Sulawesi Utara, Indonesia.
Manam
Papua New Guinea, Northeast of New Guinea
4.10°S, 145.061°E; summit elev. 1,807 m
All times are local (= UTC - 10 hours)
Several periods of eruption took place on the island of Manam during the
last months of 2004. Rabaul Volcano Observatory (RVO) noted outbursts
during 24-31 October (Bulletin v. 29, no. 10), 10-12 November, and on 6
December. Several other plumes were noted as well. Satellite-based alerts
(MODVOLC) were noteworthy during this interval, having been absent for over
9 months.
On 6 December, the newspaper The National reported that these eruptions had
killed five people, whose deaths were primarily related to respiratory
complications from inhaling volcanic material. Volcanic ash damaged crops,
water supplies, and houses. News accounts discussed evacuations, with the
possibility of evacuating all or most of the island (figure 4). The news
also mentioned food shortages after the 24 October eruption.
Figure 4. Geography of the area around Manam showing two named villages on
the island and numerous settlements on the main island of New Guinea. For
scale, Manam Island is ~ 10 km in diameter. The volcano is sometimes
referred to as Mount Iabu in the regional press. The city of Wewak lies off
the map, ~ 160 km W of Manam; the city of Madang lies ~ 150 km to the E.
The large meandering river at left is the Sepik. The island's residents, a
total of 9,467 people, rely on subsistence farming and fishing for food,
and copra and cocoa as a source of income. Map courtesy of Jorgen Aabech.
The government of Papua New Guinea presented a new website, The National
Disaster Center, which broadly disseminates government disaster information
including volcano reports and updates (see URL under Information Contacts,
below). The website contained a Manam hazards map. Other documents on that
site noted shifting winds and the lack of a clearly safe area on the island
during the late 2004 crisis. It said that the government would sponsor
large-scale evacuations beginning on 27 November 2004.
The eruptive episode that began on 24 October continued at least a week
(figure 5). By 31 October, the eruption at Main Crater consisted of
Strombolian activity, with ash and scoria emissions. Tephra of ~1 cm
diameter were deposited in Warisi village on the SE side of the island.
Small pyroclastic flows were generated, and fresh lava flowed into the NE
radial valley. The lava flow followed the Boakure side of the valley,
covering older flows from the 1992-1994 eruption. Beginning on the morning
of the 31st, the amount of continuous volcanic tremor increased to
moderate-to-high levels, so the Alert Level was increased from Stage 1 to
Stage 2. Villagers were advised to remain away from Manam's four main
radial valleys.
Figure 5. Image of Manam and vicinity acquired on 24 October 2004 by the
Moderate Resolution Imaging Spectroradiometer (MODIS), an instrument on the
Terra satellite of the National Aeronautics and Space Administration
(NASA). Dark ash rising from Manam drifted NW along and then away from the
N coast of the main island, New Guinea. Courtesy NASA Earth Observatory.
The Darwin Volcanic Ash Advisory Center reported the 24 October outburst
(Bulletin v. 29, no. 11). On 31 October during 0813-1449 they noted a plume
at ~13.7 km altitude drifting SE on visible satellite imagery. The Aviation
Color Code was at Red, the highest level.
According to a news report, ". . . [~0.3 m] of ash with hot pumice" landed
on the roofs of houses, and ash drifted as far W as Wewak, ~100 km away.
Reportedly, ~4,000 villagers moved to safer areas.
On 2 November around 2325 a possible eruption may have produced a plume to
~7.6 km altitude, which drifted SE. Ash was visible on satellite imagery on
8 and 9 November at an altitude of ~3 km; on 9 November the plume extended,
~55 km to the NE.
A Strombolian eruption occurred during 10-11 November 2004. The ash column
from the eruption was estimated to have risen ~5-6 km above the crater, and
perhaps rose as high as ~9 km above the crater, according to an Air Niugini
pilot. The activity was accompanied by continuous weak to moderate roaring
and rumbling noises and frequent loud explosions. Light ash and scoria fall
was reported near local villages. As of 2130 on 10 November ash reached 7
km altitude and 147 km to the SW. As of 12 November, the ash emissions
reached 10 km altitude and extended laterally 74 km W to NW of the volcano.
During this reporting interval Darwin VAAC noted that a SE-drifting plume
was visible on satellite imagery on 31 October during 0813-1449 at an
altitude of ~13.7 km.
A satellite image from the Terra Moderate Resolution Imaging
Spectroradiometer (MODIS) on 15 November shows a large brown ash plume
blowing SW (figure 6).
Figure 6. Manam image acquired 15 November 2004 from Moderate Resolution
Imaging Spectroradiometer (MODIS) passing overhead on the National Aviation
and Space Agency (NASA) Terra satellite. Dark ash rises from Manam and
drifts SW over New Guinea. Courtesy NASA Earth Observatory.
According to RVO scientists, on 23-24 November Main Crater ejected glowing
lava and discharged an ash cloud that rose ~10 km high. A lava flow was
also reported to be heading for two villages on the island. At 1850 on 23
November, a phase of strong Strombolian eruption began producing a
continuous, thick ash column that rose about 10 km above the summit. The
ash cloud emissions were accompanied by projection of glowing lava
fragments, loud roaring and rumbling noises, and occasional loud and
banging noises that produced shock waves. A continuous bright red glow
visible down the NE valley indicated emplacement of a lava flow.
The lava flow was reported heading NE towards villages of Kolang and Bokure
1. In addition to the lava, Manam emitted large rocks. Around this time the
aviation red alert issued for aircraft noted that the ash plume extended
130 km SE of Manam.
Press accounts stated that emergency officials said an area was being
cleared on the mainland for a possible full-scale evacuation of Manam's
~9,500 islanders. Evacuation was to become compulsory if activity
intensified from Stage 3 (which was set by 22 November) to Stage 4. Some 20
bush homes had collapsed due to 'mud rain' (presumably, falling tephra),
and five people had been injured.
RVO reported that a slight increase in eruptive activity from Main Crater
began after 1600 on 26 November, which continued until 0800 on the 29th.
Summit activity consisted of continuous forceful emission of thick dark
gray ash clouds that rose less than 1 km above the summit before being
blown NW. Fine ashfall to the NW at Zogari and Iassa villages was reported
from about 1700. A single weak roar was heard between 0600 and 0700 on the
27th.
Seismicity was moderate to moderate-high at 2300 on the 26th and 0800 on
the 27th. Volcanic tremors continued to be recorded suggesting the system
remained dynamic and capable of ongoing variable eruptions, with sporadic
more vigorous phases.
On 28-29 November, RVO reported that ash clouds were rising less than 1 km
above the summit before being blown by the shifting NNE and NNW winds. Fine
ashfall was reported at Warisi. Weak roaring noises were heard between
1900-2400 on the 28th. A weak glow with weak projections of incandescent
lava fragments was visible during the night of the 28th, and Southern
Crater released thin white vapor only.
Some press reports described 7,900 persons evacuated from Manam. According
to the Planet Diary web site, about 9,000 people were evacuated by 1
December 2004 as the eruption grew more violent.
Mid-afternoon on 5 December RVO noted a slight change in activity at
Southern Crater marked by commencement of sub-continuous weak to moderate
roaring and rumbling noises. The noises continued until 1000 that day. As
darkness fell, intervals of visibility occurred (eg., during 1800-1808,
2030-2108, and 2130-2200); observers saw sub-continuous lava fountaining.
Meanwhile, from Main Crater there came a series of sub-continuous,
forceful, moderately thick, gray-brown ash-laden clouds, which were
occasionally visible above the weather clouds. The ash plume rose between
about 600 and 900 m above the summit and drifted to the E and NE. Light
ashfall and fine scoria fell at the villages Abaria and Bokure 1.
Fluctuating audible noises consisted of low roars, 'jet engine' roars, and
occasional still-louder roars. Although visibility was generally poor due
to volcanic ash clouds from both craters, observers could still make out
variable glow coming from the craters.
On 8 December 2004, The National reported that, according to RVO, Manam
erupted starting on the morning of 6 December. Fist-sized scoria were
thrown out of the vent into the air, hitting houses in the villages below.
The eruption began at 0800 and peaked at 1150 with "seismicity continuing."
The National also reported that a pyroclastic flow occurred in the SE
valley during the 6 December eruption, with ash and cloud directed NW. On
the 6th, residents of Madang (~150 km E of Manam) described feeling tremor
or ground motion; those in Wewak (~160 km to the W) reported similar
sensations and also noted volcanically derived dust. Although ash from 6
December was apparently widespread, Googling for news of Manam ash in Irian
Jaya failed to turn up any reports from there.
The Darwin VAAC reported ash plume sightings from satellites during 12-14
December, and the RVO reported moderate eruptions continuing in that period.
Fatalities. An article by Bonney Bonsella in The National showed pictures
of Manam Islanders in evacuation. They waded through shallow surf to board
through the open bow of a large beached landing craft. The article
discussed fatalities during the eruption.
"The volcanic eruption on Manam Island in the Madang province has so far
claimed five lives-two elderly women and three children between the ages of
5-13. The coordinator of the Manam evacuation exercise Camillus Dugumi
confirmed the deaths, adding that the deaths were linked to respiratory
complications resulting from inhaling volcanic ashes and dust. Mr Dugumi,
who is also the district health programme manager, said one of the deaths
was that of an elderly women from Bokure village recorded early last week
at the Bogia District hospital. The women died after being admitted to the
hospital for respiratory complications. One child, a little boy, died on
Friday at the Asuramba care centre after suffering pneumonia."
"Three others-an adult women and two other children-had died during earlier
volcanic activity on Manam."
Displaced residents. The above-mentioned article related that three
State-owned plantations (called Asuramba, Potsdam, and Magem (and Daigul?))
were set aside, ". . . at least for the time being[,] to accommodate a
speedy resettlement of the displaced Manam islanders." Another news article
noted that these plantations are near the town of Bogia (figure 4). The
National Disaster Center website noted that "The three plantations were
bought off from the lessee in 1995 for K1.25 million following a National
Executive Council decision for the purpose of resettlement of Manam
Islanders displaced by volcanic activity." Controversies remain with
respect to land issues. Still , that website noted that the long-term
solution advocated by the President, Manam Local Level Government is to
resettle the people of Manam on the mainland. For this purpose the
Provincial Disaster Committee has identified State land to resettle the
Manam Island people.
MODVOLC. The MODIS infrared instrument flown on the NASA Terra and Aqua
satellites showed an impressive set of thermal alerts beginning 21 October
2004 (figure 7). Since the beginning of MODVOLC operations (Bulletin v. 28,
no. 1) thermal alerts occurred at Manam during only two periods. The first,
7 April-21 May 2002, was related to increased Strombolian activity
(Bulletin v. 27, no. 5). The second period, 21 October until at least 14
December 2004, was associated with the current crisis and was a time when
alert ratios and summed radiances reached higher values than during the
first period. These parameters are consistent with a highly active vent
and/or lava flows, and in accord with vigorous Strombolian emissions seen
in the field.
Figure 7. MODVOLC thermal alert ratios, number of alert pixels, and summed
4 mm radiance plots for Manam from 1 January 2001 until 31 December 2004.
Alerts occurred only between 7 April and 21 May 2002 and between 21 October
and 14 December 2004. Thermal alerts collated by Charlotte Saunders, and
David Rothery; data courtesy of the Hawaii Institute of Geophysics and
Planetology's MODIS thermal alert team.
This analysis of MODIS thermal alerts (using the MODVOLC alert-detection
algorithm) is based on data extracted from the MODIS Thermal Alerts website
maintained by the University of Hawaii HIGP MODIS Thermal Alerts team.
Thermal alerts are based on an 'alert ratio,' and an alert is triggered
whenever this ratio has a value more positive than -0.8. This threshold
value was chosen empirically by inspection of images containing known
volcanic sites at high temperature, and is the most negative value that
avoids numerous false alarms. There are also some day-time alerts, which
are based on the same algorithm but incorporating a correction for
estimated solar reflection and a more stringent threshold whereby the alert
ratio is required to be more positive than -0.6 in order to trigger an alert.
Background. The 10-km-wide island of Manam, lying 13 km off the northern
coast of the mainland Papua New Guinea, is one of the country's most active
volcanoes. Four large radial valleys extend from the unvegetated summit of
the conical 1,807-m-high basaltic-andesitic stratovolcano to its lower
flanks. These "avalanche valleys," regularly spaced 90 degrees apart,
channel lava flows and pyroclastic avalanches that have sometimes reached
the coast. Five small satellitic centers are located near the island's
shoreline on the northern, southern and western sides. Two summit craters
are present; both are active, although most historical eruptions have
originated from the southern crater, concentrating eruptive products during
the past century into the SE avalanche valley. Frequent historical
eruptions have been recorded at Manam since 1616. A major eruption in 1919
produced pyroclastic flows that reached the coast, and in 1957-58
pyroclastic flows descended all four radial valleys. Lava flows reached the
sea in 1946-47 and 1958.
Information Contacts: Rabaul Volcano Observatory (RVO), P.O. Box 386,
Rabaul, Papua New Guinea; National Disaster Centre, Department of
Provincial Affairs and Local Level Government (Ministry of Inter-Government
Relations), PO Box 4970, Boroko, National Capital District, Papua New
Guinea (URL: www.pngndc.gov.pg/); David Innes, Flight Safety Office,
Air Niugini (Email: dinnes@airniugini.com.pg or deejayinnes@yahoo.com);
Andrew Tupper, Darwin Volcanic Ash Advisory Centre, Australian Bureau of
Meteorology (URL: www.bom.gov.au/info/vaac); Jorgen Aabech,
Skogbrynet 40B, N-1709 Sarpsborg, Norway (Email: Jorgen.aabech@eunet.no;
URL: http:// www.vulkaner.no); MODIS Thermal Alert System, Hawaii Institute
of Geophysics and Planetology (HIGP), School of Ocean and Earth Science and
Technology, University of Hawaii at Manoa (URL:
www.modis.higp.hawaii.edu); David Rothery and Charlotte Saunders,
Department of Earth Sciences, The Open University, Milton Keynes, MK7 6AA,
United Kingdom (Email: d.a.rothery@open.ac.uk); Kevin Pamba and Bonney
Bonsella, The National (URL: www.thenational.com.pg/1206/).
Erta Ale
Ethiopia
13.60°N, 40.67°E; summit elev. 613 m
Two teams sent reports on Erta Ale's behavior in December 2004. On 1-5
December the visiting team included Jacques-Marie Bardintzeff and a group
from Ushuaia Nature, and on 4-5 December the team consisted of the
volcanology travel group SVE-SVG. Both groups submitted similar reports and
commented on substantial changes they observed compared to conditions
described in past reports (most recently, Bulletin v. 29, no. 8). Although
Erta Ale frequently contains a lava lake with an open surface of molten
lava, that was not the case this time.
The lava lake's surface had chilled within the small (~200-m-diameter) S
pit crater (figure 8). A solidified lava crust covered the crater floor.
The crust's surface sat ~15 m below the W crater rim, and ~30 m below the E
crater rim. On top of this crust stood four coalesced hornitos in the SE
part of the S crater (figure 9). They were ~10 m high and represented the
only portion of the crust where molten material was in evidence. Two
hornitos emitted high temperature (more than 500°C) SO2-rich gas. Another
hornito contained glowing molten lava. During the night of 4 December the
SVE-SVG group saw degassing and incandescent lava at the summit of two of
these hornitos. Bardintzeff described sampling molten material from 12 m
depth, in one of the hornitos using a cable and an iron mass (figure 9).
Figure 8. The small S pit crater at Erta Ale as viewed from the E on 5
December 2004. Hornitos had grown on the W part of the crater floor; except
for these windows into the molten material at depth, the rest of the lava
lake surface had completely solidified. Photo provided by J. M. Bardintzeff.
Figure 9. The S pit crater at Erta Ale as seen from the W on 5 December
2004, with the 4 hornitos in the center of the photo. Two hornitos on the
left emitted high temperature SO2. The hornito in the right foreground
contained molten lava (which was sampled). Photo provided by J. M. Bardintzeff.
The SVE-SVG team noted recent activity within the North crater, where an
uplifted area termed a 'lava bulge' had solidified. It covered ~80% of the
crater floor and rose to about 20-25 m below the crater rim. In the lava
bulge's central area, strong and noisy degassing of SO2 spouted from
several small hornitos. At the bulge's periphery the observers saw ten
small incandescent vents. Subsequently, two plumes rose above the volcano.
Background. Erta Ale is an isolated basaltic shield volcano that is the
most active volcano in Ethiopia. The broad, 50-km-wide volcano rises more
than 600 m from below sea level in the barren Danakil depression. Erta Ale
is the namesake and most prominent feature of the Erta Ale range. The
613-m-high volcano contains a 0.7 x 1.6 km, elliptical summit crater
housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide
depression elongated parallel to the trend of the Erta Ale range is located
to the SE of the summit and is bounded by curvilinear fault scarps on the
SE side. Fresh-looking basaltic lava flows from these fissures have poured
into the caldera and locally overflowed its rim. The summit caldera is
renowned for one, or sometimes two long-term lava lakes that have been
active since at least 1967, or possibly since 1906. Recent fissure
eruptions have occurred on the northern flank of Erta Ale.
Information Contacts: Jacques-Marie Bardintzeff, Laboratoire de
Petrographie-Volcanologie, Bât. 504, Universite Paris-Sud, F-91405, Orsay,
France (Email: bardizef@geol.u-psud.fr, URL:
www.lave-volcans.com/bardintzeff.html); Henry Gaudru, Societe
Volcanologique Europeenne (SVE), C.P.1-1211 Geneva 17- Switzerland (Email:
HgaudruSVE@compuserve.com; URL: www.sveurop.org/).
Cotopaxi
Ecuador
0.677°S, 78.436°W; summit elev. 5,911 m
All times are local (= UTC - 5 hours)
Seismicity at Cotopaxi during December 2003 through December 2004 yielded
averages that generally remained within normal levels (table 2). Steam
emissions continued, and sulfurous odors were occasionally reported. A plot
of total seismicity each week during 2001-July 2004 portrayed numerous
peaks and valleys in the range 50-200 events per week. Occasional
excursions took the weekly totals to several hundred events in late 2001
and early 2002 (peaking at over 700 events per week during mid-October
2001). The 2004 data lacked such dramatic excursions.
Table 2. Annual summaries showing typical daily averages of various kinds
of seismicity at Cotopaxi during 2001-2004. Courtesy of IG (shown on their
website in the January 2005 report).
Year Volcano-tectonic Hybrid Long-period Tornillo
Tremor Total
2001 3.1 1.0 10.2 0.1 0.2
11.3
2002 2.9 3.0 14.6 0.1 0.4
18.2
2003 1.2 3.7 9.3 0.0 1.4
14.2
2004 0.41 3.59 11.10 0.0 1.56
15.11
Planning for emergency water supplies. Although seismicity and other
monitored parameters were moderate to low during most of 2003 (Bulletin v.
28, nos.11 and 12), local authorities worked on a contingency plan for
emergency drinking water in the event of a crisis at Cotopaxi.
The Quito metropolitan sanitation and drinking water company (EMAAP-Q)
prepared a contingency plan for residents around Cotopaxi. The challenge
was to provide for sufficient amounts of potable and sanitation water for
some half a million people in the event of an eruption that contaminates
their normal water supplies. This contingency plan was drawn up using
experience gained from the operational emergency plan used to recover from
the eruption in 1998-99 and the Reventador eruption in 2002.
During the Guagua Pichincha eruption, pyroclastic material impacted Quito,
and ash fell into the water treatment plants and threatened the water
supply systems. EMAAP-Q developed an operational and emergency plan. The
plan was tested in 1999 when the volcano had two major eruptions that heat
dropped ash on Quito and its infrastructure.
Background. Symmetrical, glacier-clad Cotopaxi stratovolcano is Ecuador's
most well-known volcano and one of its most active. The steep-sided cone is
capped by nested summit craters, the largest of which is about 550 x 800 m
in diameter. Deep valleys scoured by lahars radiate from the summit of the
andesitic volcano, and large andesitic lava flows extend as far as the base
of Cotopaxi. The modern conical volcano has been constructed since a major
edifice collapse sometime prior to about 5,000 years ago. Pyroclastic flows
(often confused in historical accounts with lava flows) have accompanied
many explosive eruptions of Cotopaxi, and lahars have frequently devastated
adjacent valleys. The most violent historical eruptions took place in 1744,
1768, and 1877. Pyroclastic flows descended all sides of the volcano in
1877, and lahars traveled more than 100 km into the Pacific Ocean and
western Amazon basin. The last significant eruption of Cotopaxi took place
in 1904.
Information Contact: Geophysical Institute (IG), Escuela Politecnica
Nacional, Apartado 17-01-2759, Quito, Ecuador (URL: www.igepn.edu.ec/).
Reventador
Ecuador
0.078°S, 77.656°W, summit elev. 3,562 m
All times are local (= UTC - 5 hours)
A 16 December 2004 report from the Instituto Geofisico (IG) of the Escuela
Politecnica Nacional calls attention to renewed lava effusion from the
crater that lies within Reventador's large summit cone (figure 10). A
block-lava flow escaped the cone's crater. It ran out at a breach in the S
wall, and by 16 December it had advanced ~2 km farther. The flow advanced
SE along a narrow, E-curving path, remaining atop lavas from 2002. Thus far
in 2004, lava flows remained well within the larger caldera.
Figure 10. An aerial photo of Reventador's 4-km-diameter caldera as a base
for mapping the lava flows of 2002 and those of 2004 through mid-December.
The 2002 flows are labeled Lava 1 and Lava 2. The 2004 lava flow followed
and partly covered Lava 1. At a distance of ~ 1 km from the vent, the 2004
lava flow bifurcated into two closely spaced parallel lobes. The caldera
has an E-tilting floor, is open on its E side, and contains a prominent
cone on its W side. The cone forms the volcano's summit, and contains an
elongate crater that hosts the 2004 vent ("active vent"). The crater has a
rim that is indicated by a solid curving line; the crater's inward-sloping
walls are indicated by light shading and lines resembling the trends of
gullies. The cone's floor at its southern breach lies at ~ 3,200 m
elevation. The aerial photo was taken by Instituto Geografico Militar in
1983. Figure courtesy of IG.
Reports in 2003 chiefly discussed events outside the caldera. A road, one
gas pipeline, and two oil pipelines traverse Reventador's flanks 7 km ESE
of the active vent. All of these installations were affected in 2003 (but
not appreciably since then). The pipelines were destroyed due to heavy
lahars coming down the Reventador river on 6 May 2003 (Bulletin v. 28, no.
6). Our last report (Bulletin v. 28, no. 11) discussed events during July
through most of November 2003.
Lava venting in the crater likely began in early November 2004, a time when
seismic station CONE registered dramatic increases in volcano-tectonic
events (figure 11). In response to the elevated seismicity, the IG-EPN
began more intensive monitoring, including overflights with thermal
imaging, repeat visits to the remote volcano, and on 9 November 2004,
installation of the additional short-period seismic station LAV3, ~2 km
from the crater's vent.
Figure 11. Seismicity (number of earthquakes) versus time registered at
Reventador (station CONE) during mid-February 2003 through mid-December
2004. Anomalously elevated seismicity consisting mainly of volcano-tectonic
began in August 2004. Activity increased on 4 November 2004 and included
hybrid events. Previously unseen emergent, extended-duration, broad-band
earthquakes began on 22 November 2004. Courtesy of IG.
A helicopter overflight by IG-EPN staff on 10 November 2004 confirmed the
presence of a small lava dome, which appeared then to be confined to the
crater floor. This feature was not present on photos taken during an IG
overflight on 19 October 2004. During the 10 November overflight, a
continuous 2.5 km-high gas column escaped from the crater, accompanied by
sulfurous odors detected by personnel in the helicopter.
The date when lava began escaping the crater was not precisely known, but
it was thought to have been around 22 November, coincident with the
emergence of distinct seismic signals not previously observed at Reventador
(figure 11). The signals occurred in swarms and consisted of low-frequency
(1-10 Hz) waves of relatively low-amplitude. Their seismic records were
emergent (i.e. growing in amplitude with time) and of long duration (up to
60 seconds). They are thought to have been possibly associated with rock
falls from lava flowing down the cone's southern flank. As many as 200 of
these events were recorded each day at station CONE.
A return visit to the crater rim on 28 November (this time on foot)
documented abundant fresh lava in the crater (figure 12), a dramatic
increase in the volume of lava there. At least 0.5 x 10^6 m^3 of new lava
then covered the entire crater floor and appeared to be already flowing out
of the southern breach and into the surrounding caldera. Because of cloudy
weather, the exact extent of the flow remained indeterminate. The surface
of this lava flow also extended to the N and reached a level ~20 m below
the northern breach. Continuous lava extrusion or flowing or both were
heard within the crater, making sounds akin to glass breaking, and vigorous
roaring gas emissions originated from the crater's western margin. These
gas emissions and other smaller fumaroles contributed to a plume that was
continuously present, extending at least 1 km above the vent.
Figure 12. Reventador's 2004 lava flow/dome as seen on 28 November 2004.
The photo was taken looking W and downward from the cone's eastern crater
rim (see vantage point indicated by the star on figure 11). Courtesy of IG.
IG observers estimated that the total mid-December lava flow volume was ~3
x 10^6 m^3. The inferred 22 November date of flow onset would imply a
steady-state extrusion rate of ~0.1 x 10^6 m^3 per day and a flow front
advancing at ~80 m per day. These observations appear to conform with
satellite thermal infrared observations, which noted no significant
anomalies until the end of November, due presumably in large part to the
lava being confined within the steep-walled crater. Inclement weather
occurred and also may have impeded some of the satellite thermal observations.
The most recent visit to the crater rim, on 11 December 2004, traced the
source of degassing and lava outflow to the most elevated portion of a
small dome-like feature at the central western margin of the crater. Figure
13 shows how instrumentally aided nighttime incandescence observations
disclosed both the vent area and surficial flow-textures extending S
towards the southern breach of the cone. Figure 14 also documents a
comparatively narrow arm of lava trending towards the cone's northern
breach. Nighttime incandescence from the lava flow was also visible from
local communities such as El Chaco, ~20 km distant.
Figure 13. Thermal image of the lava flow in the interior of Reventador
crater taken with a Forward Looking Infrared (FLIR) imager at 2000 on 11
December 2004. Courtesy of IG.
Figure 14 illustrates the scene on 12 December 2004 during a visit to the
front of the most advanced lobe of lava (for location, see star at end of
flow lobe, figure 9). IG-EPN staff estimated the flow front at ~20 m high
and saw incandescent blocks falling off of it.
Figure 14. A N-looking view of Reventador's gray-colored lava-flow front
taken on 12 December 2004 at ~ 2,600 m elevation. Person at right indicates
scale of the advancing flow front. The lava flow emanated from the breach
in the S side of the cone's crater, a spot seen in the photo's upper left.
Courtesy of IG.
Background. Reventador is the most frequently active of a chain of
Ecuadorian volcanoes in the Cordillera Real, well E of the principal
volcanic axis. The forested dominantly andesitic stratovolcano rises to
3,562 m above the remote jungles of the western Amazon basin. A 4-km-wide
caldera widely breached to the E was formed by edifice collapse and is
partially filled by a young, unvegetated stratovolcano that rises about
1,300 m above the caldera floor to a height above the caldera rim.
Reventador has been the source of numerous lava flows as well as explosive
eruptions that were visible from Quito in historical time. Frequent lahars
in this region of heavy rainfall have constructed a debris plain on the
eastern floor of the caldera. The largest historical eruption at Reventador
took place in 2002, producing a 17-km-high eruption column, pyroclastic
flows that traveled up to 8 km, and lava flows from summit and flank vents.
Information Contacts: Patricio Ramon, Daniel Andrade, David Rivero,
Alexandra Alvarado, Sandro Vaca, and Pete Hall, Geophysical Institute (IG),
Escuela Politecnica Nacional, Apartado 17-01-2759, Quito, Ecuador (URL:
www.igepn.edu.ec/; Email: pramon@igepn.edu.ec;
dandrade@igepn.edu.ec; mhall@igepn.edu.ec); Jeffrey B. Johnson, Dept. of
Earth Sciences, James Hall University of New Hampshire, Durham, NH 03824
(jeff.johnson@unh.edu); MODIS Thermal Alert System, Hawaii Institute of
Geophysics and Planetology (HIGP), School of Ocean and Earth Science and
Technology, University of Hawaii at Manoa (URL:
www.modis.higp.hawaii.edu).
Fuego
Guatemala
14.47°N, 90.88°W; summit elev. 3,763 m
All times are local (= UTC - 6 hours)
Explosions and lava flows at Fuego continued after October 2003 (Bulletin
v. 28, no. 10). Similar activity prevailed through 2003 and 2004. This
report discusses events during November-December 2003 and includes a table
summarizing Fuego's 2003 behavior (table 3). A future report will discuss
2004 activity and will include a map showing critical place names. Several
pyroclastic flows occurred in 2003.
Table 3. Representative examples of reported volcanism at Fuego during
2003. Courtesy of INSIVUMEH.
Date - Lava flows, incandescent avalanches, and
pyroclasticflows (PFs)
- Ash column and ash fall
- Data source(s)
08 Jan 2003 - Lava flows. Two PFs (down Sta. Teresa drainage).
- Steam-and-ash to ~ 5.7 km a.s.l., drifted W.
- INSIVUMEH, CONRED, Washington VAAC, EFE via COMTEX,
Prensa Libra
Mid Jan 2003 - Incandescent avalanches down flanking canyons.
- ~ 2 km above summit, drifting S and SW, depositing
fine ash.
- INSIVUMEH, Washington VAAC
28 Apr-01 May - Incandescent avalanches.
- Intermittent ash eruptions, One ash plume reached ~
7 km a.s.l., blown SW
at 20-30 km/hour; some puffs visible over the coast.
- INSIVUMEH, Washington VAAC; US Air Force Weather Agency
29 Jun 2003 - Lava flows and avalanches down E flank
(incandescence seen from city of
Antigua and the coast). PFs extended ~ 1.5 km down
the W flank.
- Ash fell in villages to W and SE; Ash clouds to ~ 900 m.
- INSIVUMEH
09 Jul 2003 - Lava dome collapse PFs.
- Strong explosions sent ash to ~ 2 km above summit;
ash fell to W and SE
of summit.
- Washington VAAC, Prensa Libre
07 Aug 2003 - N/A
- A small ash emission seen on satellite imagery. The
ash cloud drifted NW
and covered an area about 3.5 by 3.5 km.
- Washington VAAC
08 Sep 2003 - N/A
- Ash plumes; one drifted S and covered an area of 5 x
5 km; another rose
to ~ 6 km a.s.l.
- Washington VAAC
09 Oct 2003 - N/A
- A pilot saw Fuego ash reaching ~ 4.6 a.s.l. No ash
was visible on
satellite imagery.
- Washington VAAC
17 Oct 2003 - Small incandescent avalanche down the Sta. Teresa
valley.
- A 33-minute-long eruption sent a gas-and-ash plume
to ~ 1.5 km above
the crater.
- INSIVUMEH
Nov-Dec 2003 - Incandescent avalanches.
- 4 November explosions threw material 150 m above
crater rim; 18-19
November, gas-and-ash plumes up to 1.2 km above the
crater; 28 Nov-1 Dec,
700-900 m above the crater; 7-9 December, 500 m
above crater; 10-16
December, 200-1000 m above the crater, and 18-22 and
30 December,
'low-level plumes.'
- INSIVUMEH
Tremor was common and at times abundant during 2003, including in the last
two months of the year. On 21 November, almost continuous harmonic tremor
was detected for a span of 21 hours. On 23 November intervals of tremor
lasted between 0.5 and 3 hours.
The Washington VAAC archive contains 48 ash advisories on Fuego. The number
of these advisories were as follows, during the stated months of 2003: 14
advisories in January (on the 8th, 9th, 11th, 12th, and 20th); 11 in April
(on the 17th, 28th, 29th, and 30th); eight in May (1st and 2nd); three in
June (30th), six in July (1st, 9th, and 10th), two in August (7th), two in
September (29th); and two in October (9th). The most impressive plumes
depicted in satellite-based graphics were for 28 April-1 May 2003, when
they often stretched well out to sea, reaching ~160 km SW from Fuego.
Otherwise, the graphics generally depicted much smaller plumes, in some
cases very local ones. The graphic for 28 September showed small plumes
from Fuego as well as simultaneous ones from Pacaya and Santa Maria.
Background. Volcan Fuego, one of Central America's most active volcanoes,
is one of three large stratovolcanoes overlooking Guatemala's former
capital, Antigua. The scarp of an older edifice, Meseta, lies between
3,763-m-high Fuego and its twin volcano to the N, Acatenango. Collapse of
the ancestral Meseta volcano about 8,500 years ago produced the massive
Escuintla debris-avalanche deposit, which extends about 50 km onto the
Pacific coastal plain. Growth of the modern Fuego volcano followed,
continuing the southward migration of volcanism that began at Acatenango.
In contrast to the mostly andesitic Acatenango volcano, eruptions at Fuego
have become more mafic with time, and most historical activity has produced
basaltic rocks. Frequent vigorous historical eruptions have been recorded
at Fuego since the onset of the Spanish era in 1524, and have produced
major ashfalls, along with occasional pyroclastic flows and lava flows.
Information Contacts: Instituto Nacional de Sismologia, Vulcanologia,
Meteorologia e Hidrologia (INSIVUMEH), Unit of Volcanology, Geologic
Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala
City, Guatemala (URL: www.insivumeh.gob.gt/); Washington Volcanic
Ash Advisory Center (VAAC), Satellite Analysis Branch, NOAA/NESDIS E/SP23,
NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746 USA
(URL: www.ssd.noaa.gov/); Charles R. Holliday, Air Force Weather
Agency, Offutt Air Force Base, Nebraska 68113 USA; Prensa Libre
(newspaper), 13 calle 9-31 zona 1, 01001 Guatemala City, Guatemala (URL:
www.prensalibre.com/).
__________________________________________________________
Global Volcanism Program, NHB E-421 Tel: (202) 633-1800
Smithsonian Institution Fax: (202) 357-2476
Washington, DC 20560-0119 Email: gvp@si.edu
Internet: www.volcano.si.edu/gvp/
posted by:
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Re: GVN Bulletin
Fri, February 11, 2005 - 5:52 AM********************************************************
Bulletin of the Global Volcanism Network, December 2004
********************************************************
From: Ed Venzke <venzke@volcano.si.edu>
Bulletin of the Global Volcanism Network
Volume 29, Number 12, December 2004
Piton de la Fournaise (Reunion Island) August-October eruption sends lava
flows to the sea; pillow lavas
Heard (Indian Ocean) Thermal alerts indicate crater lake activity starting
in June 2003 until June 2004
McDonald Islands (Indian Ocean) Thermal anomaly detected on 14 November 2004
Soputan (Indonesia) Explosive eruption causes ash plume and avalanche on 18
October 2004
Canlaon (Philippines) Alert level lowered after seismic decrease; January
2005 phreatic ash emission
Mayon (Philippines) Minor activity in June, July, and September 2004;
reported ash emission
Taal (Philippines) New episode of seismic unrest began in September 2004
Anatahan (Mariana Islands) New eruptive episode begins in January 2005; ash
plumes and dome growth
Villarrica (Chile) Active lava lake observed during late 2004
Deception Island (Antarctica) Annual investigations reveal continuing
seismicity and fumaroles
Editors: Rick Wunderman, Edward Venzke, and Gari Mayberry
Volunteer Staff: Robert Andrews, Jacquelyn Gluck, William Henoch, and
Catherine Galley
Piton de la Fournaise
Reunion Island, Indian Ocean
21.229°S, 55.713°E; summit elev. 2,631 m
All times are local (= UTC + 4 hours)
Inflation over the last year and a half, monitored by permanent GPS
stations, has not been interrupted by six eruptions over this period, the
latest during 2-18 May 2004 (Bulletin v. 29, no. 5). Increased seismicity
and ground deformation reported by the Observatoire Volcanologique du Piton
de la Fournaise (OVPDLF) in late June 2004 continued through 9 August when
the seismic network recorded 50-70 low-intensity earthquakes. The third
eruption of 2004 started on 13 August. Increasing seismicity and fissure
opening had occurred since early July 2004. At 0240 in the morning of 13
August, a 25-minute seismic crisis beneath the summit preceded the opening
of an ~500-m-long E-W fissure within Dolomieu crater, with the fissure
continuing on the E flank to an elevation of 1,900 m. The main activity was
located at 2,150 m elevation. A significant lava flow ran down the "Grandes
Pentes."
Ten days after the beginning of the eruption, ~750 m of National Road 2 was
overrun, and on 25 August lava from an 8.5-km-long system of lava tubes
entered the sea. A 670-m-long, 320-m-wide platform was build up within
several days, representing more than 2 x 10^6 m^3 of material. A second
smaller platform was build up in the following days by nearby lava flows
entering the sea. Two small hornitos, up to 8 m high, formed on the seaside
edge of the first platform. The main eruption phase stopped on 2 September.
However, significant phreatic activity continued on the new platform and
was followed by two minor phases from the main vent on the E flank, the
last one stopping at about 0300 on 4 October. Formation of pillow lava was
recorded by professional divers for the first time at ile de la Reunion, at
a water depth of 50 m in front of the new platform.
The Toulouse Volcanic Ash Advisory Center reported noteworthy eruptive
activity beginning on 4 September, following the end of the main eruption
phase. Ash reportedly fell near the volcano's summit, and a lava flow
entering the sea produced a steam and ash plume that rose ~2 km. Emissions
ceased on the morning of 7 September.
Background. The massive Piton de la Fournaise basaltic shield volcano on
the French island of Reunion in the western Indian Ocean is one of the
world's most active volcanoes. Much of its >530,000 year history overlapped
with eruptions of the deeply dissected Piton des Neiges shield volcano to
the NW. Three calderas formed at about 250,000, 65,000, and less than 5,000
years ago by progressive eastward slumping of the volcano. Numerous
pyroclastic cones dot the floor of the calderas and their outer flanks.
Most historical eruptions have originated from the summit and flanks of
Dolomieu, a 400-m-high lava shield that has grown within the youngest
caldera, which is 8 km wide and breached to below sea level on the eastern
side. More than 150 eruptions, most of which have produced fluid basaltic
lava flows, have occurred since the 17th century. Only six eruptions, in
1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on
the outer flanks of the caldera. The Piton de la Fournaise Volcano
Observatory, one of several operated by the Institut de Physique du Globe
de Paris, monitors this volcano.
Information Contacts: Thomas Staudacher, Observatoire Volcanologique du
Piton de la Fournaise Institut de Physique du Globe de Paris, 97418 La
Plaine des Cafres, La Reunion, France (URL:
volcano.ipgp.jussieu.fr:8080/reu...tml; Email:
Thomas.Staudacher@univ-reunion.fr); Toulouse Volcanic Ash Advisory Center
(VAAC), Meteo-France, 42 Avenue G. Coriolis, 31057 Toulouse Cedex, France
(Email: vaac@meteo.fr; URL:
www.meteo.fr/aeroweb/inf...index.html).
Heard
southern Indian Ocean
53.106°S, 73.513°E; summit elev. 2,745 m
Infrared satellite data triggered MODVOLC thermal alerts between 24 May
2000 and 2 February 2001 (Bulletin v. 28, no. 1). A new series of alerts
began on 9 June 2003, with frequent alerts continuing until 14 June 2004.
The cloud-free ASTER imagery from June 2003 to June 2004 was examined, and
although it does not offer very complete coverage of this new phase of
activity, all the images contained very small anomalies (just a few pixels)
in the central crater. This suggests that most of these alerts are due to
increased activity at the lava lake, with no indication of lava flows.
Also, all the 2003-2004 MODVOLC anomalies were 1-2 pixels (no elongate
thermal anomalies), further suggesting that this is local central-vent
activity.
Background. Heard Island on the Kerguelen Plateau in the southern Indian
Ocean consists primarily of the emergent portion of two volcanic
structures. The large glacier-covered composite basaltic-to-trachytic cone
of Big Ben comprises most of the island, and the smaller Mt. Dixon volcano
lies at the NW tip of the island across a narrow isthmus. Little is known
about the structure of Big Ben volcano because of its extensive ice cover.
The historically active Mawson Peak forms the island's 2745-m high point
and lies within a 5-6 km wide caldera breached to the SW side of Big Ben.
Small satellitic scoria cones are mostly located on the northern coast.
Several subglacial eruptions have been reported in historical time at this
isolated volcano, but observations are infrequent and additional activity
may have occurred.
Information Contacts: Matt Patrick, Luke Flynn, Harold Garbeil, Andy
Harris, Eric Pilger, Glyn Williams-Jones, and Rob Wright, HIGP Thermal
Alerts Team, Hawai'i Institute of Geophysics and Planetology (HIGP) /
School of Ocean and Earth Science and Technology (SOEST), University of
Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA
(hotspot.higp.hawaii.edu/, Email: patrick@higp.hawaii.edu).
McDonald Islands
southern Indian Ocean
53.03°S, 72.60°E; summit elev. 186 m
The first ever MODVOLC thermal anomaly at the McDonald Island volcano was
detected on 14 November 2004. The anomaly, one pixel in size, was located
directly over the island. There have been none since then through 13
January 2005, nor have there been any other obvious false-alert pixels in
the vicinity, suggesting that this anomaly was genuine.
Andrew Tupper investigated the above-mentioned anomaly (on a Terra MODIS
image, overpass time 1827 UTC, 14 November 2004; seen in bands 20-25
(3.8-4.5 um)). Basically, the anomaly occurred within 2 km of the location
of the summit coordinates given in the title above. Tupper went on to note:
"I've looked at other MODIS images from around that time, and some recent
AVHRR images, but it is extremely difficult to get a cloud-free shot of
that area. There are no other hot spots visible, and no volcanic plumes
visible, but unless there was a bonfire lit by a stranded party of
toothfish poachers at the time, I can't think of any reason to doubt that
the hot-spot is volcanic."
Background. Three small, low islands on the Kerguelen Plateau form the
McDonald Islands. The largest island, McDonald, is composed of a layered
phonolitic tuff plateau cut by phonolitic dikes and lava domes. A possible
nearby active submarine center was inferred from phonolitic pumice that
washed up on Heard Island in 1992. Volcanic plumes were observed in
December 1996 and January 1997 from McDonald Island. During March of 1997
the crew of a vessel that sailed near the island noted vigorous steaming
from a vent at the N side of the island along with possible pyroclastic
deposits and lava flows. During a visit to the area in November 2002 the
island was reported to have more than doubled in area since previous
reported observations in November 2000. The high point of the island group
had shifted to the N end of MacDonald island, which had merged with Flat
Island to the north.
Information Contacts: Matt Patrick, Luke Flynn, Harold Garbeil, Andy
Harris, Eric Pilger, Glyn Williams-Jones, and Rob Wright, HIGP Thermal
Alerts Team, Hawai'i Institute of Geophysics and Planetology (HIGP) /
School of Ocean and Earth Science and Technology (SOEST), University of
Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA
(hotspot.higp.hawaii.edu/, Email: patrick@higp.hawaii.edu); Andrew
Tupper, Darwin Volcanic Ash Advisory Centre (VAAC), Commonwealth Bureau of
Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina,
NT 0811, Australia (URL: www.bom. gov.au/info/vaac/; Email:
darwin.vaac@bom.gov.au).
Soputan
Sulawesi, Indonesia
1.108°N,124.725°E; summit elev. 1,784 m
All times are local (= UTC + 8 hours)
Activity at Soputan that began on 18 July 2003 (Bulletin v. 28, no. 8)
continued with occasional ash explosions in August (Bulletin v. 28, nos.
10-11) and through 4 September 2003 (Bulletin v. 29, no. 11). The report of
the 12 December 2004 eruption (Bulletin v. 29, no. 11) also mentioned
activity on 18 October. The following information from the Indonesian
Directorate of Volcanology and Geological Hazard Mitigation describes that
October 2004 activity in greater detail.
Volcanic tremor increased at 0930 on 18 October 2004 with amplitudes in the
range of 10-40 mm. From 1026 to 1452 tremor amplitudes reached a maximum of
41 mm (over scale). At 1041 Soputan exploded, releasing a white to gray ash
column as high as 600 m above the crater rim and drifting E. The explosion,
along with rumbling sounds, was heard at the Post Observatory ~12 km from
the summit. Based on increasing seismicity, the official hazard level was
raised to Orange or II (on a scale of I-IV) at 1500 that day. At 1815
incandescence was visible, rising 25-30 m above the crater rim. Ash reached
the Observatory at 2130, and a "lava avalanche" at 2135 traveled to the S.
Tremor was recorded until 0712 on the following day, 19 October, with
amplitudes of 0.5-2 mm.
A GOES-9 satellite loop of the 18 October 2004 eruption was compiled by the
Darwin Volcanic Ash Advisory Centre (VAAC). Based on the dispersion
patterns and infrared temperatures (minimum temperature of zero degrees),
the cloud probably reached between 5,000 and 6,000 m altitude, where there
was an atmospheric inversion that prevented further rise.
The Darwin VAAC also noted that a satellite image from the Terra MODIS
instrument taken at 0210 UTC on 1 September 2003 showed an eruption plume
during clear weather. The imaged eruption, described as a low-level cloud
streaming to the SW that probably didn't rise much above the summit,
occurred during a period of previously reported ash plumes and lava flow
activity (Bulletin v. 28, no. 10).
Background. The small Soputan stratovolcano on the southern rim of the
Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of
Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano
rises to 1784 m and is located SW of Sempu volcano. It was constructed at
the southern end of a SSW-NNE trending line of vents. During historical
time the locus of eruptions has included both the summit crater and
Aeseput, a prominent NE-flank vent that formed in 1906 and was the source
of intermittent major lava flows until 1924.
Information Contacts: Directorate of Volcanology and Geological Hazard
Mitigation, Jalan Diponegoro 57, Bandung 40122, Indonesia (Email:
dali@vsi.dpe.go.id; URL: www.vsi.esdm.go.id/); Andrew Tupper, Darwin
Volcanic Ash Advisory Centre (VAAC), Australian Bureau of Meteorology (URL:
www.bom.gov.au/info/vaac/soputan.shtml).
Canlaon
central Philippines
10.412°N, 123.132°E; summit elev. 2,435 m
The Philippine Institute of Volcanology and Seismology (PHIVOLCS) noted in
a March 2004 report that the most recent eruptive episode of Canlaon had
begun on 7 March 2003. Their 2003 Annual Report described a mild
ash-and-steam emission on 7 March that rose 1 km above the summit and
resulted in traces of ash deposited at Cabagnaan, 5.5 km S. On 17 March
2003 the hazard status had been raised to Alert Level 1 (Bulletin v. 28,
nos. 3, 6, 7, and 8). A total of 46 minor ash ejections were documented or
observed, most from June to July 2003, characterized by steam clouds with
minor ash that rose as high as 1,500 m. Prevailing winds dispersed the ash
over the mid-upper slopes in the SW and SE sectors of the volcano.
Sporadic recordings of high-frequency volcanic earthquakes (HFVQ) and
low-frequency volcanic earthquake swarms (LFVQ) starting in January 2003
prompted PHIVOLCS to issue a warning on the possibility of sudden phreatic
explosions. In June 2003 daily occurrences of LFVQs increased dramatically
and these heightened levels were sustained until July 2003. Low-frequency
short-duration harmonic tremors (SDHLF) also appeared in June 2003 and
increased like the LFVQs, indicating a continuous supply and transport of
volcanic fluids towards the shallow levels of the crater area.
A general trend towards volcanic quiet was recognized during August 2003,
but the status was maintained at Alert Level 1 because HFVQs, LFVQs, and
SDHLFs persisted, though in diminishing numbers, until September 2003.
After that time, steam emissions from the summit crater were only weak or
absent, with normal levels of seismic activity. On 1 March 2004 PHIVOLCS
lowered the hazard status to Alert Level 0, meaning the volcano has
returned to a quiet state. The public was strongly advised, however, to
consider the risk when entering the 4-km Permanent Danger Zone because
sudden phreatic explosions may occur without warning. People planning to
climb the volcano are advised to check with an observatory first.
Phreatic emission, January 2005. The value of continued warnings was shown
on 21 January 2005, when Canlaon generated a sudden brief ash emission. The
PHIVOLCS observatory at La Carlota City College reported moderate emission
of a grayish volcanic plume at about 0930 that rose to ~500 m above the
active crater and drifted WNW and SW, depositing light ash on the upper SW
slopes. Traces of ash deposits were also observed at Cabagnaan, 5.5 km SW
of the active crater. No coincident volcanic earthquakes were recorded, and
Canlaon continued to be seismically quiet. These observations suggest the
activity is hydrothermal in nature and occurring at very shallow levels
near the crater floor.
Background. Canlaon volcano (also spelled Kanlaon), the most active of the
central Philippines, forms the highest point on the island of Negros. The
massive 2435-m-high stratovolcano is dotted with fissure-controlled
pyroclastic cones and craters, many of which are filled by lakes. The
summit of Canlaon contains a broad elongated northern caldera with a crater
lake and a smaller, but higher, historically active crater to the south.
The largest debris avalanche known in the Philippines traveled 33 km to the
SW from Canlaon. Historical eruptions, recorded since 1866, have typically
consisted of phreatic explosions of small-to-moderate size that produce
minor ashfalls near the volcano.
Information Contact: Philippine Institute of Volcanology and Seismology
(PHIVOLCS), Department of Science and Technology, PHIVOLCS Building, C.P.
Garcia Avenue, Univ. of the Philippines Campus, Diliman, Quezon City,
Philippines (URL: www.phivolcs.dost.gov.ph/).
Mayon
Luzon, Philippines
13.257°N, 123.685°E; summit elev. 2,462 m
An explosion-type volcanic earthquake detected by the Upper Anoling seismic
station on the afternoon of 3 June 2004 was not visually observed due to
thick clouds covering the summit. Residents closer to the Upper Anoling
Seismic Station and Mayon Resthouse did not notice any unusual activity. No
traces of ash or changes in the crater wall were observed. Sulfur dioxide
(SO2) emission rose from 1,169 metric tons/day (t/d) on 12 May to 2,521 t/d
on 4 June, then decreased to 1,514 t/d on 18 June. Precise leveling
measurements showed a slight but deflation of the edifice. The number of
low-frequency volcanic earthquakes and low-frequency short-duration
harmonic tremors increased in June to almost twice the number recorded in
May. In addition, faint crater glow continued to be observed at the summit,
as it had since 7 October 2003.
Another explosion was recorded on 22 July 2004. According to news reports,
ash from that event was deposited in two local villages.
Sulfur dioxide (SO2) emissions remained only slightly above baseline at
829 metric tons per day as of 6 September 2004. On the evening of 12
September 2004 the very faint glow at the summit of Mayon intensified
slightly. The brighter incandescence, observable from Lignon Hill Volcano
Observatory and in Legaspi City proper, coincided with a slight increase in
the overall background tremor detected by seismographs around the volcano.
However, there were no significant changes in ground deformation or SO2
measurements. A news report also noted that volcanic material emitted from
the crater that day set fire to grass on the volcano's slopes.
The hazard status remained at Alert Level 2, indicating a low level of
volcanism. PHIVOLCS reminded the public to refrain from venturing into the
6-km Permanent Danger Zone because life-threatening volcanic flows may
occur with little or no warning.
Background. Beautifully symmetrical Mayon volcano, which rises to 2462 m
above the Albay Gulf, is the Philippines' most active volcano. The
structurally simple volcano has steep upper slopes averaging 35-40 degrees
that are capped by a small summit crater. The historical eruptions of this
basaltic-andesitic volcano date back to 1616 and range from strombolian to
basaltic plinian, with cyclical activity beginning with basaltic eruptions,
followed by longer term andesitic lava flows. Eruptions occur predominately
from the central conduit and have also produced lava flows that travel far
down the flanks. Pyroclastic flows and mudflows have commonly swept down
many of the approximately 40 ravines that radiate from the summit and have
often devastated populated lowland areas. Mayon's most violent eruption, in
1814, killed more than 1200 people and devastated several towns.
Information Contact: Philippine Institute of Volcanology and Seismology
(PHIVOLCS), Department of Science and Technology, PHIVOLCS Building, C.P.
Garcia Avenue, Univ. of the Philippines Campus, Diliman, Quezon City,
Philippines (URL: www.phivolcs.dost.gov.ph/); Associated Press (URL:
www.ap.org/); The Australian (www.theaustralian.news.com.au/).
Taal
Luzon, Philippines
14.002°N, 120.993°E; summit elev. 400 m
The Taal seismic monitoring network began to record significant volcanic
earthquakes on 23 September 2004. In general, the numbers of these events
occurring through 29 October increased, with a maximum 13 earthquakes on 15
October. Some of these earthquakes were instrumentally recorded with
relatively large amplitudes although none were felt by residents on Volcano
Island. Initial earthquake locations showed epicenters dispersed in the
vicinity of Main Crater, to the NNW near Binintiang Malaki, and to the SSE
near Calauit. Surface observations, however, did not indicate any
significant change in the thermal and steam emission characteristics of the
Main Crater lake area. The increased seismicity is an indication of a
low-level episode of unrest, although at this time there is no clear
indication of an impending eruption. A series of volcanic earthquakes was
recorded on 9 January 2005. Two of these earthquakes, only one minute
apart, were felt in Pira-piraso.
PHIVOLCS raised the hazard status on 29 October from Alert Level 0 to Alert
Level 1, meaning that there was a slight increase in seismic activity but
no eruption is imminent. PHIVOLCS recommend as off-limits the Main Crater
area because sudden steam explosions may occur or high concentrations of
noxious gases may accumulate. Several fissures traversing the Daang Kastila
Trail are also potentially hazardous as possible sites of future steam
emission. PHIVOLCS is conducting several enhancements of the monitoring
system at Taal with deployment of more seismometers and ground-deformation
surveillance equipment. The entire Volcano Island is a Permanent Danger
Zone and permanent settlement is strictly prohibited.
Background. Taal volcano is one of the most active volcanoes in the
Philippines and has produced some of its most powerful historical
eruptions. In contrast to Mayon volcano, Taal is not topographically
prominent, but its prehistorical eruptions have greatly changed the
topography of SW Luzon. The 15 x 20 km Taal caldera is largely filled by
Lake Taal, whose 267 sq km surface lies 700 m below the south caldera rim
and only 3 m above sea level. The maximum depth of the lake is 160 m, and
several eruptive centers lie submerged beneath the lake. The 5-km-wide
Volcano Island in north-central Lake Taal is the location of all historical
eruptions. The island is a complex volcano composed of coalescing small
stratovolcanoes, tuff rings, and scoria cones that has grown about 25% in
area during historical time. Powerful pyroclastic flows and surges from
historical eruptions of Taal have caused many fatalities.
Information Contact: Philippine Institute of Volcanology and Seismology
(PHIVOLCS), Department of Science and Technology, PHIVOLCS Building, C.P.
Garcia Avenue, Univ. of the Philippines Campus, Diliman, Quezon City,
Philippines (URL: www.phivolcs.dost.gov.ph/).
Anatahan
Mariana Islands, central Pacific Ocean
16.35°N, 145.67°E; summit elev. 788 m
All times are local (= UTC + 10 hours)
Although the latest eruptive period ended in late July (Bulletin v. 29, no.
8), the volcanic system at Anatahan continued to exhibit unrest in the
following months. On 27 September, several hours after the onset of a
series of intense tropical depressions and storms, the first long-period
seismic events since July 2004 were recorded. However, only a few, small
events occurred. Beginning on 12 October, several episodes of small,
regularly-spaced long-period events were recorded at intervals of 4-15
seconds. On 18 October, people in Saipan smelled H2S during very hazy
visibility, but no plume was detected on satellite imagery by the
Washington Volcanic Ash Advisory Center (VAAC).
Based on a pilot report to the Guam Forecast Office, the Washington VAAC
reported that ash from Anatahan was at a height of ~3 km altitude on 2
December. Ash was not visible on satellite imagery, but a hotspot was
briefly evident on infrared imagery.
Eruptions in January 2005. Major eruptive activity at Anatahan resumed on 5
January 2005, preceded by two days of small long-period earthquakes and a
day of harmonic tremor. The airport tower at Guam confirmed that a plume of
diffuse ash and gas up to ~200 m above the vent was visible at first light
on 6 January, and at the 1225 hours VAAC reported a plume 60 km long and 20
km wide, blowing W.
Frequent Strombolian explosion signals began on 6 January and continued
during 7 and 8 January, accompanied by a change in the seismic signals,
from harmonic tremor to a broader band tremor, with explosions recorded by
microphones several times per minute. The eruption type and activity level
were both very similar to the peak eruptive activity during the eruption of
April-June 2004 (Bulletin v. 29, nos. 4, 5, and 6). During an overflight on
7 January, personnel from the Emergency Management Office (EMO) reported
ash rising well above 1,500 m and a plume that likely extended up to 100 km
downwind. A dome was visible in the crater and bombs were observed rising
less than 600 m.
On 7 January ash rose to ~3 km and bombs a meter or more in diameter were
expelled to ~100 m and formed a new cinder cone ~120 m in diameter. The
amplitude of the explosion signals increased slowly after 6 January to
about double these values by noon on 10 January, with explosions every 3-10
seconds. Explosion signals amplitudes then plunged suddenly to half the
values at the start of 10 January. The amplitudes surged again, nearly
doubling by approximately 0400 on 11 January, dropping to half the value
again by about noon. The eruption apparently stabilized at that level
through 14 January. During 15-19 January, the eruption appears to have
stopped twice for a few hours but swiftly resumed at higher levels.
National Oceanic and Atmospheric Agency (NOAA) satellite photos show a
plume of vog (volcanic smog) trailing ~60 km downwind.
Near mid-day on 20 January seismicity dropped abruptly to near background
levels, whereas microphone noise became fairly continuous, indicating that
the explosions had ceased but that degassing may have been continuing. The
apparent cessation of Strombolian activity lasted until late 22 January,
when explosions resumed. The eruption peaked about 0700 on 23 January, at
which time a SIGMET (significant meteorological forecast) was issued by the
FSS (Flight Service Station) Honolulu, based on pilot reports of ash up to
3-4.6 m. The explosions then decreased somewhat but were still frequent and
strong through 24 January, based on the seismicity.
The EMO placed Anatahan Island off limits until further notice and
concluded that, although the volcano was not currently dangerous to most
aircraft within the CNMI airspace, conditions may change rapidly. Aircraft
should pass upwind of, or beyond 30 km downwind from, the island, and
exercise due caution within 30 km of Anatahan.
Synopsis of recent eruptions. Anatahan had no historical eruptions prior to
2003. On 10 May of that year, after several hours of increasing seismicity,
a phreatomagmatic eruption sent ash to over 10 km and deposited about 10
million cubic meters of material over the island and sea. A very small
craggy dome extruded during late May and was destroyed during explosions on
14 June, after which the eruption essentially ceased. A second eruption
began about 9 April 2004, after more than a week of increasing seismicity.
The eruption consisted of passive extrusion during mid-April, then
increased to Strombolian explosions every minute or two on 24 April. The
Strombolian explosions continued through mid-July, often sending a thin
plume of gas and ash upwards a few hundreds of meters and 100 km downwind.
Activity decreased substantially on 26 July, though visitors to the island
three months later could still see very small amounts of steam and ash
rising 30-40 m above the crater rim and could smell SO2 near the crater.
Background. The elongated, 9-km-long island of Anatahan in the central
Mariana Islands consists of two coalescing volcanoes with a 2.3 x 5 km,
E-W-trending summit depression formed by overlapping summit calderas. The
larger western caldera is 2.3 x 3 km wide and extends eastward from the
summit of the western volcano, the island's 788-m high point. Ponded lava
flows overlain by pyroclastic deposits fill the caldera floor, whose SW
side is cut by a fresh-looking smaller crater. The summit of the lower
eastern cone is cut by a 2-km-wide caldera with a steep-walled inner crater
whose floor is only 68 m above sea level. Sparseness of vegetation on the
most recent lava flows on Anatahan indicated that they were of Holocene
age, but the first historical eruption of Anatahan did not occur until May
2003, when a large explosive eruption took place forming a new crater
inside the eastern caldera.
Information Contacts: Juan Takai Camacho and Ramon Chong, Emergency
Management Office of the Commonwealth of the Northern Mariana Islands
(CNMI/EMO), P.O. Box 100007, Saipan, MP 96950, USA (URL:
www.cnmiemo.org/; Email: juantcamacho@hotmail.com and
rcchongemo@hotmail.com); Frank Trusdell, Hawaii Volcano Observatory, U.S.
Geological Survey (HVO/USGS), Hawaii National Park, HI 96718, USA (URL:
hvo.wr.usgs.gov/cnmi/; Email: trusdell@usgs.gov); Washington
Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch, NOAA/NESDIS
E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD
20746 USA (URL: www.ssd.noaa.gov/); NOAA/ National Weather Service,
National Centers for Environmental Prediction, Aviation Weather Center,
Volcanic Ash SIGMETS, (URL:adds.aviationweather.gov/airmets/)
Villarrica
central Chile
39.42°S, 71.93°W; summit elev. 2,847 m
All times are local (= UTC - 4 hours, -3 hours October-March)
The last report of activity at Villarrica, through May 2002 (Bulletin v.
27, no. 6), described a general decrease in incandescence in the summit
crater's lava lake, and noted ballistics ejected in January 2002.
Jacques-Marie Bardintzeff reported that climbers to the top of the volcano
on 5 November 2004 noted a strong sulfur smell and observed projections of
red lava at a depth of 200-300 m in the crater. On 16 November, a small
lava lake was visible in the crater from the air; it was photographed on
the 19th (figure 1). Many volcanologists attending the IAVCEI General
Assembly at Pucon 14-19 November 2004 ascended and observed activity in the
summit crater (figure 2). Although the lava lake itself lay at the bottom
of a steep-walled inner crater and was not visible, periodic ejection of
large quantities of incandescent lava fragments to a maximum height just
above the rim of the inner crater could be seen from a bench below the SW
rim of the outer summit crater (figure 3). Bardintzeff noted on 24 November
2004 that a white and blue plume of H2O vapor and SO2, extending to the E
from Villarrica, was observed from Pucon. During the night, the plume was
red colored. According to the local inhabitants, this was the first
observation of a plume since January 2004.
Figure 1. A near-vertical aerial view into the ~ 250-m-wide summit crater
of Villarrica volcano at about 1430 on 19 November shows the incandescent
lava lake in the steep-walled inner crater. The chain of dots left (north)
of the crater are climbers ascending to the crater rim. The photograph was
taken through the side window of a Cessna aircraft executing an extremely
sharp turn. Figure 2 (below) was taken from the upper left crater rim and
figure 3 from the lower right. Courtesy of Jean-Claude Tanguy.
Figure 2. Climbers walk along the outer snow-covered rim of Villarrica's
summit crater on 17 November 2004 and stand on a small bench just below the
SW rim (left), which provided periodic views of incandescent ejecta from
the inner crater lava lake (figure 3). Courtesy of Judy Harden.
Figure 3. Incandescent spatter and bombs are ejected from the lava lake in
the inner crater of Villarrica as seen from a bench just below the SW rim
of the outer crater on 17 November 2004. Courtesy of Judy Harden.
According to the Publicacion Oficial del Grupo Projecto de Observacion
Villarrica (P.O.V.I.) website, incandescence was seen above the summit
crater on the nights of 5-6 August and 27-28 October 2004 and frequently
during November and December. On the night of 12-13 December Strombolian
explosions every 2-5 minutes ejected incandescent spatter and bombs to 100
m height that landed on the outer crater rim. On the 13th the lava lake was
~30 m in diameter and at a depth of ~100 m. Vigorous convection of the lava
lake was punctuated at intervals not exceeding 15 seconds by Strombolian
explosions that ejected fine ash, lapilli up to 4 mm in diameter that fell
to within a few meters of the inner edge of the crater, and incandescent
spatter to the NE to heights of ~50 m. By 27 December solidification of
ejected spatter around the vent had decreased its diameter by 2/3 with
respect to 13 December, and Strombolian explosions at intervals of 2-5
minutes ejected material ~100 m above the vent. On 9 and 17 January minor
explosions took place at intervals of 1-2 minutes. By 17 January fissures
had formed around the N to E sides of the vent, and the opposite side of
the vent edge, and the slope above it, had collapsed.
Satellite-based MODIS thermal alerts were first detected at 0345 UTC on 5
November and also occurred on 6, 16, 17, 22, 24, and 29 November, 5, 8, 9,
14, 19, 21, and 31 December, and 1 and 2 January 2005. Prior to 5 November
2004, MODIS thermal alerts not previously reported in this Bulletin had
been detected at Villarrica on 23 May, 10 and 17 July, 2, 6, 25, and 27
August, 16 and 28 September, 2, 12, 14, 27, and 30 October, 1, 3, 22, and
28 November 2003, 31 January, 1-3, 7, 10, 12, and 14 February, and 0345 UTC
on 26 March 2004 (2345 local time 25 March). According to the P.O.V.I.
website, strong explosive activity ejected incandescent pyroclastic
material on 28 August 2003, and except for three cloud-covered days,
incandescence above the summit crater was seen daily from 27 January to 20
February 2004.
Background. Villarrica, one of Chile's most active volcanoes, rises above
the lake and town of the same name. It is the westernmost of three large
stratovolcanoes that trend perpendicular to the Andean chain. A 6-km wide
caldera formed during the late Pleistocene. A 2-km-wide caldera that formed
about 3,500 years ago is located at the base of the presently active,
dominantly basaltic to basaltic-andesitic cone at the NW margin of the
Pleistocene caldera. More than 30 scoria cones and fissure vents dot
Villarrica's flanks. Plinian eruptions and pyroclastic flows that have
extended up to 20 km from the volcano have been produced during the
Holocene. Lava flows up to 18 km long have issued from summit and flanks
vent. Historical eruptions, documented since 1558, have consisted largely
of mild-to-moderate explosive activity with occasional lava effusion.
Glaciers cover 40 km^2 of the volcano, and lahars have damaged towns on its
flanks.
General Reference. Calder, E.S., Harris, A.J.L., Pena, P., Pilger, E.,
Flynn, L.P., Fuentealba, G., and Moreno, H., 2004, Conbined thermal and
seismic analysis of the Villarrica volcano lava lake, Chile: Revista
Geologica de Chile, v. 31, no. 2, p. 259-272.
Lara, L.E., and Clavero, J. (eds.), 2004, Villarrica volcano (39.5°S),
Southern Andes, Chile: Servicio Nacional de Geologia y Mineria - Chile,
Santiago, Boletin No. 61.
Information Contacts: Jacques-Marie Bardintzeff, Laboratoire de
Petrographie- Volcanologie, Bât. 504 Universite Paris-Sud, F-91405 Orsay,
France (URL: www.lave-volcans.com/bardintzeff.html, Email:
bardizef@geol.u-psud.fr); Judy Harden, Department of Geology, University of
South Florida, 4202 E. Fowler Ave, SCA528, Tampa, FL 33620, USA (Email:
jaharden@juno.com); Publicacion Oficial del Grupo Projecto de Observacion
Villarrica - Internet (P.O.V.I.) (URL: www.povi.cl/); Jean-Claude
Tanguy, Univ. Paris 6 & Institut de Physique du Globe de Paris,
Observatoire de St. Maur, 94107 St. Maur des Fosses, France (Email:
tanguy@ipgp.jussieu.fr).
Deception Island
South Shetland Islands, Antarctica
62.97°S, 60.65°W; summit elev. 576 m
Deception Island is the most active volcano in the Antarctic Peninsula
region. A team of Spanish-Argentine scientists collected data from 25
November 2003 to 16 March 2004 in order to provide background activity
records. Local and regional seismicity, thermal activity, gas emission,
geodetic, and geological studies were carried out. During this survey, one
seismic antenna and three continuous-recording stations were installed
(figure 4). One dense seismic antenna with twelve vertical-component
short-period seismometers was located between the Spanish and Argentine
base stations, one vertical-component short-period seismometer was placed
at North Fumarole Bay (with telemetry), and three-component short-period
seismic stations were installed near both the "Gabriel de Castilla" Spanish
station and the Argentine station.
Figure 4. Seismological stations deployed at Deception Island in 2003-2004
summer survey. Courtesy of the Spanish-Argentine research team.
The recorded seismicity included long-period events (LP), volcanic-tremor
episodes (T), and a few volcano-tectonic earthquakes (VT). More than 3,660
LP events events were recorded (figure 5), 35 of them with hybrid
character, and many with frequencies of 1-8 Hz. Eight volcanic tremors
occurred with durations ranging from less than one hour to twenty-one
hours; 66 VT earthquakes were also recorded. Four remarkable periods of
activity were detected in this survey, during last December, mid-January,
early February, and mid-March. All of these periods were characterized by a
relatively high level of seismic activity with frequent LP events and
tremor. Most earthquakes recorded during the field season were located
inside the island, and these events have been closely related with LP and
tremor events. Earthquakes with S-P wave time lags of less than 3 seconds
were classified as local or VT, with local magnitudes of up to 2.0, none of
which were felt. LP seismicity might be related to thaw water (seasonal
effect) but this year's anomalous activity could also be due to strong
pressurization in a sealed system.
Figure 5. Long-period seismic activity at Deception Island during the
2003-2004 summer survey. Adapted from a histogram showing six types of
recorded seismicity. Courtesy of the Spanish-Argentine research team.
Fumarole temperatures and hot soils remained stable between 99 and 101ºC in
Fumarole Bay, 95ºC in Caliente hill, 65ºC in Whalers Bay, 41ºC in Telefon
Bay, and 72ºC in Pendulum Cove. Systematic monitoring of fumarolic activity
continued as in past years, and during this survey radon was measured.
Samples of condensable and uncondensable acid gases were collected. The
obtained composition from the fumarole vents at Fumarole Bay was similar to
previous years. The average chemical composition of the fumarolic gases was
H2O(v) (86.21%), CO2 (13.59%), H2S (0.19%), and SO2 (0.01%). Lapilli with a
coating of pyrite were found around vent outlets. Compositional changes in
acidic gases observed in early February and March 2004 correlated with
increased seismicity, especially with LP events.
Background. Ring-shaped Deception Island, one of Antarctica's most well
known volcanoes, contains a 7-km-wide caldera flooded by the sea. Deception
Island is located at the SW end of the Shetland Islands, NE of Graham Land
Peninsula, and was constructed along the axis of the Bransfield Rift
spreading center. A narrow passageway named Neptunes Bellows provides
entrance to a natural harbor that was utilized as an Antarctic whaling
station. Numerous vents located along ring fractures circling the low,
14-km-wide island have been active during historical time. Maars line the
shores of 190-m-deep Port Foster, the caldera bay. Among the largest of
these maars is 1-km-wide Whalers Bay, at the entrance to the harbor.
Eruptions from Deception Island during the past 8700 years have been dated
from ash layers in lake sediments on the Antarctic Peninsula and
neighboring islands.
Information Contacts: A.T.Caselli, C. Bengoa, and E. Rojas Vera,
Universidad de Buenos Aires-Instituto Antartico Argentino, Ciudad
Universitaria, Pab.2, (1428) Buenos Aires, Argentina (Email:
acaselli@gl.fcen.uba.ar); A. Bidone and G. Badi, Dpto. de Sismologia e
I.M., Facultad de Cs. Astronom. y Geofisicas, UNLP, Av. Centenario s/n
Paseo del Bosque, B1900FWA La Plata, Pcia. de Buenos Aires, Argentina;
Daria Zandomeneghi, Nieves Sanchez, Fermin Fernandez-Ibanez, and Jesus
Ibanez, Instituto Andaluz de Geofisica y P.D.S. Universidad de Granada,
Campus Universitario de Cartuja, s/n 18071, Granada, Spain.
__________________________________________________________
Global Volcanism Program, NHB E-421 Tel: (202) 633-1800
Smithsonian Institution Fax: (202) 357-2476
Washington, DC 20560-0119 Email: gvp@si.edu
Internet: www.volcano.si.edu/
-
Re: GVN Bulletin
Sat, March 12, 2005 - 9:21 AM*******************************************************
Bulletin of the Global Volcanism Network, January 2005
*******************************************************
From: Ed Venzke <venzke@volcano.si.edu>
Bulletin of the Global Volcanism Network
Volume 30, Number 1, January 2005
Asama (Japan) 1 September 2004 eruption followed by others at least as late
as 14 November
Raung (Indonesia) MODIS-MODVOLC infrared hot spots 3 June-8 Oct 2004;
aerial photos from 2001
Kerinci (Indonesia) 27 September 2004 ash plumes to 6 km altitude; thick
gray plumes during October 2004
Marapi (Indonesia) Small eruptions and seismicity during August to October 2004
Etna (Italy) 7 September eruption continues on W wall of Valle del Bove,
includes lava tubes, multiple vents
Erta Ale (Ethiopia) Hornitos on chilled lava lake surface in January 2005;
December 2004 glass analyses
Popocatepetl (Mexico) Relative quiet of 2004 ended during December 2004 and
January 2005
Colima (Mexico) Block-lava escapes starting in September 2004 getting well
down N flank by October
Editors: Rick Wunderman, Edward Venzke, and Gari Mayberry
Volunteer Staff: Robert Andrews, Jacquelyn Gluck, William Henoch, and
Catherine Galley
Asama
Honshu, Japan
36.40°N, 138.53°E; summit elev. 2,560 m
All times are local (= UTC + 9 hours)
At 2020 on 1 September 2004, an explosive eruption occurred from the summit
crater of Asama (Bulletin v. 29, nos. 8 and 10). As previously reported,
the resulting eruption cloud drifted NE, and ash fell ~250 km away. A
Reuters news report stated that this was its biggest eruption in 21 years
(since April 1983). A distinct plume was still discharging on 3 September,
when Asia Air Surveys took a vertical aerial photograph (figures 1 and 2).
Figure 1. Topographic map showing the flight lines and locations of aerial
photos at Asama volcano (N is towards the top), 3 September 2004. Courtesy
of Asia Air Survey Co., Ltd.
Figure 2. Aerial photo of Asama taken on 3 September 2004; the shot was
taken at the point labeled "90" on line C3 on figure 1, in effect, from a
point slightly E of the summit crater. Copyrighted photo is used here with
permission of Asia Air Survey Co., Ltd. (their photo number C3-9590).
Setsuya Nakada and Yukio Hayakawa informed Bulletin editors of Asama's
eruptions by preparing reports and outlines in English, or explaining the
significance of several kinds of data that were not otherwise accessible in
English. Investigators plan to present data on Asama's 2004 eruptions at
upcoming conferences, including The Joint Geoscience Meeting, to be held in
May 2005 at Makuhari, Chiba (Japan).
A small eruption around 1530 on 14 September (figure 3) produced an ash
plume that rose 1-2.5 km above the volcano. A smaller eruption earlier that
day around 0328 produced a plume that rose ~300 m. A small amount of ash
fell in Takasaki, ~45 km from the volcano.
Figure 3. A drifting eruption cloud emitted at Asama, as seen from the
Geological Society of Japan office building in Tsukuba, ~150 km E of the
volcano. Taken at 1751 on 14 September. Courtesy of A. Tomiya, GSJ.
Asama erupted almost continuously for a third straight day on 16 September
(figure 4), associated with more than 1,000 earthquakes. Incandescent
fragments were ejected ~300 m from the summit and ash columns rose ~1,200 m
above the crater. Late that night, winds carried ash as far as central
Tokyo, ~140 km SE. The frequency of the eruptions appeared to have tapered
off by the afternoon of the 17th. Television footage at that time showed
gray smoke mixed with ash billowing over the mountain. Minor ash eruptions
occurred intermittently until 2103 on 18 September; ash clouds drifted E.
Ashfall covered the southern part of the Kanto area, more than 150 km from
the volcano.
Figure 4. A panoramic photograph of Asama taken 16 September 2004 looking
from Asama's NE flank. Courtesy of Michiko Owada, GSJ.
By 18 September, the Japan Meteorological Agency (JMA) was reporting that
ash plumes were still rising ~1,200 m, but only about 23 small eruptions
and nearly 140 tremors had been recorded that afternoon, a significant
change from the nearly continuous activity of the previous few days. The
hazard status remained at 3 on a scale of 5, suggesting more
small-to-medium eruptions might occur.
An analysis of crater morphology based on airborne radar conducted on 16
September confirmed a new lava dome there. According to JMA and the
Geographical Survey Institute this was the first dome since 1973.
Mid-September radar images showed the growth of a broad (pancake-shaped)
layered form reaching several dozen meters high with a radius of ~100 m in
the NE part of the crater; its volume was ~500,000 m^3. Compelling images
showcasing the side-looking airborne (SAR) radar method and depicting the
dome can be seen on the GSI website (but as of early 2005 almost all the
text remained in Japanese).
A moderate explosive eruption occurred at 1944 on 23 September. Small
amounts of ash and lapilli were deposited NE of Asama.
Many (not all) parts of the world now have Volcanic Ash Advisory Centers
(VAACs) devoted to helping aviators avoid volcanic ash. They operate
through agencies closely associated with aviation meteorology. The Tokyo
VAAC website presents a diagram showing some fundamental linkages in its
information management networks (figure 5). The diagram is only intended to
provide an introductory overview (e.g., it is not comprehensive, and it may
be outdated); however, it should make the role of the Tokyo VAAC in the
Asama eruption more tangible to many in the volcano-monitoring community.
Figure 5. A schematic showing some paths of information flow into and out
of the Tokyo VAAC. The real communication patterns are considerably more
complex and involve other communication links, such as those of the air
carrier, between its aircraft to its own offices, and those directly
between local observatories and meteorological offices. Inputs from people
monitoring a volcano pass through a system with different conventions and
procedures. Modified from a diagram on the Tokyo VAAC website.
Volcano-monitoring input can pass to the VAAC via the paths labeled
Domestic (in this case, Japan) and International (including the Kamchatkhan
Volcanic Eruptions Response Team, the Philippine Institute of Volcanology
and Seismology, the Alaska Volcano Observatory, and adjacent VAACs of
Washington, Anchorage, and Darwin). In some examples of the latter
communications, one VAAC may alert others that an ash plume may soon extend
beyond the boundary of VAAC's area of responsibility. Sources of incoming
data include that from satellites and from aircraft. The latter includes
both PIREPS, pilot reports, and AIREPs, air reports routed via airlines.
The VAAC prepares output to aviators that includes both Volcanic Ash
Advisories and SIGMETS. The latter, SIGnificant METeorological messages
contain information about hazardous phenomena, including weather, severe
icing, turbulence, or volcanic ash that, in the judgment of the forecaster,
are hazardous to aviation). The system continues to undergo refinement and
exists under the auspices of the International Civil Aviation Organization
(ICAO).
Tokyo VAAC reported that eruptions during 23-25 September produced plumes,
in some cases to unknown heights; and in one case to "FL 170" (aviation
shorthand for 17,000 feet; ~5 km altitude; figure 6). In addition, minor
ash eruptions occurred twice on 1 October. Afterwards a helicopter flight
provided by the Nagano police (Shinshu) was carried out under conditions of
clear sky with southerly winds, enabling observers to watch Asama's summit
area during the hours of 0930-1100. They saw relatively weak emissions
drifting N. A new vent, ~70 m in diameter and ~40 m in depth lay within the
summit (Kamayama) crater. This was in accord with what had been observed on
16 and 17 September by radar (SAR image of GSI) and also photographed by
the press (Eg., Yomiuri Shimbun). From the eastern rim of the vent a crack
of incandescence was observed, from which a jet of volcanic gas issued
intermittently. Using an infrared camera, the highest temperature JMA
measured was 517°C.
Figure 6. A Volcanic Ash Advisory issued by Tokyo VAAC describing a 25
September 2004 eruption at Asama that sent ash to ~ 5 km altitude (FL 170).
Advisories such as this are the messages received on the flight deck of
potentially affected aircraft and by the air carriers' dispatchers.
Courtesy of the Tokyo VAAC.
A minor explosive eruption occurred at 2310 on 10 October. Small amounts of
ash and lapilli were deposited NNE of the volcano. The Tokyo VAAC reported
this eruption produced a plume to an unknown height.
The Tokyo VAAC reported an eruption on 16 October at 1206; it discharged a
SE-drifting ash cloud higher than 3.4 km altitude. On 18 October at 1017, a
N-drifting plume rose to ~3.4 km altitude.
Asama erupted with a loud explosion on 14 November at 2059. JMA rated the
eruption as mid-sized, 3 on a scale of 5, in terms of power of the
explosion. The agency issued a warning of falling ash downwind of the
volcano, although no ash plume was observed due to cloudy weather
conditions. Following the explosion observers did see falling rocks over a
large area on the volcano's slopes. There were no immediate reports of
injuries or damage. Ash and lapilli were deposited E of Asama and ash-fall
covered the N part of the Kanto area, reaching more than 100 km.
Other tilt, GPS, seismic, and gravity data. A tilt anomaly was observed and
announced by JMA on 22 February, but no eruption occurred. That inflation
took place over about 3 months, beginning 14 November 2004. The series of
eruptions in September 2004 was preceded by earthquake swarms and
shorter-term tilt changes. The respective anomalies became significant a
few days to half a day before the explosive events. Tiltmeters of JMA and
ERI are located ~3 km N and ~4 km E of the summit crater. The former are
more sensitive than the latter, probably due to Asama's inferred E- to
W-trending (dike-shaped) magma body. The inflationary tilt measured 3 km N
of the summit crater was as small as 10^-6 radians. The smaller tilt
episodes remained below the detection threshold for the GPS network
surrounding the volcano.
Preceding the Vulcanian explosions on 1, 23, and 29 September, observers
noticed frequent B-type earthquakes. They also documented small inflations
of the summit area. These inflations occurred about half day to one day
before the explosions. On the other hand, the explosive events during 16-17
September followed deflation in the wake of a three-day inflation (10-13
September).
S. Okubo conducted continuous gravity measurements at the Asama Volcano
Observatory (AVO) of ERI. Various explosive events of September reportedly
occurred a few days after gravity shifted from an increase to a decrease.
AVO's gravity station sits at 1,400 m elevation about 4 km E of the summit.
Okubo proposed that the gravity changes reflected movement of magma within
the conduit. Gravity decreased when the magma head rose above the
observation level.
Background. Asama, Honshu's most active volcano, overlooks the resort town
of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of
the Izu-Marianas and NE Japan volcanic arcs. The modern cone of
Maekake-yama forms the summit of the volcano and is situated E of the
horseshoe-shaped remnant of an older andesitic volcano, Kurofu-yama, which
was destroyed by a late-Pleistocene landslide about 20,000 years before
present (BP). Growth of a dacitic shield volcano was accompanied by
pumiceous pyroclastic flows, the largest of which occurred about
14,000-11,000 years BP, and by growth of the Ko-Asama-yama lava dome on the
E flank. Maekake-yama, capped by the Kama-yama pyroclastic cone that forms
the present summit of the volcano, is probably only a few thousand years
old and has an historical record dating back at least to the 11th century
AD. Maekake-yama has had several major plinian eruptions, the last two of
which occurred in 1108 and 1783 AD.
Information Contacts: Yukio Hayakawa, Faculty of Education, Gunma
University, Aramaki 4-2, Maebashi Gunma 371-8510, Japan (Email:
hayakawa@edu.gunma-u.ac.jp, URL: maechan.net/hayakawa/asama/
gankoran/, www.edu.gunma-u.ac.jp/~hayaka...h.html); Setsuya
Nakada, Volcano Research Center, Earthquake Research Institute (ERI),
University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113, Japan (Email:
nakada@eri.u-tokyo.ac.jp; URL:
www.eri.u-tokyo.ac.jp/topics/...e.html); Geological
Survey of Japan (GSJ), National Institute of Advanced Industrial Science
and Technology (GSJ AIST) (URL: www.gsj.jp/kazan/kazan-bukai/
yochiren/asama040909/ material.html); Asia Air Survey Co., Ltd. (Email:
info@ajiko.co.jp,ta.chiba@ajiko.co.jp,at.amano@ajiko.co.jp; URL:
www.ajiko.co.jp/ topics/ct/ asama/); Geographical Survey Institute
(radar and other methods), Ministry of Land,Infrastructure and Transport,
Japan (URL: www.gsi.go.jp/BOUSAI/ASAM...dexsar.htm); Japan
Meteorological Agency (JMA), Volcanological Division, Seismological and
Volcanological Department, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100-8122;
Tokyo Volcanic Ash Advisory Center, Tokyo Aviation Weather Service Center,
Haneda Airport 3-3-1, Ota-ku, Tokyo 144-0041, Japan
(www.jma.go.jp/JMA_HP/jma/...index.html);
International Civil Aviation Organization (ICAO), 999 University Street,
Montreal, Quebec H3C 5H7, Canada (URL: www.icao.int/); Reuters.
Raung
eastern Java, Indonesia
8.125°S; 114.042°E; summit elev. 3,332 m
All times are local (= UTC + 8 hours)
Though frequently active, Raung is seldom the subject of reports from
either the news media or the Directorate of Volcanology and Geological
Hazard Mitigation (DVGHM). The most recent Darwin VAAC report was issued
late on 26 August 2002 (UTC). It noted that aviators had estimated an ash
plume at ~10 km altitude drifting W (reported 25 August in an AIREP). Ash
clouds were not visible on NOAA/GMS satellite imagery. A summary of Darwin
VAAC reports of Raung for the period July 1999-August 2002 was given in
Bulletin v. 29, no. 1.
There were nine anomalous Moderate Resolution Imaging Spectroradiometer
(MODIS) observations of volcanic hot spots at Raung during 3 June-8 October
2004 (table 1). The 2004 alerts were the first detected by MODIS at Raung.
Minor explosive activity documented intermittently during 1999 to 2002
(Bulletin v. 29, no. 1) did not have a thermal component sufficient to
trigger alerts.
Table 1. Thermal anomalies at Raung observed with MODIS during 2004. Some
of the UTC times were for the previous date. Spectral radiance for the hot
pixels in band 21 (central wavelength of 3.959 um) are in units of watts
per square meter per steradian per micron (W-2 sr-1 um-1). Courtesy of the
Hawaiian Institute of Geophysics and Planetology.
Date (2004) Time (local / UTC) Spectral radiance
15 Apr 2300 / 1500 0.852
16 Apr 0200 / 1800 (15 Apr) 0.847
22 Apr 2310 / 1510 0.814
02 May 0200 / 1800 (01 May) 0.813
03 Jun 0200 / 1800 (02 Jun) 0.677
18 Jun 2300 / 1500 0.729
04 Jul 2300 / 1500 0.795
11 Jul 2310 / 1510 0.814
14 Jul 0155 / 1755 (13 Jul) 0.778
22 Sep 2300 / 1500 0.849
23 Sep 0200 / 1800 (22 Sep) 0.740
29 Sep 2305 / 1505 0.893
08 Oct 2300 / 1500 0.776
No ground observations have been reported during 2004, but in a message
from Dali Ahmad (DVGHM), he noted the absence of observed emissions during
2004. With respect to the thermal alerts, he speculated that they could
conceivably have originated from brush fires. Rob Wright commented that the
levels of radiance in the 2004 alerts were both "too weak and too
intermittent to be lava flows" and stood near the system's lower threshold.
Similar weak anomalies occur at volcanoes such as Villarrica and during
intervals at Anatahan, but the source of the alerts at Raung remains uncertain.
Clear aerial photographs of Raung were taken on 26 and 30 July 2001 (figure
7) by Franz Jeker of Singapore Airlines as he flew past in descent towards,
or ascent from, the Bali airport. Jeker also included a detailed map of the
Raung area (figure 8).
Figure 7. A photograph taken on 26 July 2001 of a small fumarolic plume
from the central crater of Raung looking SW during a fly-by of a commercial
airplane across the NNE flank. Courtesy of F. Jeker.
Figure 8. Map showing relative locations of Raung volcano at the SW end of
Java, and adjacent Bali. Courtesy of F. Jeker.
Background. Raung, one of Java's most active volcanoes, is a massive
stratovolcano in easternmost Java that was constructed SW of the rim of
Ijen caldera. The 3,332-m-high, unvegetated summit of Gunung Raung is
truncated by a dramatic steep-walled, 2-km-wide caldera that has been the
site of frequent historical eruptions. A prehistoric collapse of Gunung
Gadung on the W flank produced a large debris avalanche that traveled 79 km
from the volcano, reaching nearly to the Indian Ocean. Raung contains
several centers constructed along a NE-SW line, with Gunung Suket and
Gunung Gadung stratovolcanoes being located to the NE and W, respectively.
Information Contacts: Directorate of Volcanology and Geological Hazard
Mitigation (DVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (Email:
dali@vsi.dpe.go.id; URL: www.vsi.esdm.go.id/); Darwin Volcanic Ash
Advisory Center (VAAC), Bureau of Meteorology, Northern Territory Regional
Office, PO Box 40050, Casuarina, NT 0811, Australia (URL:
www.bom.gov.au/info/vaac/...ries.shtml; Email:
Darwin.vaac@bom.gov.au); Hawai'i Institute of Geophysics and Planetology
(URL: modis.higp.hawaii.edu); Franz Jeker, Rigistrasse 10, 8173
Neerach, Switzerland (Email: franz.jeker@swissonline.ch).
Kerinci
Sumatra, Indonesia
1.814°S, 101.264°E; summit elev. 3,800 m
All times are local (= UTC + 7 hours)
Events at Kerinci were previously discussed through 29 August 2004
(Bulletin v. 29, no. 8). The following report overlaps slightly, covering
17 July through 24 October 2004. As already reported, on 24 July 2004 a
thick plume rose to 100-600 m above the crater rim, ash fell ~3 km from the
crater forming deposits as thick as 1 cm. Seismicity is summarized in table 2.
Table 2. Volcanic seismicity registered at Kerinci during 17 July to 24
October 2004. Courtesy of DVGHM.
Date (2004) Volcanic A Volcanic B Emission
17 Jul-24 Jul 2 1 0.5-3
24 Jul-31 Jul 5-6 3 0.5-5
02 Aug-08 Aug 5 2 continue
09 Aug-15 Aug 1 1 continue
16 Aug-22 Aug 2 2 continue
23 Aug-29 Aug -- 1 continue
27 Sep-03 Oct 5 1 continue
04 Oct-10 Oct -- 1 continue
11 Oct-17 Oct -- 2 continue
18 Oct-24 Oct 3 2 continue
There were six Darwin VAAC reports on Kerinci in 2004, two on 21 June and
four on 27 September. (Prior to that the VAAC reports were clustered in
mid- to late-August 2002.) The 21 June cases discussed a continuous
emission with ash to ~4 km drifting W. The 27 September cases began with
and then repeated an aviator's statement (an AIREP at 0136 UTC 27
September), noting that ash was observed to ~6 km, drifting W. For all six
cases (June and September), the VAAC staff noted that due to cloud cover,
ash was not visible in satellite data.
Kerinci erupted on 6 August 2004 at 0835 hours. Gray ash rose to 50-600 m
above the summit. The hazard status was raised to Alert Level II (yellow)
at 1030, where it stayed for the remainder of this report period.
During 9-15 August 2004 the number of earthquakes decreased. A white thin
plume again rose to 50-300 m above the summit. Volcanic activity remained
relatively stable from 15 August through 24 October 2004, with thick gray
plumes rising 50-300 m above the summit.
Background. The 3,800-m-high Gunung Kerinci in central Sumatra forms
Indonesia's highest volcano and is one of the most active in Sumatra.
Kerinci is capped by an unvegetated young summit cone that was constructed
NE of an older crater remnant. The volcano contains a deep 600-m-wide
summit crater often partially filled by a small crater lake that lies on
the NE crater floor, opposite the SW-rim summit of Kerinci. The massive 13
x 25 km wide volcano towers 2400-3300 m above surrounding plains and is
elongated in a N-S direction. The frequently active Gunung Kerinci has been
the source of numerous moderate explosive eruptions since its first
recorded eruption in 1838.
Information Contacts: DVGHM (see Raung).
Marapi
Sumatra, Indonesia
0.38°S, 100.47°E; summit elev. 2,891 m
The most recent previous explosive activity at Marapi peaked during 13-18
April 2001, when a total of 150 explosions occurred that sent ash plumes to
2 km above the summit (Bulletin v. 27, no. 1). This report covers the
interval 5 August to 10 October 2004.
On 5 August 2004 Marapi generated a small eruption with a gray to black ash
cloud that rose to 500-1,000 m above the summit. Its hazard status was
raised to Alert Level II (yellow), where it remained throughout this period.
Total numbers of seismic events from 2 August through 10 October 2004 are
listed in table 3. During some weeks in August the number of earthquakes
increased markedly. A thin white plume rose to 50 m above the summit on 10
August. During 16-29 August a thin white-gray plume rose to ~75-100 m.
Similar plumes rose to ~50 m during 27 September-3 October and to ~300 m
during 4-10 October. Seismic signals inferred to be related to emissions
were elevated during several weeks of the reporting interval, particularly
in August (table 3).
Table 3. A summary of volcanic seismicity at Marapi during 2 August to 10
October 2004. Courtesy of DVGHM.
Date Volc A Volc B Tremor Emission
02 Aug-08 Aug 1 11 -- --
09 Aug-15 Aug 2 6 -- 20
16 Aug-22 Aug -- 3 -- 21
23 Aug-29 Aug -- 3 2 14
20 Sep-26 Sep -- -- -- --
27 Sep-03 Oct 1 -- -- --
04 Oct-10 Oct 3 -- -- 8
There were no MODIS-MODVOLC alerts at Marapi during 2004.
Background. Gunung Marapi, not to be confused with the better-known Merapi
volcano on Java, is Sumatra's most active volcano. Marapi is a massive
complex stratovolcano that rises 2,000 m above the Bukittinggi plain in
Sumatra's Padang Highlands. A broad summit contains multiple partially
overlapping summit craters constructed within the small 1.4-km-wide Bancah
caldera. The summit craters are located along an ENE-WSW line, with
volcanism migrating to the W. More than 50 eruptions, typically consisting
of small-to-moderate explosive activity, have been recorded since the end
of the 18th century; no lava flows outside the summit craters have been
reported in historical time.
Information Contacts: DVGHM (see Raung); Darwin Volcanic Ash Advisory
Center (VAAC) (see Raung).
Etna
Italy
37.734°N, 15.004°E; summit elev. 3,350 m
The effusive eruption that started on 7 September 2004 on the W wall of the
Valle del Bove continued. Lava escaped at a very low effusion rate from two
main vents at 2,620 and 2,320 m elevation. Lava tubes developed downslope
of these vents, forming a complex lava-flow field with ephemeral vents at
the base of the W wall of the Valle del Bove. After December 2004, effusive
vents were mainly located at the lower end of the tube network below 2,000
m elevation. Lava flows were up to 2.5 km long, and the lava-flow field did
not change significantly since the end of October 2004 (figure 9).
Figure 9. A map of Etna emphasizing features associated with the lava flow
field as they appeared 4 October 2004. Courtesy of INGV.
On 8 January 2005 an ash plume formed above the summit of SE crater and
lasted a few hours. Analysis of the ash components revealed that it
consisted of lithic material. This episodic ash emission was probably
caused by collapse within the crater into the void left after three months
of lava output.
On 18 January the INGV-CT web camera located 27 km S of the summit craters
revealed a dense, pulsating gas plume rising above the summit of NE crater
and lasting a few minutes. This was probably caused by snow vaporization
due to hot gas emission from the main crater vent.
During the afternoon of 18 January a new lava flow formed upslope along the
2,620-m-long eruptive fissure, at ~2,450 m elevation. The lava flow spread
for about 200 m SE on the snow and along the middle wall of the western
Valle del Bove. This flow front moved slowly and completely stopped after
about 24 hours. The emission of lava from the ephemeral vents below 2,000 m
stopped during the effusion from the 2,450-m vent. The lower ephemeral
vents again started to emit lava on 19 January. During the afternoon of 22
January two new lava flows erupted from vents at 2,400 m elevation, along
the same tube system fed by the 2,620-m-elevation vent. Two parallel,
fast-moving flows spread E. They were still evident on 27 January from the
images recorded by the INGV-CT webcam at Milo, together with a number of
ephemeral vents and small lava flows at the lower end of the lava tube.
The opening of effusive vents upslope along the tube system of a complex
lava-flow field has usually indicated the final stages of expansion, an
effect observed several times at lava-flow fields on Etna and Stromboli.
Decreased effusion from the main vent causes the tube system to drain, so
the lava tube walls collapse. Obstruction at the lower end of the tube then
causes accumulation of lava farther upslope and the opening of new vents at
higher elevations.
Since the start of the eruption on 7 September 2004 (Bulletin v. 29, no.9),
there has been no significant explosive activity at the summit craters or
the eruptive fissures.
Background. Mount Etna, towering above Catania, Sicily's second largest
city, has one of the world's longest documented records of historical
volcanism, dating back to 1500 BC. Historical lava flows of basaltic
composition cover much of the surface of this massive volcano, whose
edifice is the highest and most voluminous in Italy. The most prominent
morphological feature of Etna is the Valle del Bove, a 5 x 10 km
horseshoe-shaped caldera open to the E. Two styles of eruptive activity
typically occur at Etna. Persistent explosive eruptions, sometimes with
minor lava emissions, take place from one or more of the three prominent
summit craters, the Central Crater, NE Crater, and SE Crater (the latter
formed in 1978). Flank vents, typically with higher effusion rates, are
less frequently active and originate from fissures that open progressively
downward from near the summit (usually accompanied by Strombolian eruptions
at the upper end). Cinder cones are commonly constructed over the vents of
lower-flank lava flows. Lava flows extend to the foot of the volcano on all
sides and have reached the sea over a broad area on the SE flank.
Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e
Vulcanologia, Piazza Roma 2, 95123 Catania, Italy (URL:
www.ct.ingv.it/, Email: calvari@ct.ingv.it).
Erta Ale
Ethiopia
13.60°N, 40.67°E; summit elev. 613 m
An expedition led by the volcanology travel group SVE-SVG visited Erta Ale
during 22-23 January 2005. The observed eruptive activity was generally
unchanged since November 2004 (Bulletin v. 29, no. 11). Degassing was still
occurring from three of the four hornitos in the SW part of the South
crater, but had decreased slightly in comparison with their December 2004
observations. The hornitos stood ~10 m high and represented the only
portion of the lava crust covering the crater floor where gas emissions
were seen. A window in the upper part of one of the hornitos permitted
observation of glowing molten lava.
On 23 January 2005 members of the group descended into the crater and
collected recent lava that had poured out from the hornitos during partial
collapse. Degassing activity (mainly SO2) from the North crater had also
slightly decreased in comparison with early December 2004 observations.
From a small terrace in the NW part of the crater it was possible to
observe degassing from several hornitos (some several meters high in the
central part of the 'lava bulge'). Near the NW wall of the crater two
small, red glowing areas were visible at the summit of two other hornitos.
Chemical analyses. The following complements a previous Erta Ale report by
Jacques-Marie Bardintzeff from November-December 2004 (Bulletin v. 29,
no.11). He sampled molten lava at 12 m depth in one of the hornitos of the
crater on 5 December 2004 using a cable and an iron mass, and subsequently
analyzed the chilled glass sample using an electron microprobe (table 4).
Table 4. Major-element chemistry of Erta Ale lava resulting from 18
representative glass analyses. Courtesy of Jacques-Marie Bardintzeff.
Oxide Weight percent
SiO2 48.61-49.64
Al2O3 12.99-13.60
TiO2 2.37- 2.66
MgO 6.13- 6.39
FeO 11.25-12.20
Cr2O 0- 0.11
MnO 0.03- 0.34
CaO 10.63-11.41
Na2O 2.81- 3.08
K2O 0.54- 0.69
Total 97.44-98.71
Analysis also revealed some plagioclase phenocrysts (An = 80.9-70.4) as
well as scarce clinopyroxene microcrysts (Wo = 43.5-44.0, En = 45.8-45.9,
Fs = 10.2-10.6). Compared to the matrix glasses shown in table 4, glass
inclusions trapped in plagioclase were richer in SiO2 (50.07-50.41 wt%) and
poorer in TiO2 (1.84-1.95 wt %).
Correction. French scientists led by Jacques-Marie Bardintzeff and Franck
Pothe visited the summit of Erta Ale on 13-14 January 2003 (Bulletin v. 28,
no.4). At that time the lava lake in the S pit crater was 180 m long, not
120 m as previously reported.
Background. Erta Ale is an isolated basaltic shield volcano that is the
most active volcano in Ethiopia. The broad, 50-km-wide volcano rises more
than 600 m from below sea level in the barren Danakil depression. Erta Ale
is the most prominent feature of the Erta Ale Range. The volcano contains a
0.7 x 1.6 km, elliptical summit crater housing steep-sided pit craters.
Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend
of the Erta Ale range is located to the SE of the summit and is bounded by
curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows
from these fissures have poured into the caldera and locally overflowed its
rim. The summit caldera is renowned for long-term lava lakes that have been
active since at least 1967, or possibly since 1906. Recent fissure
eruptions have occurred on the northern flank.
Information Contacts: Jacques-Marie Bardintzeff, Laboratoire de
Petrographie-Volcanologie, Bât. 504, Universite Paris-Sud, F-91405, Orsay,
France (Email: bardizef@geol.u-psud.fr, URL:
www.lave-volcans.com/bardintzeff.html); Franck Pothe, Terra
Incognita, CP 701, 36 quai Arloing 69256 Lyon Cedex, France (Email:
ti@terra-incognita.fr); Henry Gaudru, Georges Kourounis, Derek Tessier,
Brian Fletcher, Alexander Gerst, and Motomaro Shirao, Societe
Volcanologique Europeenne (SVE)-Societe Volcanologique (SVG), Geneva,
C.P.1, 1211 Geneva 17, Switzerland (URL: www.sveurop.org/, Email:
HgaudruSVE@compuserve.com).
Popocatepetl
central Mexico
19.023°N, 98.622°W; summit elev. 5,426 m
All times are local (= UTC 6 hours)
During 2004, Popocatepetl showed an overall low level of activity. Apart
from a few low-intensity exhalations, no significant seismicity,
deformation, or geochemical changes in spring waters were detected. The
crater (figure 10) did not show significant morphological changes other
than hydrologic effects, and no evidence of lava dome emplacements were
observed. During December, relatively low-level volcanism prevailed,
including low-intensity steam-and-gas emissions (table 5). An aerial
photograph taken on 10 December showed subsidence in the inner crater and
no external lava dome at the bottom of the crater. The Alert Level remained
at Yellow Phase II.
Figure 10. Annotated aerial photograph of Popocatepetl's summit area taken
12 November 2004. Courtesy of CENAPRED; the Mexican Secretary of
Communications and Transportation; and Servando De la Cruz, UNAM.
Table 5. Summary of various observations at Popocatepetl during December
2004 (chiefly visual confirmations of ongoing emission). Courtesy of CENAPRED.
Date (2004) Exhalations Other Observations
01 Dec-04 Dec Low-intensity (9-13 per day) Light steam-and-gas emissions
05 Dec-07 Dec Low-intensity (16-19 per day) Light steam-and-gas emissions
08 Dec-09 Dec Low-intensity (7-10 per day) Light steam-and-gas emissions
10 Dec Low-intensity (11) Aerial photograph showed
subsidence in the inner
crater; no external lava
dome at the bottom of the
crater can be distinguished
11 Dec-16 Dec Low-intensity (3-10 per day) Light steam-and-gas emissions
17 Dec-21 Dec Low-intensity (2-5 per day) Light steam-and-gas emissions
22 Dec-27 Dec Low intensity (6-10 per day) Light steam-and-gas emissions
28 Dec Low-intensity (19) Light steam-and-gas emissions
29 Dec-31 Dec Low-intensity (9-11 per day) Light steam-and-gas emissions
At the end of December 2004, however, a slight increase in seismic activity
was detected (table 5). On 20 and 29 December 2004 two exhalations, small
yet exceeding the average for the year, were followed in early January 2005
by a series of phreatic explosions. The major events were detected on 9
January at 2245 and on 22 January at 2358. These were the largest events
detected in the past 15 months. In both cases, light ashfall was reported
on the towns of Cuautla (<40 km SSW of the volcano), and San Martin
Texmelucan (37 km NE of the crater). In an aerial photograph taken on 14
January 2005 the inner crater appears deeper than previously shown, with no
evidence of magmatic activity (figure 11).
Figure 11. Annotated photograph of Popocatepetl's summit area taken 14
January 2005. A label identifies a small craterlet on the southern inner
wall of the inner crater. These type of craterlets have been repeatedly
formed by moderate explosions or exhalations. They have tended to be
ephemeral, lasting only until the next event. Courtesy of CENAPRED; the
Mexican Secretary of Communications and Transportation; and Servando De la
Cruz, UNAM.
Background. Volcan Popocatepetl, whose name is the Aztec word for smoking
mountain, towers to 5,426 m 70 km SE of Mexico City to form North America's
2nd-highest volcano. The glacier-clad stratovolcano contains a
steep-walled, 250-450 m deep crater. The generally symmetrical volcano is
modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier
volcano. At least three previous major cones were destroyed by
gravitational failure during the Pleistocene, producing massive
debris-avalanche deposits covering broad areas south of the volcano. The
modern volcano was constructed to the south of the late-Pleistocene to
Holocene El Fraile cone. Three major plinian eruptions, the most recent of
which took place about 800 AD, have occurred from Popocatepetl since the
mid Holocene, accompanied by pyroclastic flows and voluminous lahars that
swept basins below the volcano. Frequent historical eruptions have occurred
since precolumbian time.
Information Contacts: Alicia Martinez Bringas, Angel Gomez Vazquez, Roberto
Quass Weppen, Enrique Guevara Ortiz, Gilberto Castelan Pescina, and Cesar
Morquecho Zamarripa, Centro Nacional de Prevencion de Desastres (CENAPRED),
Av. Delfin Madrigal No.665. Coyoacan, Mexico D.F. 04360. Email:
amb@cenapred.unam.mx gvazquez@cenapred.unam.mx; URL:
www.cenapred.unam.mx/); Servando De la Cruz-Reyna, Instituto de
Geofisica, UNAM Cd. Universitaria. Circuito Institutos, Coyoacan, D.F.
04510, Mexico (Email: sdelacrr@tonatiuh.igeofcu.unam.mx, URL:
www.geofisica.unam.mx).
Colima
western Mexico
19.514°N,103.62°W; summit elev. 3,850 m
New emissions of block-lava flows began on 30 September 2004 after 19
months of intermittent explosive activity. During February 2002-February
2003 the lava dome extruded effusively, but it was destroyed by the
July-August 2003 explosions (Bulletin v. 28, no. 6; and v. 29, no. 5).
Thus, beginning in September 2003 the upper crater lacked a visible dome.
The new lava effusions that began on 30 September took place without either
premonitory swarms of volcano-tectonic earthquakes or significant
deformation of the volcanic edifice. A 6-hour episode of volcanic tremors
was observed on 20 September (figures 12 and 13).
Figure 12. Plots of Colima activity during September-November 2004: (A)
Lava emission rate; and (B) Number of earthquakes produced by rockfalls and
pyroclastic flows (PF) (heavy line) and by explosions and exhalations
(dashed line). Arrows show the tremor episode and the start of the
eruption. Courtesy of Colima Volcano Observatory.
Figure 13. Seismic record showing the start of the tremor episode (towards
the bottom) as registered at station EZV4 situated at a distance of 1.4 km
from the crater. Courtesy of Colima Volcano Observatory.
On 28 September, intensive fumarolic activity began in the crater, forming
a 500-m-high column of white gas. An overflight that day permitted
observation of a new lava extrusion that practically filled the crater. An
intensive swarm of seismic events produced by rockfalls and pyroclastic
flows began at about 0600 on 30 September. The seismic events indicated the
overflow of lava from the crater and heralded the formation of two
andesitic block-lava flows. These flows began to develop along Colima's N
and WNW slopes.
During October and November, lava emission continued at a decreasing rate
(figure 12). The lava emissions were effusive and accompanied by frequent
small explosions and exhalations. Numerous block-and-ash flows extended
~4.5 km from the summit (figure 14). Seismic intensity closely tracked with
variations in the lava emission rate.
Figure 14. An oblique aerial photo showing a new lobe of blocky lava
emplaced on Colima's N flank. Photo was taken on 27 October 2004. Courtesy
of Colima Volcano Observatory.
By 1 December, the two lava flows stretched ~2,400 m long and ~300 m wide
on the N flanks, and ~600 m long and 200 m wide on the WNW flanks (figure
14). The total volume of erupted material including lava and
pyroclastic-flow deposits was ~8.3 x 10^6 m^3.
Background. The Colima volcanic complex is the most prominent volcanic
center of the western Mexican Volcanic Belt. It consists of two
southward-younging volcanoes, Nevado de Colima (the 4,320-m-high point of
the complex) on the N and the 3,850-m-high historically active Volcan de
Colima at the south. A group of cinder cones of probable late-Pleistocene
age is located on the floor of the Colima graben west and east of the
Colima complex. Volcan de Colima (also known as Volcan Fuego) is a youthful
stratovolcano constructed within a 5-km-wide caldera, breached to the
south, that has been the source of large debris avalanches. Major slope
failures have occurred repeatedly from both the Nevado and Colima cones,
and have produced a thick apron of debris-avalanche deposits on three sides
of the complex. Frequent historical eruptions date back to the 16th
century. Occasional major explosive eruptions (most recently in 1913) have
destroyed the summit and left a deep, steep-sided crater that was slowly
refilled and then overtopped by lava dome growth.
Information Contact: Observatorio Vulcanologico de la Universidad de
Colima, Colima, Col., 28045, Mexico (Email: ovc@cgic.ucol.mx).
__________________________________________________________
Global Volcanism Program, NHB E-421 Tel: (202) 633-1800
Smithsonian Institution Fax: (202) 357-2476
Washington, DC 20560-0119 Email: gvp@si.edu
Internet: www.volcano.si.edu/
-
Re: GVN Bulletin
Mon, April 11, 2005 - 10:37 AM********************************************************
Bulletin of the Global Volcanism Network, February 2005
********************************************************
From: Ed Venzke <venzke@volcano.si.edu>
Bulletin of the Global Volcanism Network
Volume 30, Number 2, February 2005
Manam (Papua New Guinea) One death, 14 injuries due to 27 January eruption;
stratospheric injection
Rinjani (Indonesia) Witnessed eruptions in October 2004 with material
escaping from two vents
Anatahan (Mariana Islands) Remotely sensed ash plumes in February; Guam
air-quality problems
Asama (Japan) Maps of 2004 tephra deposits; radar images of the crater's
interior and a dome
Shiveluch (Kamchatka) 27 February eruption left deposits covering 24,800
km2 to W of volcano
Veniaminof (Alaska) Ash emissions in January and Strombolian eruptions in
February
St. Helens (USA) On 21 February the still-growing dome stood 160 m higher
than the 1980's dome
Kick 'em Jenny (W Indies) Monitored and quiet; multi-beam finds craters and
domes
Marion Island (South Africa) Small eruption seen 24 June 2004 on S side of
this Antarctic island
Editors: Rick Wunderman, Edward Venzke, and Gari Mayberry
Volunteer Staff: Robert Andrews, Jacquelyn Gluck, William Henoch, and
Catherine Galley
Manam
Papua New Guinea
4.10°S, 145.061°E; summit elev. 1,807 m
All times are local (= UTC + 10 hours)
On 24 October 2004 a strong eruption occurred at Manam (Bulletin v. 29, no.
10). Several more significant eruptions followed in late 2004 (Bulletin v.
29, no. 11), leading to the most severe and damaging one, which took place
on 27 January 2005. That event occurred in conditions favorable to
satellite imagery, enabling Andrew Tupper of the Darwin Volcanic Ash
Advisory Centre (VAAC), and colleagues, to confirm that the associated ash
cloud reached to over 20 km altitude, well into the stratosphere.
Satellite remote sensing documented 5 eruption plumes ascending to over 15
km during this issue's reporting interval, 23 October 2004-28 January 2005.
One additional plume may have been missed by remote sensing in adverse
weather conditions. Various images from the 2004 and 2005 eruptions are on
the Darwin VAAC website (see Information Contacts, below). Sulfur dioxide
is discussed there as well as on websites of the OMI-TOMS Volcanic
Emissions Group and related sites.
The Bulletin has benefitted from reports by the Rabaul Volcano Observatory
(RVO), the media, and the Darwin VAAC. Although the 27 January eruption
received comparatively little press coverage, it caused several injuries
and one death. RVO staff working at Manam faced challenging, hazardous
conditions. The island had been home to ~ 9,500 now-displaced residents.
Summary of RVO observations. During the reporting interval both lava flows
and pyroclastic flows reached the sea at various times (Bulletin v. 29,
nos. 10 and 11). The main pathways were the NE and SE valleys (table 1,
figures 1 and 2). Intervals of tremor were common.
Table 1. A summary of RVO observations involving lava flows and pyroclastic
flows associated with Manam's eruptions during 23 October 2004-28 January
2005. Andrew Tupper (of the Darwin VAAC) compiled this list from available
RVO reports and communications with RVO staff.
Date Event at Manam
24 Oct 2004 Pyroclastic flows reached the sea and lava flowed
600 m down the SE valley.
31 Oct 2004 Three lobed lava flow in NE valley, and possibly a
small flow in the NW
valley.
11 Nov 2004 Lava in NE valley.
23-24 Nov 2004 Lava in NE valley. "The flow that headed towards
Bokure 1 terminated about
100 m away from the main road . . . the Kolang
lava flow had reached the
sea" (reported by Warisi observer Herman Tibong).
Ash on roofs caused a
number of houses to collapse.
19-20 Dec 2004 Lava and pyroclastic flows in SE valley. Pyroclastic
flows stopped 200 m
from the sea on the 19th (no report on what
happened on the 20th).
27-28 Jan 2005 14 injured and 1 dead at Warisi; debris voluminous
and widespread on the
island; ashfall reported ~230 km W of Manam.
Figure 1. Map of Manam island made or updated circa 2002 (contour interval,
200 m). A temporary observatory was at Warisi (triangle, 'current seismic
station') on the island's E side, but the eruption on 27 January 2005
destroyed it. Approximate trends of radial valleys were added by Bulletin
editors. Courtesy of RVO.
Figure 2. Annotated image of Manam indicating village and other place names
on a false-color satellite photo (note the cloud cover; for scale, compare
to previous figure). Source details are unknown. "Waris," is more commonly
spelled "Warisi" in RVO reports. Courtesy of the PNG Mapserver website.
Eruption on 27 January 2005. RVO reported that eruptive activity during the
evening of 27 January was more severe than previous eruptions of the
current eruptive period. As indicated on table 1, during 27-28 January
there were 14 people injured and one person killed at Warisi village. RVO's
monitoring base at Warisi was completely destroyed, taking out its HF
radio, seismograph, and a satellite phone, thus preventing RVO from
providing information on the current level of activity. The phone had been
donated by an airline just a few weeks prior, provided as a means of aiding
eruption-warning efforts. The station sat on the E flank at Warisi village
(figures 1 and 2). RVO later recovered the station's seismograph and
installed it on the island's NW side; they also restored radio communications.
According to the Papua New Guinea (PNG) news source, The National, some
people had returned on 27 January from the displacement camps on the
mainland to gather food from their island gardens, only to have their boat
destroyed by impacts from erupted rocks. The National also reported that
many of the residents of the island who were originally evacuated in
November 2004 had returned. There were reports of several houses that had
burned down from hot emissions and others that collapsed under the weight
of ash and pyroclastic material. It was reported that after the large
eruption on 27 January, local authorities planned to evacuate about 2,000
residents.
Ash fell at ~230 km W of Manam (in Ambunti district, East Sepik province,
PNG). Tupper recognized NW monsoon winds that took low-level ash SE. Thus,
the ash that fell in Ambunti must have traveled at a higher altitude, which
Tupper estimated to be above 6 km altitude.
The October-January eruptive sequence. Figure 3 plots eruption heights
versus time during 23 October 2004 to late January 2005. Three kinds of
eruption-height estimates appear: those from pilot reports, RVO's estimates
(ground-based observations), and Tupper's post-analysis studies of
satellite data. In a descussion below, Tupper mentions the differences
between the three height-estimate techniques. The line showing alert level
corresponds to the right-hand scale. Six eruptive clouds are clear on the
graph.
Figure 3. A graph of Manam's cloud heights from 23 October 2004 to
late-January 2005, as determined from various means (see key along top).
The dashed line corresponds to the right-hand scale of the graph, which
displays alert levels reported by RVO (0-4, with 4 as the highest).
Courtesy of Andrew Tupper, Darwin VAAC.
The 24 October eruption at Manam occurred just before the Terra and Aqua
satellites passed over. The data from those satellites, and from AVHRR and
GOES satellites, indicated a very ice-rich cloud. Associated with Manam's
eruption on 24 October, the coldest temperature measured from the
high-level cloud was about 204 K (a couple of hours after the eruption),
which translated to an altitude of about 15-18 km (a height supported by
the ash cloud's subsequent dispersion, including wind trajectories
consistent with the ~18 km altitude plotted on figure 3). There was no
evidence of significant stratospheric penetration. Pilot reports for the
cloud's top were generally lower, as is usual for large eruptions (Tupper
and Kinoshita, 2003).
Figure 4 presents a photo of the 11 November eruption plume as seen by Air
Niugini pilot David Innes. He estimated the visible portion of the plume
height at "30,000 feet" (~9 km), but the cloud probably ascended at least a
bit higher as it entered into masking cirrus clouds from a tropical
disturbance to the N, so the pilot's estimate might be stated as 'above 9
km.' RVO's ground observer estimated a plume at ~8 km slightly earlier in
the eruption, on about 10 November. The satellite-based analysis was
thwarted by the cirrus cloud cover during this eruption.
Figure 4. A N-looking aerial photo showing Manam's plume at 0630 local time
on 11 November 2004. The plume extends to ~9 km before disappearing into
higher weather clouds. Photo by David Innes of Air Niugini; used here with
his permission.
From 20 December until just before the 27 January eruption, no plumes or
hot spots were visible. Few plumes were reported by RVO, and none were seen
by pilots (table 1). The 27 January eruption began about 1400 UTC; and an
Aqua/MODIS image from 0507 UTC is shown as figure 5.
Figure 5. An infrared Aqua/MODIS image of the umbrella cloud from the 27
January 2005 Manam eruption (taken at 1535 UTC on the night of the 27th).
The image is enhanced to show the 'warm spot' in the centre of the cloud
(warm because of the stratospheric intrusion) and the gravity waves in the
cloud. The lobate structure at the fringes of the cloud is similar to other
observed umbrella clouds, such as the 1991 Pinatubo cloud. At this stage
the cloud had a diameter of approximately 180 km. Courtesy of Andrew Tupper.
The Darwin VAAC initially estimated the 27 January eruption cloud's maximum
height as 21 km altitude, but later analysis found the range 21-24 km a
better estimate. Infrared 11-um imagery from GOES-9 at 1440 UTC and
Aqua/MODIS at 1539 UTC on 27 January showed 'warm' spots in the middle of
the umbrella cloud of 215.4 K and 210.4 K, respectively, indicating a
substantial overshoot of the cloud top into the warmer stratosphere
(tropopause temperatures were around 187 K). The GOES-9 temperature may be
less useful because of poorer satellite resolution and calibration, and
because at that stage the cloud may not have come into equilibrium with its
environment. Comparing these temperatures to a temperature sonde taken from
nearby Manus Island at 0000 UTC on 28 January suggests a cloud altitude of
21-24 km. Tupper plotted the more conservative (smaller) value on figure 3.
The 27 January eruption cloud was extremely difficult to track, as it was
ice-rich and mixed with monsoonal storms, but dispersion models and
satellite analysis suggest that a mid-tropospheric portion spread quite
quickly W over Irian Jaya, while higher cloud remained near the eruption
site for some time. The best 'tracer' for the cloud in operations turned
out to be the strong 'ice' signature in split-window imagery¾similar to the
Hekla (Iceland) eruption in the year 2000.
Another large eruption occurred around 2300 on 28 January. That plume's
height plots at 18 km altitude (figure 3).
Preliminary synopsis. Tupper wrote that he and his group were aware of five
or six major events "during these [Manam] eruptions that have generated
high (over 10 km altitude) eruption clouds--23-24 October 2004, 31 October
2004, 10-11 November 2004, 23-24 November 2004, 19-20 December 2004, and
27-28 January 2005 [figure 3]. On each of these occasions a high and
sometimes persistent cloud has developed over a stronger phase of the
eruption. The largest event by far has been the 27-28 January event, which
was the only one to clearly penetrate into the stratosphere.
"Attached is a graph [figure 3] showing the heights reported by ground
observers, by local pilots, and derived from satellite analysis. Some major
differences of perspective are evident. I believe that, in general, the
ground observer heights are most accurate for the lower eruptions, pilot
reports can be accurate or quite inaccurate depending on the pilot and the
viewing angle, and satellite estimates are most accurate for the larger
eruptions.
"The cold-point tropopause generally occurs at around 16-18 km at this time
of year in Papua New Guinea, and scores of thunderstorms reach these
altitudes every day in the area. Consequently, it is not surprising that
the larger eruptions are easily able to reach these altitudes. The
tropopause is also the major dynamical limit on the rise of the larger
eruption clouds. The eruption of 27 January clearly penetrated into the
stratosphere, to altitudes of 21-24 km, based on the warmth of the central
umbrella cloud, and the subsequent dispersion of the ice-cloud, and the SO2
from the eruption."
"All of the eruption clouds have been water/ice rich, and difficult to
track using satellite techniques. The ash signal at altitudes above the
freezing level has been overwhelmed by the ice signal in infrared
split-window imagery. Similarly, in visible and true-colour imagery, even
where the lower level clouds have shown an ash signal, the higher clouds
have been a brilliant white and have only been revealed as volcanic in
short-wave infrared (3.7 um) imagery and with SO2 retrievals. For example,
[in Bulletin (v. 29, no. 11, the first of two satellite photos)] the large
brilliant white cloud to the N of Manam (overlying the dark ash cloud)
derives from the same 24 October eruption."
Background. The 10-km-wide island of Manam, lying 13 km off the northern
coast of mainland Papua New Guinea, is one of the country's most active
volcanoes. Four large radial valleys extend from the unvegetated summit of
the conical 1807-m-high basaltic-andesitic stratovolcano to its lower
flanks. These "avalanche valleys," regularly spaced 90 degrees apart,
channel lava flows and pyroclastic avalanches that have sometimes reached
the coast. Five small satellitic centers are located near the island's
shoreline on the northern, southern, and western sides. Two summit craters
are present; both are active, although most historical eruptions have
originated from the southern crater, concentrating eruptive products during
the past century into the SE avalanche valley. Frequent historical
eruptions have been recorded at Manam since 1616. A major eruption in 1919
produced pyroclastic flows that reached the coast, and in 1957-58
pyroclastic flows descended all four radial valleys. Lava flows reached the
sea in 1946-47 and 1958.
References: Tupper, A., and Kinoshita, K., 2003, Satellite, air and ground
observations of volcanic clouds over island of the Southwest Pacific: South
Pacific Study, v. 23, no. 2, p. 21-46.
Information Contacts: Andrew Tupper, Darwin Volcanic Ash Advisory Centre,
Australian Bureau of Meteorology (URL: www.bom.gov.au/info/vaac);
Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea;
National Disaster Centre, Department of Provincial Affairs and Local Level
Government (Ministry of Inter-Government Relations), PO Box 4970, Boroko,
National Capital District, Papua New Guinea (URL:
www.pngndc.gov.pg/); The National Online, Lot 13 Section 38, Waigani
Drive Hohola, PO Box 6817 Boroko, National Capital District, Papua New
Guinea (URL: www.thenational.com.pg/1206/); Papua New Guinea
Mapserver (Mapu), EDF 8/9 EU-SOPAC Reducing Vulnerability of Pacific ACP
States Project (see TikiMap map link at URL:
map.mineral.gov.pg/tiki/tiki-index.php David
Innes, Flight Safety Office, Air Niugini, P.O.Box 7186, Boroko, Port
Moresby, National Capital District, Papua New Guinea (Email:
dinnes@airniugini.com.pg or deejayinnes@yahoo.com, URL:
www.airniugini.com.pg/); Simon Carn, TOMS Volcanic Emissions Group,
University of Maryland, 1000 Hilltop Circle, Baltimore, MD 21250, USA
(Email: scarn@umbc.edu; URL: skye.gsfc.nasa.gov/).
Rinjani
Lesser Sunda Islands, Indonesia
8.42°S, 116.47°E; summit elev. 3,726 m
Rinjani had increases in some monitored parameters and hazard status during
this report interval, covering much of 2004 through 30 January 2005. An
eruption occurred on 1 October 2004. We previously presented a brief
aviation report concerning an unconfirmed ash cloud from Rinjani in
September 1995 (Bulletin v. 20, no. 10). In their text associated with
recent reporting used here, The Directorate of Volcanology and Geological
Hazard Mitigation (DVGHM) noted that Rinjani's last explosions occurred
during 4 June 1994-January 1995. Those explosions came from Barujari
volcano (see Background for morphologic information).
On 27 September 2004 a DVGHM report noted the decision to increase
Rinjani's hazard status to Alert Level II (Yellow, on a scale with the most
hazardous at IV). During the last third of 2004, the number of volcanic and
tectonic earthquakes had increased. Their increase followed a rise in the
number of tectonic earthquakes that began 18 August 2004. Tremor registered
on 23, 24, 25, and 26 September 2004. Tremor amplitudes ranged between 12
and 13.5 mm, and the duration of the tremor stood between 94 and 290 seconds.
At 0530 on 1 October 2004 Rinjani clearly erupted. The observation station
where visual monitoring occurs (Sembalun Lawang) lies in a spot where the
caldera wall blocks views into the active zone, so a smaller eruption might
have been missed. The eruption caused authorities to immediately raise the
hazard status to Alert Level III (Orange). Further details have not emerged
regarding the initial 1 October eruption. During the next few days of
eruptions, the lake Segara Anak remained undisturbed.
During 2-5 October 2004 continued explosions sent ash columns ~300 to 800 m
above the summit. Gray, thick ash columns drifted to the N. Detonation
sounds accompanied every explosion. Successive explosions occurred at
intervals of 5 to 160 minutes. Explosions vented on the NE slope of
Barujari volcano. Some material also vented from Barujari's peak, however,
and fell down around its edifice. A press report in the Jakarta Post
indicated that evacuations were not considered necessary.
Available monthly seismic data appears in table 2. Seismicity was dominated
by explosion earthquakes with maximum amplitudes of 30 mm. Explosion and
emission signals were common during February and March 2004 and became
absent or unreported after April 2004. Data were unavailable for October
2004 when known eruptions occurred.
Table 2. Available seismicity at Rinjani during 10 February 2004 to 30
January 2005. The symbol " - " means not reported. Courtesy of VSI.
Date Volcanic A Volcanic
B Tremor Emission Explosion
10 Feb 2004 2 -- 20 3 37
10 Mar 2004 3 3 16 5 32
10 Apr 2004 -- -- 5 -- 5
17-23 Jan 2005 20 28 11 -- --
24-30 Jan 2005 9 34 11 -- --
During 24 to 30 January 2005, gas plumes remained less than 600 m tall. The
tremor record had a maximum amplitude of 1.5 mm.
Background. Rinjani volcano sits on the island of Lombok and rises to 3,726
m, making it second in height among Indonesian volcanoes, only shorter than
Kerinci volcano (Sumatra). Rinjani has a steep-sided conical profile when
viewed from the E, but the W side of this compound volcano is truncated by
the oval-shaped (6 x 8.5 km) Segara Anak caldera. The caldera's western
half contains a 230-m-deep lake whose crescentic form results from growth
of the post-caldera cone Barujari (also written Baru Jari) at the caldera's
eastern end. Historical eruptions at Rinjani dating back to 1847 have been
restricted to Barujari cone and consist of moderate explosive activity and
occasional lava flows that have entered Segara Anak lake.
Information Contacts: Directorate of Volcanology and Geological Hazard
Mitigation (DVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (Email:
dali@vsi.dpe.go.id; URL: www.vsi.esdm.go.id/); The Jakarta Post,
Indonesia (URL: www.thejakartapost.com/).
Anatahan
Mariana Islands
16.35°N, 145.67°E; summit elev. 788 m
All times are local (= UTC + 10 hours)
As discussed in our previous report (Bulletin v. 29, no. 12), Anatahan's
third historical eruption began on 5 January 2005. Ongoing eruptions
continued through at least 18 February 2005.
Anatahan lies in the Commonwealth of the Northern Mariana Islands (CNMI)
~120 km N of Saipan and ~320 km N of Guam. The first historical eruption of
Anatahan began 10 May 2003 (Bulletin v. 28, nos. 4 and 5); after several
hours of increasing seismicity, a phreatomagmatic eruption sent ash to over
~9 km (~30,000 feet) and deposited about 10 million cubic meters of
material over the island and sea. A small craggy dome extruded in late May
and was destroyed during explosions on 13 and 14 June, after which the
eruption ceased. The second historical eruption began about 9 April 2004
after a week or so of increasing seismicity (Bulletin v. 29, no. 4). That
eruption primarily comprised Strombolian explosions every minute or so and
occasionally sent ash up to a few thousand feet. The eruption ended 26 July
2004.
Charles Holliday (US Airforce Weather Agency, AFWA) contributed a series of
remotely sensed images showing plumes in February (table 3, figure 6). The
plume in the 4 February Terra image (figure 6, top) contains a brownish
tinge suggesting considerable ash. The Anatahan region was on the western
edge of the Terra pass. The image contains an artifact reminiscent of
Venetian blinds (commonly called the bow-tie effect), which arose due to
pixel replication in the mapping/processing algorithm filling in for
missing data on the edge of the scan.
Table 3. A list of some of the satellite images recording Anatahan plumes
during 3-15 February 2005. Those shown with an asterisk appear in the next
figure. Date and time are both UTC; for example, 04 Feb 2005 @ 0105 is the
date and time in UTC, in this example equivalent to 04 Feb 2005 at 1105
local time. Names affiliated with satellites are as follows: DMSP (Defense
Meteorological Satellite Program), NOAA (National Oceanic and Atmospheric
Administration), NASA (National Aeronautics and Space
Administration). Courtesy of Charles Holliday, U.S. Air Force Weather Agency.
2005 Time Satellite and type of image
(UTC) Predominant direction of plume and comments
03 Feb 2329 DMSP F16 (capturing visible data at 0.3 nanometer
(nm) wavelength)
Steam and vog; seen at least 95 NM (~180 km) from
Anatahan, trending
slightly E of S.
04 Feb *0105 NASA TERRA MODIS (250 m resolution)
Steam and vog; seen for at least 100 NM (~185 km) to
the S.
06 Feb 0050 NASA TERRA MODIS (500 m resolution)
Steam and vog; 100 NM (~185 km) trending to WSW.
06 Feb 0043 NOAA 17 (visible, 0.5 nm wavelength)
Steam and vog; 175 NM (~320 km) to SW.
06 Feb 0335 NASA AQUA MODIS (500 m resolution)
Steam and vog; 150 NM (~280 km) trending to WSW.
08 Feb 2226 DMSP F15 (visible, 0.3 nm)
Steam and vog; 150 NM (~280 km) trending to SW.
09 Feb 0125 NASA TERRA MODIS (500 m resolution)
Steam and vog to the SSW; plume length undisclosed.
09 Feb 0442 NOAA 16 (visible, 0.5 nm and infrared (IR), 0.5 nm)
Steam and vog; 150 NM (~280 km) trending over a
sector from SW to WSW.
09 Feb 2207 DMSP F16 (visible, 0.5 nm)
Ash and steam for ten's of kilometers; vog at
greater distances, up to at
least 130 NM (240 km) WSW.
10 Feb 0030 NASA TERRA MODIS (250 m resolution)
Ash and steam nearer volcano, blowing S to SSW;
region interpreted as vog
at distances of ten's of kilometers SW of volcano.
10 Feb 0052 NOAA 17 (0.5 nm)
Vog visible 220 NM (~410 km) to the WSW.
10 Feb 0330 NASA AQUA MODIS (500 m resolution)
Ash and steam nearer volcano, blowing SW; vog at
distances ~150 NM (~280
km) WSW of volcano.
10 Feb 0423 NOAA 16 (IR, 0.5 nm)
Ash and steam; plume blown 100 NM (185 km) to W and WSW.
10 Feb 0423 NOAA 16 (visible, 0.5 nm)
Ash and steam; 475 NM (967 km) trending to WSW.
10 Feb 2251 DMSP F15 (visible, 0.3 nm)
Ash and steam for ten's of kilometers WSW from
Anatahan; vog at greater
distances visible up to at least 475 NM (967 km)
from the volcano.
11 Feb 0110 NASA TERRA MODIS (1 km resolution)
One of the longer-extended plumes identified in this
set, trending SW and
reaching 525 NM (~972 km) from source to
identified vog near the SW
corner of the image. Ash and steam to ten's of
kilometers from source.
11 Feb 0412 NOAA 16 (0.5 nm)
Ash and steam plume that gradually broadens as it
drifts WSW. The plume was
ultimately identified as vog in the more distal
areas. Total length
identified 505 NM (936 km).
11 Feb 0415 NASA AQUA MODIS (500 m resolution)
Plume clearer than on most other images in this set,
with few weather
clouds obscuring; SW-directed plume identified as
ash and steam near
source; vog in distal areas to ~150 NM (~280 km).
11 Feb 0702 GOES-9 (visible)
Longest-extending plume of this set; ash and steam
WSW of volcano; vog
detected at 850 NM (~1,600 km) from Anatahan.
12 Feb 0401 NOAA 16 (visible, 0.3 nm)
W-directed plume with ash/steam near source, vog at
355 NM (657 km).
12 Feb 2316 DMSP F16 (visible, 0.3 nm)
SW-directed plume, ~140 NM long (~260 km).
13 Feb 0100 NASA TERRA MODIS (500m resolution)
SW-directed plume, ~200 NM (~370 km) long.
13 Feb 0124 NOAA 17 (visible, 0.5 nm)
W-directed plume, ~360 NM long (~670 km).
13 Feb 1229 NOAA 17 IR (0.5 nm)
WNW-directed plume, 95 NM (180 km) long.
13 Feb *2303 DMSP F16 (visible, 0.3 nm)
SW-directed plume, ash and steam for much of 140 NM
(260 km) length
(unusually clear conditions).
14 Feb 0101 NOAA 17 IR (0.5 nm)
Elongate ash-and-steam plume stretched SW to ~120 NM
(~220 km).
14 Feb 0101 NOAA 17 (visible, 0.5 nm)
Ash and steam plume(s) near source; vog visible on
image to over 400 NM
(740 km).
14 Feb 0305 NASA AQUA MODIS (250m resolution)
SSW-directed plume with ash and steam, but length
undisclosed.
14 Feb 0519 NOAA 16 (visible, 0.5 nm)
W-directed ash-and-steam plume in the near source,
vog seen ~500 NM
(~930 km) to the W.
15 Feb 0038 NOAA 17 (visible, 0.5 nm)
Gravity waves to the W for 25 NM (~45 km); faint vog
seen to ~80 km
(~150 km).
15 Feb 0045 NASA TERRA MODIS (500 m resolution)
(Similar to above)
15 Feb 0350 NASA TERRA MODIS (1 km resolution)
Ash and steam ~350 NM to the W to SW; faint vog in
more distal areas.
15 Feb 0507 NOAA 16 (visible, 0.5 nm)
Plume directed WSW stretching 345 NM (640 km).
15 Feb 0812 NOAA 15 (IR, 0.5 nm)
Ash and steam directed WSW stretching 175 NM (326 km).
Figure 6. Two remotely sensed images of Anatahan plumes during February
2004 (N is upwards). (top) S-blown steam and vog on 4 February at 0105 UTC
clearly identifiable to Saipan and Tinian islands; reported as the source
of health problems in Guam news reports (see text). (bottom) A modest
ash/steam plume in unusually clear conditions, imaged at 2303 UTC on 13
February (DMSP F16 visible) reached 260 km (140 NM). Courtesy of Charles
Holliday, U.S. Air Force Weather Agency.
Randy White of the U.S. Geological Survey noted that the energy release
from seismic stations monitoring Anatahan dropped to near zero on 13
February 2005, yet a monitoring microphone continued to indicate
considerable acoustic-energy release. Corresponding to this, a MODIS image
clearly showed ash still being emitted early on 14 February (see table 3).
In other words, the seismicity failed to accurately portray the eruption's
vigor.
Reporters Katie Worth and Natalie Quinata wrote in the 5 February 2004
issue of the Pacific Daily News that many students in school on Guam had
been sent home after experiencing dizziness or nausea because of the
foul-smelling 'vog' or volcanic smog hovering over the island from the
eruption. Guam lies ~320 km S of Anatahan.
John Ravelo wrote a news article for the Saipan Tribune published on 15
February with the title "Anatahan ash cloud continues to hinder flights."
Ravelo said that, "An aircraft coming from Manila to Saipan experienced
zero visibility before landing at the Francisco C. Ada-Saipan International
Airport yesterday morning, prompting the carrier's pilots to fly around the
island and search for a clearer approach to the runway. The passenger
aircraft landed safely at the airport, but the hazy condition delayed its
arrival."
At about 0909 on 14 February, the Washington Volcanic Ash Advisory Center
(VAAC) reported that a plume of ash extended SW of the volcano at an
altitude of 4.3 km. The plume was 18-28 km wide. Later in the afternoon,
the Washington VAAC reported an ash plume below an altitude of 2.7 km that
extended SW of the volcano for about 460 km. The VAAC also forecasted that
the plume would shift to a more westerly direction within the next 12 hours.
According to Ravelo's 15 February Saipan Tribune article, the CNMI
Emergency Management Office and the U.S. Geological Survey "said in a joint
report that the magnitude of the volcanic eruption declined during the past
few days." During the eruption's peak on 26 January and 1 February 2005,
however, the article stated that both agencies noted that the volcano sent
ash to about 4.6-6.1 km altitude.
A message from Holliday filed at 0100 UTC on 17 February 2005 included a
series of remarks, mainly from unnamed scientists on the scene in the
field. As background prior to presenting those remarks, we note that the
term 'RSAM' (real-time seismic amplitude) signifies estimates the average
amplitude of ground shaking. RSAM values increase with increases in tremor
amplitude or the rate of occurrence and size of earthquakes. The RSAM
estimates the seismicity during intervals when many earthquakes might
occur, times when rapid earthquake-magnitude assessments might become
impractical. The remarks follow.
"Over the past 24 hours, the eruptive activity at Anatahan apparently
continued to decline, with RSAM levels at the seismic station ANAT now only
marginally above the levels recorded just before the 5 January eruption
began. Microphone amplitudes have also dropped to similar levels.
"The 2003 crater floor is now essentially entirely covered by fresh lava
[with] a diameter of about one kilometer. The current eruption peaked
during the period between 26 January and 2 February [2005], during which
the volcano sent ash as high as 15,000 to 20,000 feet a.s.l. [~5,000 to
~6,000 m] . . .. In the days following, ash blew as far as 100 nautical
miles [185 km] and vog blew nearly 600 [nautical] miles [~1,100 km] downwind.
"The third historical eruption of Anatahan began on 5 January, after three
days of precursory seismicity. On 6 January frequent strombolian explosion
signals began and by the next day ash was rising to 10,000 feet [~3 km] and
blowing 40 nautical miles [72 km] downwind. Bombs a meter in diameter were
being thrown hundreds of feet in the air [ 1 foot = 0.305 m]. By January 20
explosions were occurring every 3 to 10 seconds and fresh ejecta and small
lava flows had filled the innermost crater to nearly the level of the
pre-2003 East Crater floor.
"The Emergency Management Office, Office of the Governor, CNMI, has placed
Anatahan Island off limits until further notice and concludes that,
although the volcano is not currently dangerous to most aircraft within the
CNMI airspace, conditions may change rapidly, and aircraft should pass
upwind of Anatahan or beyond 30 km downwind from the island and exercise
due caution within 30 km of Anatahan."
Background. The elongated, 9-km-long island of Anatahan in the central
Mariana Islands consists of two coalescing volcanoes with a 2.3 x 5 km,
E-trending summit depression formed by overlapping summit calderas. The
larger western caldera is 2.3 x 3 km wide and extends eastward from the
summit of the western volcano, the island's 788-m-high point. Ponded lava
flows overlain by pyroclastic deposits fill the caldera floor, whose SW
side is cut by a fresh-looking smaller crater. The summit of the lower
eastern cone is cut by a 2-km-wide caldera with a steep-walled inner crater
whose floor is only 68 m above sea level. Sparseness of vegetation on the
most recent lava flows on Anatahan indicated that they were of Holocene
age, but the first historical eruption of Anatahan did not occur until May
2003, when a large explosive eruption took place forming a new crater
inside the eastern caldera.
Information Contacts. Charles Holliday, U.S. Air Force Weather Agency
(AFWA), Offutt Air Force Base, Nebraska 68113, USA (Email:
Charles.Holliday@afwa.af.mil); Randy White, U.S. Geological Survey, 345
Middlefield Road, Menlo Park, CA 94025-3591 USA (Email: rwhite@usgs.gov);
Katie Worth and Natalie Quinata, Guam Pacific Daily News, P.O. Box DN,
Hagatna, Guam 96932, USA (URL: www.guampdn.com/, Email:
kworth@guampdn.com); John Ravelo, Saipan Tribune (15 February 2005), PMB
34, Box 10001, Saipan, MP 96950, USA (URL: www.saipantribune.com/);
Operational Significant Event Imagery (OSEI) team, World Weather Bldg.,
5200 Auth Rd Rm 510 (E/SP 22), NOAA/NESDIS, Camp Springs, MD 20748, USA
(URL: www.osei.noaa.gov/, Email: osei@noaa.gov); Washington Volcanic
Ash Advisory Center (VAAC), Satellite Analysis Branch, NOAA/NESDIS E/SP23,
NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746 USA
(URL: www.ssd.noaa.gov/).
Asama
Honshu, Japan
36.40°N, 138.53°E; summit elev. 2,560 m
All times are local (= UTC + 9 hours)
Setsuya Nakada and Yukio Hayakawa provided follow-up information on events
at Asama since our last report (Bulletin v. 30, no. 1). Asama's largest
recent explosion occurred on 1 September 2004, and the second largest, on
14 November 2004. Subsequent eruptions have been absent except for a small
one in early December 2004.
The eruption that started on 1 September 2004 was characterized by an
increase in the number of A-type earthquakes occurring during and after the
main phase of explosions (based on data collected by the University of
Tokyo's Earthquake Research Institute (ERI) and the Japan Meteorological
Agency). Deep seismicity peaked at the end of 2004, but had subsequently
remained moderate. GPS (global positioning system) instruments maintained
ERI and the Geographical Survey Institute (GSI) disclosed inflation of the
edifice. This inflationary trend has continued since mid-October 2004.
ERI undertook detailed analysis of earthquake hypocenters and the pressure
source for the observed GPS data. This showed the existence of a
dike-shaped magma reservoir trending WNW-ESE. The reservoir occurred just W
of the summit and 1-2 km below sea level.
Around October 2004 the height of the lava filling the summit crater
reached a maximum. Around that time the dome attained a height just ~70 m
below the crater's lowest notch (an opening along the N rim). By the end of
January 2005, in contrast, the center of the lava pool had deepened,
possibly due to draining of the lava body back into the conduit.
A sequence of radar images provided glimpses into changeable features
inside the steamy crater. Two images appear here, from 16 September and 15
December 2004 (figures 7 and 8). The former shows a flat-looking
disk-shaped extrusion in the crater. The latter shows that the earlier
extrusion had by this time become disrupted or perhaps buried.
Figure 7. Radar image of Asama's summit crater taken from a Cessna airplane
on 16 September 2004 by the Geographical Survey Institute, Japan. N is up.
Radiated microwaves were transmitted from the N, at 4,290 m altitude, 2 km
from the crater, with the off-nadir angle of 55 degrees. Courtesy of the
Geographical Survey Institute.
Figure 8. Radar image of Asama's summit crater taken from a Cessna on 15
December 2004 by the Geographical Survey Institute, Japan. N is up.
Radiated microwaves were transmitted from the N, 2 km from the crater, with
the off-nadir angle of 55 degrees. Courtesy of Geographical Survey Institute.
Strong glowing at the summit was considered to be due to significant
degassing after the main explosive phase. SO2 flux peaked around October
(at ~5,000 metric tons a day) and has continued at a relatively high level,
as much as 2,000 to 3,000 metric tons a day.
The eruptions emitted andesite (SiO2 ~61%), with high crystallinity, and
containing partially melted sedimentary and other rock (felsic tuff?). The
rock chemistry has remained uniform throughout the eruptions of the past
several thousand years, though the inclusion of melted sedimentary rock was
absent in products erupted prior to 2004.
Yukio Hayakawa provided a composite isomass map of 2004 Asama tephra
deposits (figure 9). By far the largest deposit of the year erupted on 1
September. The smallest documented deposit occurred on 10 October. Ash
deposits from activity on 1 September drifted NE, deposits from 16
September drifted SSE; 23 September, NNE; 29 September, N; 10 October, NE;
and 14 November, E.
Figure 9. Isomass map of 2004 Asama tephra deposits erupted during
September-November 2004. Open circles indicate cities; dots indicate
sampling points where g/m2 of ash were measured; contours are in the same
units. Courtesy Yukio Hayakawa.
Background. Asama, Honshu's most active volcano, overlooks the resort town
of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of
the Izu-Marianas and NE Japan volcanic arcs. The modern cone of
Maekake-yama forms the summit of the volcano and is situated east of the
horseshoe-shaped remnant of an older andesitic volcano, Kurofu-yama, which
was destroyed by a late-Pleistocene landslide about 20,000 years before
present (BP). Growth of a dacitic shield volcano was accompanied by
pumiceous pyroclastic flows, the largest of which occurred about
14,000-11,000 years BP, and by growth of the Ko-Asama-yama lava dome on the
east flank. Maekake-yama, capped by the Kama-yama pyroclastic cone that
forms the present summit of the volcano, is probably only a few thousand
years old and has an historical record dating back at least to the 11th
century AD. Maekake-yama has had several major plinian eruptions, the last
two of which occurred in 1108 and 1783 AD.
Information contacts: Setsuya Nakada, Volcano Research Center, Earthquake
Research Institute (ERI), University of Tokyo, Yayoi 1-1-1, Bunkyo-ku,
Tokyo 113, Japan (Email: nakada@eri.u-tokyo.ac.jp; URL:
www.eri.u-tokyo.ac.jp/topics/...e.html); Yukio
Hayakawa, Faculty of Education, Gunma University, Aramaki 4-2, Maebashi
Gunma 371-8510, Japan (Email: hayakawa@edu.gunma-u.ac.jp, URL:
maechan.net/hayakawa/asama/gankoran/,
www.edu.gunma-u.ac.jp/~hayaka...h.html); Geographical Survey
Institute, Ministry of Land, Infrastructure and Transport, 1, Kitasato,
Tsukuba-shi, Ibaraki-ken 305-0811 Japan (URL: www.gsi.go.jp; URL
with radar data (text in Japanese): www.gsi.go.jp/BOUSAI/ASAMA/);
Japan Meteorological Agency, Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122,
JAPAN (URL: www.jma.go.jp/ ).
Shiveluch
Kamchatka Peninsula, Russia
56.653 N, 161.360 E; summit elev. 3,283 m
All times are local (= UTC + 12 hours [+13 hours in March-June])
The previous report on Shiveluch (Bulletin v. 29, no. 5) covered activity
until 27 May 2004. From May 2004 until September 2004, seismicity at
Shiveluch was above background, with many shallow earthquakes recorded 0-5
km beneath the active lava dome, and Shiveluch remained at Concern Color
Code Orange. Periods of continuous spasmodic tremor were recorded in May,
June, July, and October 2004. Gas-and-steam plumes rising to 3-6 km
altitude were frequent, sometimes drifting up to 10 km or more. A small
lava flow on top of the active dome, first observed on 21 May, continued to
flow until 28 May. On 19 June, a likely ash cloud was seen 10-20 km S of
the volcano. The lava dome continued to grow in Shiveluch's active crater.
On 6 September at 2054 an explosion produced small pyroclastic flows and an
ash plume that rose to ~5.5 km altitude. According to satellite data, 1- to
12-pixel thermal anomalies were registered over the lava dome on 15-16
September 2004. During 23-29 September, 26 strong shallow earthquakes up to
M 2.3 were recorded. An explosion on 25 September was accompanied by small
pyroclastic flows. The Kamchatka Volcanic Eruptions Response Team
(KVERT),again reported seeing a new lava flow at Shiveluch's lava dome
around 26 October.
Based on interpretations of seismic data, possible ash-and-gas explosions
up to 7 km altitude occurred throughout October (figure 10), November, and
December 2004. Possible minor ash-and-gas explosions and hot avalanches
also occurred. On 28 December a gas-and-steam plume extended as far as 50 km E.
Figure 10. A dark plume of ash streamed from the Shiveluch at 0110 UTC on
20 October 2004, when the Moderate Resolution Imaging Spectroradiometer
(MODIS) on NASA's Terra satellite captured this image. MODIS observed
several such plumes in October. Fainter plume(s) to the SW can be seen from
Bezymianny or Kliuchevskoi, both of which were emitting ash plumes during
the first week of October.
During January and February 2005, seismicity decreased slightly at
Shiveluch but remained above background levels, with weak shallow
earthquakes occurring beneath the active dome. Possible weak ash-and-gas
explosions and hot avalanches occurred throughout January and February, and
gas-and-steam plumes rose up to 2-7 km altitude.
On 13 January, several ash explosions up to 5 km altitude and a pyroclastic
flow probably occurred. The Tokyo Volcanic Ash Advisory Center (VAAC)
reported an eruption of Shiveluch on 17 January at 1625 with a plume that
rose to a height of ~4.5 km altitude. On 6 February a pyroclastic flow
traveled ~2 km down the volcano's flank. On 17 February ash deposits were
seen on the volcano's snow-covered lava dome extending to the SE and S.
A large eruption occurred at Shiveluch from 1825 on 27 February to 0100 on
28 February, leading KVERT to raise the Concern Color Code from Orange to
Red (the highest level). Meteorological clouds obscured the volcano during
the eruption. According to satellite data (NOAA 16 at 1656 UTC on 27
February), a 45-pixel thermal anomaly was registered near the dome (band
3). This anomaly was probably related to a large pyroclastic flow on the SW
flank. At this time analysts detected a 45-km-long ash cloud on satellite
imagery trending NW of the volcano. At 0900 on the 28th, ash deposits were
noted in the town of Klyuchi, ~46 km from the volcano. Satellite imagery
from 1205 on 28 February showed ash deposits W of Shiveluch covering an
area of 24,800 km^2. Later that day, an ash cloud extending more than 360
km was centered over the western half of Kamchatka. On 1 March the Concern
Color Code was reduced to Orange. Prior to the 27 February eruption,
seismicity was above background levels and ash-and-gas plumes were seen on
video rising to ~3 km above the lava dome.
Explosions deposited ash in Ust'-Hairyuzovo village, about 250 km to the W,
on 27 and 28 February, and on 2 March. The seismic station at Shiveluch
stopped working on 27 February. According to visual and video data on 2
March, part of a large pyroclastic flow was observed on the SW flank of the
volcano. According to satellite data from the USA and Russia, a 2- to
23-pixel thermal anomaly was registered at the dome on 1-3 March. Clouds
obscured the volcano at other times. Shiveluch remained at Concern Color
Code Orange.
Background. The high, isolated massif of Shiveluch volcano (also spelled
Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group.
The 1,300 km^3 Shiveluch is one of Kamchatka's largest and most active
volcanic structures. The summit of roughly 65,000-year-old Strary Shiveluch
is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the
S. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome
complex was constructed during the Holocene within the large
horseshoe-shaped caldera; Holocene lava dome extrusion also took place on
the flanks of Strary Shiveluch. At least 60 large eruptions of Shiveluch
have occurred during the Holocene, making it the most vigorous andesitic
volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these
eruptions have provided valuable time markers for dating volcanic events in
Kamchatka. Frequent collapses of dome complexes, most recently in 1964,
have produced debris avalanches whose deposits cover much of the floor of
the breached caldera.
Information Contacts: Olga A. Girina, Kamchatka Volcanic Eruptions Response
Team (KVERT), a cooperative program of the Institute of Volcanic Geology
and Geochemistry, Far East Division, Russian Academy of Sciences, Piip Ave.
9, Petropavlovsk-Kamchatskii 683006, Russia (Email: girina@kcs.iks.ru), the
Kamchatka Experimental and Methodical Seismological Department (KEMSD), GS
RAS (Russia), and the Alaska Volcano Observatory (USA); Alaska Volcano
Observatory (AVO), a cooperative program of the U.S. Geological Survey,
4200 University Drive, Anchorage, AK 99508-4667, USA (URL:
www.avo.alaska.edu/; Email: tlmurray@ usgs.gov), the Geophysical
Institute, University of Alaska, P.O. Box 757320, Fairbanks, AK 99775-7320,
USA (Email: eisch@dino.gi.alaska.edu), and the Alaska Division of
Geological and Geophysical Surveys, 794 University Ave., Suite 200,
Fairbanks, AK 99709, USA (Email: cnye@giseis.alaska.edu); Tokyo Volcanic
Ash Advisory Center, Tokyo Aviation Weather Service Center, Haneda Airport
3-3-1, Ota-ku, Tokyo 144-0041, Japan
(www.jma.go.jp/JMA_HP/jma/...index.html).
Veniaminof
Alaska Peninsula, USA
56.17°N, 159.38°W; summit elev. 2,507 m
All times are local = UTC - 9 / 8 hours (winter / summer)
After a long period of quiescence, Veniaminof began exhibiting increased
seismicity and possible low-level eruptive activity from September 2002
through mid-April 2003. Between mid-April 2003 and February 2004 no signs
of activity were observed. From February 2004 until the end of June 2004
steam and ash emissions were observed and volcanic tremor and earthquakes
recorded (Bulletin v. 29, no. 6).
Activity during July 2004. Throughout July 2004 short intervals of volcanic
tremor continued. Small amounts of dark ash were seen in the ice-filled
caldera on 27 June. During the second week of July, the Alaska Volcano
Observatory (AVO) reported that the tremor correlated well with
ash-and-steam plumes as high as 1.5 km altitude; during the rest of the
month, these plumes may have reached as high as 3.7 km altitude. On 22 July
at 1229, an AVO field crew witnessed a small ash burst rise a few hundred
meters above the summit of the intracaldera cone (figure 11). This type of
activity had prevailed at Veniaminof during the previous three months.
During the last week of July, the cone produced variable amounts of white
steam from at least two separate craters near its top. The snow-and-ice
field over much of the caldera was covered with a discontinuous, 1- to 2-mm
thick ash blanket. No visual observations of ash emissions were made after
22 July, although the recorded seismicity was similar to that observed
during ash emissions in the previous few months. Veniaminof remained at
Concern Color Code Yellow throughout July.
Figure 11. Veniaminof's intracaldera cone photographed on 22 July 2004 in a
view to the SW. The ~330-m-high intracaldera cinder and spatter cone was
the source of all known historical Veniaminof eruptions. The cone protrudes
through glacial ice that fills the summit caldera. Although this photo was
taken during an interval with occasional minor ash and steam emissions, at
this moment only steam rises to a few hundred meters above the cone. A very
faint dusting of ash has discolored the glacier's surface; however, some
may be older, wind-blown ash rather than freshly erupted ash. Courtesy of
K.L. Wallace, USGS.
Activity during August 2004. Episodes of volcanic tremor continued
throughout August. No visual observations of ash emissions were made from
22 July through the first week of August, although the recorded seismicity
was similar to that observed during ash emissions in the previous weeks.
Throughout the month, frequent small ash-and-steam emissions from
Veniaminof were visible on the web camera in Perryville and confirmed by
AVO geologists working in the area. Bursts of volcanic tremor recorded
intermittently on 17 August were probably associated with low-level,
short-term ash emissions. Veniaminof remained at Concern Color Code Yellow
throughout August 2004.
Activity during September 2004. During the first three weeks of September
both low-level tremor and intermittent bursts of tremor continued at
Veniaminof. AVO scientists believed tremor episodes likely represented
low-level ash-and-steam emissions similar to those observed during the
previous two months. Minor emissions of ash and steam were occasionally
seen on the web camera during clear weather. During the last week of
September, low-level tremor and intermittent small tremor bursts may have
occurred at Veniaminof, but high winds in the area caused considerable
vibrational noise, masking the signal of interest, and making analysis of
seismic records inconclusive. The winds were strong enough to hide evidence
of low-level tremor. If the tremor episodes continued, they likely
corresponded with low-level ash-and-steam emissions similar to those
observed over the previous four months. Cloudy conditions obscured views of
the volcano by web camera and satellite. Veniaminof remained at Concern
Color Code Yellow throughout September.
Activity during October 2004. Low-level seismic tremor and intermittent
small tremor bursts continued. These tremor episodes likely represented
low-level ash and steam emissions similar to those observed over the past
four months, although cloudy conditions obscured views of the volcano by
web camera and satellite.
Low-level tremor during 8-15 October correlated with weak steaming of the
intracaldera cone as observed on the web camera. No ash emissions were
observed, although cloudy conditions over the caldera restricted viewing
for much of the week. AVO lowered the Concern Color Code at Veniaminof on
26 October from Yellow to Green. Seismicity, which had been associated with
ash emissions during the summer of 2004, decreased to levels that indicated
ash, ash-and-steam, or steam emissions were no longer occurring on a
regular basis. Since early September, no ash emissions were seen on the web
camera and no evidence of ash was visible on satellite imagery. Also, AVO
had received no recent reports of ash from pilots or ground observers. AVO
considered the intermittent, low-level seismic tremor that continued to be
recorded at the volcano to be part of the background activity.
Activity during January 2005. AVO raised the Concern Color Code at
Veniaminof from Green to Yellow on 4 January because around that time
several small ash emissions from the volcano's intracaldera cone were
observed on the web camera in Perryville. Ash emissions were visible
starting around 0938, but may have been obscured by meteorological clouds
in previous images. The discrete ash emissions were small, rose hundreds of
meters above the cone, and dissipated as they drifted E. Minor ash fall was
probably confined to the summit caldera. Very weak seismic tremor was
recorded beginning on 1 January, and increased slightly over the next 2
days. These seismic signals were similar to those recorded during
steam-and-ash emissions in April to October 2004. However, there were no
indications from seismic data that events significantly larger than those
observed around 4 January were imminent.
AVO raised the Concern Color Code at Veniaminof from Yellow to Orange on 10
January as ash emissions from the volcano's intracaldera cone reached
heights of nearly 4 km during 8-10 January (figure 12). Seismicity remained
at elevated levels and satellite images showed a persistent thermal anomaly
at the intracaldera cone. On 11 January, the Anchorage VAAC again reported
emission of a thin ash cloud to ~3 km altitude visible on the Perryville
web camera. On 12 January the Anchorage VAAC reported emission of a thin
ash cloud, visible on the Perryville web camera, that rose to 3-4 km
altitude, extended ENE, and dissipated within ~55 km of the volcano. On 14
January, a satellite image showed a thermal anomaly in the vicinity of the
Veniaminof summit. Although the anomaly appeared less intense than when
first detected on 8 January and volcanism seemed to have declined
significantly since 12 January, activity still remained significantly
higher than normal with occasional bursts of volcanic tremor.
Figure 12. Veniaminof intracaldera cinder cone, 11 January 2005. The
elevation of the cone is 2,156 m and the ash plume is drifting to NE. Photo
taken during an observational overflight. Image courtesy of K.L.Wallace, USGS.
During the rest of the month of January, seismic data, web camera views,
and satellite images indicated that low-level ash emissions continued at
Veniaminof. Seismicity was similar to levels observed during the previous
week, consisting of low-amplitude volcanic tremor with occasional larger
bursts. During clear weather, satellite imagery showed anomalous heat at
the summit cone, consistent with hot blocks and ash being ejected from the
active vent. In addition, the web camera showed intermittent ash plumes
reaching as high as 3 km altitude. Occasional stronger bursts of seismic
tremor during 20-21 January and around 28 January may have indicated plumes
to higher levels, but not above 4 km altitude. Veniaminof remained at
Concern Color Code Orange.
Activity during February 2005. On the evening of 3 February, Strombolian
activity at Veniaminof was visible by residents of Perryville ~30 km from
the volcano. Activity was also observed on web camera views and seen by
satellite as an increase in radiated surface heat. An increase in
seismicity suggested that Strombolian activity may have continued through 4
February while the volcano was obscured by clouds.
During 28 January to 4 February, seismicity at Veniaminof was similar to
levels for the previous week, with low-amplitude tremor and occasional
larger bursts. During clear weather, satellite imagery showed anomalous
heat at the summit cone, consistent with hot blocks and ash being ejected
from the active vent. The web camera showed intermittent ash plumes
reaching as high as 3 km altitude. Veniaminof remained at Concern Color
Code Orange.
Low-level Strombolian eruptive activity continued at Veniaminof during 4-11
February. On 9 February, an ash burst rose hundreds of meters above the
intracaldera cone. Satellite images continued to show a thermal anomaly in
the vicinity of the intracaldera cone, consistent with the presence of hot
material at the vent. Seismicity remained above background levels at the
volcano. On the morning of 10 February there was a distinct increase in the
amplitude and frequency of earthquakes. The increase continued through 11
February. This activity was consistent with more energetic explosions from
the active cone, but there were no indications that the bursts rose higher
than 4 km altitude. Veniaminof remained at Concern Color Code Orange.
During 11-18 February, it was likely that low-level Strombolian eruptive
activity continued at Veniaminof based on seismic data and satellite
imagery. Cloudy conditions obscured web camera views of the volcano, and no
ash emissions were observed above the cloud cover. Seismicity remained
above background levels at Veniaminof. The character of the seismicity
changed slightly during the report period, with frequent periods of
continuous banded volcanic tremor occurring, but the amplitudes of
earthquakes did not increase. This activity was consistent with explosions
from the active cone; however, there was no indication that these bursts
rose more than 4 km altitude. Veniaminof remained at Concern Color Code Orange.
Seismicity decreased substantially at Veniaminof during 18-25 February in
comparison to previous weeks, leading AVO to decrease the Concern Color
Code from Orange to Yellow. Periods of volcanic tremor diminished, and no
discrete events associated with ash bursts had occurred for several days.
Only minor steam emissions were seen. AVO received no reports of ash
emissions from pilots or ground observers. AVO concluded that given the
decline in seismicity, it appeared that the most recent episode of
Strombolian eruptive activity at Veniaminof had ended.
Activity during March 2005. A further reduction in activity at Veniaminof
during 25 February to 4 March led AVO to reduce the Concern Color Code from
Yellow to Green, the lowest level. For more than a week seismic activity
was at background levels, periods of volcanic tremor had ceased, and there
were no discrete events associated with ash bursts. Only minor emissions of
steam were observed on the web camera and satellite imagery. AVO received
no reports of ash emissions from pilots or observers on the ground. They
concluded that given the decline in seismicity it appeared that the most
recent episode of eruptive activity had ended at Veniaminof.
Background. Massive Veniaminof volcano, one of the highest and largest
volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11
km, glacier-filled caldera that formed around 3,700 years ago. The caldera
rim is up to 520 m high on the N, is deeply notched on the W by Cone
Glacier, and is covered by an ice sheet on the S. Post-caldera vents are
located along a NW-SE zone bisecting the caldera. That zone extends 55 km
from near the Bering Sea, across the caldera, and down the Pacific flank.
Historical eruptions probably all originated from the westernmost and more
prominent of two intra-caldera cones, which reaches an elevation of 2,156 m
and rises about 300 m above the surrounding icefield. The other cone is
larger, and has a summit crater or caldera that may reach 2.5 km in
diameter, but is more subdued and barely rises above the glacier surface.
Information Contacts: Alaska Volcano Observatory (AVO), a cooperative
program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK
99508-4667, USA (URL: www.avo.alaska.edu/; Email:
tlmurray@usgs.gov), b) Geophysical Institute, Univ. of Alaska, P.O. Box
757320, Fairbanks, AK 99775-7320, USA (Email: eich@dino.gi.alaska.edu), and
c) Alaska Division of Geological & Geophysical Surveys, 794 University
Ave., Suite 200, Fairbanks, AK 99709, USA (Email: cnye@giseis.alaska.edu);
Kristi L. Wallace, USGS/AVO, Alaska Tephra Laboratory and Data Center, 4230
University Drive, Suite 201, Anchorage, AK 99508, USA (Email:
kwallace@usgs.gov).
St. Helens
Washington, USA
46.20°N, 122.18°W; summit elev. 2,549 m
All times are local ( = UTC - 8 hours)
Growth of the new lava dome inside the crater of Mount St. Helens has
continued since the last report (Bulletin v. 29, no. 10), accompanied by
low rates of seismicity, low emissions of steam and volcanic gases, and
minor production of ash. During such eruptions, episodic changes in the
level of activity can occur over days to months. The eruption can also
intensify suddenly or with little warning and produce explosions that may
cause hazardous conditions within several kilometers of the crater and
farther downwind. The current status is Volcano Advisory (Alert Level 2),
and the aviation color code is orange.
A small, short-lived explosive event at St. Helens volcano began at
approximately 1725 hours on 8 March 2005. Airplane pilot reports indicated
that the resulting steam-and-ash plume reached an altitude of about 11 km
above sea level within a few minutes and drifted NE.
Results from analysis of imagery by the U.S. Geological Survey of 21
February 2005 showed that the highest part of the new lava dome stands at
an altitude of 2.3 km, 160 m higher than the old lava dome, and only 28 m
below Shoestring Notch, a low point on the SE crater rim. Further analysis
of recent aerial photos revealed that as of 1 February, the
whaleback-shaped dome extrusion was about 470 m long and 150 m wide. The
new dome and uplifted welt of crater floor and deformed glacier ice have
grown to a combined volume of about 38 million m3, almost one-half the
volume of the old lava dome.
Background. Prior to 1980, Mount St. Helens formed a conical, youthful
volcano sometimes known as the Fuji-san of America. During the 1980
eruption the upper 400 m of the summit was removed by slope failure,
leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava
dome. Mount St. Helens was formed during nine eruptive periods beginning
about 40-50,000 years ago and has been the most active volcano in the
Cascade Range during the Holocene. Prior to 2,200 years ago, tephra, lava
domes, and pyroclastic flows were erupted, forming the older St. Helens
edifice, but few lava flows extended beyond the base of the volcano. The
modern edifice was constructed during the last 2,200 years, when the
volcano produced basaltic as well as andesitic and dacitic products from
summit and flank vents. Historical eruptions in the 19th century originated
from the Goat Rocks area on the N flank, and were witnessed by early settlers.
Information Contacts: Cascades Volcano Observatory (CVO), U.S. Geological
Survey, 1300 SE Cardinal Court, Building 10, Suite 100, Vancouver, WA
98683-9589, USA (URL: vulcan.wr.usgs.gov/; Email:
GS-CVO-WEB@usgs.gov); Pacific Northwest Seismograph Network (PNSN),
Seismology Lab, University of Washington, Department of Earth and Space
Sciences, Box 351310, Seattle, WA 98195-1310, USA (URL:
www.pnsn.org/; Email: seis_info@ess.washington.edu).
Kick 'em Jenny
Grenada, West Indies
12.30°N, 61.64°W; summit elev. -185 m
The University of West Indies Seismic Research Unit (SRU) has augmented
their instrumental monitoring network and warning system at Kick 'em Jenny
submarine volcano. In addition to long-period and broadband seismometers to
sense earthquakes, they have also employed tide gauges to measure seawater
disturbances, hydrophones to discern submarine explosions, and tilt meters
and global positioning system (GPS) stations to detect long-term ground
deformation. The instruments may disclose anomalies and critical symptoms
before an eruption begins. Various combinations of these instruments were
installed at Mt. St. Catherine, Sauteurs, The Sisters Rocks, Isle de Ronde,
Isle de Caille, and Carriacou (figure 13).
Figure 13. A map indicating positions of monitoring instruments for the
current network at Kick 'em Jenny. Tilt meters and tide gauges were not
functioning at the time of this writing (early 2005). (Inset) Grenada and
Carriacou islands lie at the S end of the West Indies. Courtesy of SRU.
The NSF Caribbean Tsunami Workshop was held in March 2004 (Mercado-Irizarry
and Liu, 2004). The Workshop's program ended its Introduction section with
this statement: " . . . Kick 'em Jenny, close to the islands of the
southeastern Caribbean (just 10 km N of Grenada), is of much concern to the
local governments. Past eruptions during the last century (1939, 1965)
resulted in observed deep water tsunamis, with the one in 1939 being
measured as 1 m high [Shepherd, 2001]. The concern is such that, for the
first time (at least in the region), a banking institution (the Caribbean
Development Bank) is funding a monitoring program [at] the volcano."
A 29 December 2004 article entitled "Tsunami warning system for the
Caribbean," posted on the SRU website, also addressed the issue. It noted
that, "The devastation caused by the tsunami which ravaged several Asian
countries on 26th December 2004 has sparked discussion on the importance of
a tsunami early warning system in the Caribbean. While in theory such a
system may seem invaluable in light of the Asian disaster, scientists at
the Seismic Research Unit currently believe that several factors should be
seriously considered before assuming that a tsunami early warning system
would be beneficial to the region. Head of the Seismic Research Unit, Dr.
Richard Robertson, says that 'Before the region spends valuable resources
on setting up new instruments for a tsunami early warning system, we need
to strengthen our existing networks and focus on improving public education
and communication activities with regard to geologic hazards in the region.'"
Gas release, T-phase seismicity, and minor eruption clouds. The question of
whether or not there is strong fumarolic activity in the crater has been a
source of speculation for a number of years. It has been suggested that
warmed water rising in convection currents contributed to the reputation of
the Kick 'em Jenny region for rough water. The emission of large quantities
of bubbles was observed in 1989 when the submersible Johnson Sealink
entered the crater a few months after the 1988 eruption (Bulletin v. 14,
no. 5).
A water column containing a significant proportion of rising gas bubbles
results in a local lowering of the seawater's density. (The rising bubbles
displace some of the sea water, and at or near the sea surface they provide
negligible support to the ship, thus resulting in a loss of buoyancy for
ships passing over the volcano.) To account for this hazard, and the risk
posed by ejecta, an exclusion zone 1.5 km in radius was created over the
volcano (Shepherd, 2004).
At least 11 historical episodes of hydro-acoustic (T phase) signals have
been detected since 1939 when an eruption cloud rose 275 m above the sea
surface (Shepherd and Robson, 1967, Smith and Shepherd, 1995, Lindsay et
al., 2005). Material was also ejected during the 1974 eruption, and the
1988 eruption was associated with turbulent discolored water (Lindsay and
others, 2005). Some of these were described in Smithsonian reports dating
back to 1977.
Regarding T-Phase waves. A short-period wave group from a seismic source
that has propagated in part through the ocean is called T-phase or
T(ertiary)-wave (Linehan, 1940; Tolstoy and Ewing, 1950; Walker and
Hammond, 1998). The wave group propagates with low attenuation as
hydro-acoustic (compressional) waves in the ocean, constrained within a low
sound-speed wave guide (the sound fixing and ranging-SOFAR-channel) formed
by the sound-speed structure in the ocean. The T-phase signal may be picked
up by hydrophones in the ocean or by land seismometers. Upon incidence with
the continental shelf/slope, the wave group is transformed into ordinary
seismic waves that arrive considerably later than seismic wave groups from
the same source that propagated entirely through the solid Earth.
2002 and 2003 Surveys. A 2003 oceanographic survey of Kick 'em Jenny was
conducted jointly by the National Oceanic and Atmospheric Agency (NOAA),
SRU, and the University of Rhode Island (URI) using the NOAA Research
Vessel Ronald H. Brown. This survey supplemented data obtained previously
from a cruise passing the volcano on 12 March 2002 (Bulletin v. 27, no. 6).
That effort produced the bathymetric image shown in Bulletin v. 27 no. 6
and reproduced here as figure 14. The arcuate scarp on the image suggested
that the volcano was once the scene of sector collapse. The inferred
submarine debris avalanche has an estimated total volume of ~10 km^3, and a
maximum runout distance of at least 15 km (Sigurdsson and others, 2004;
Shepherd 2004). The collapse clearly occurred prior to the growth of the
small central edifice at Kick 'em Jenny. The ages of these various features
remain unknown.
Figure 14. Morphology of Kick 'em Jenny, as revealed by a multi-beam survey
by the NOAA Research Vessel Ronald H. Brown in March 2002 (N is toward the
top; for approximate scale, the sub-circular summit crater is about ~ 300 m
in diameter). The survey showed that the volcano's smaller, modern, active
cone sits nested within a larger U-shaped depression that wraps completely
around the cone's E side and opens toward the W. This larger depression
presumably formed by slope failure and generated a W-directed debris
avalanche that appears to lie within a marginal, confining levee. Courtesy
of NOAA.
Figures 15 and 16 highlight the discovery of other volcanic features on the
sea floor just E of Kick 'em Jenny. Little is known about them aside from
their basic morphology illuminated by the 2003 survey. Discoveries near
Kick 'em Jenny included three craters (C1, C2, and the largest, Kick 'em
Jack) and two domes (D1 and D2). The mutual relations and ages of these
newly recognized features remain uncertain.
Figure 15. Vertically exaggerated SeaBeam image of Kick 'em Jenny and newly
identified craters and domes discovered in March 2003. Kick 'em Jenny's
summit occurs adjacent to the crater rim at a depth of ~ 185 m. The deepest
point on Kick 'em Jenny's crater floor lies at ~ 264 m depth. The summit
sits at 12º18.024' N, 61º38.388' W (12.3004º N, 61.6398º W). The image's
left side is drawn N-S (i.e. N towards the upper left). Tick marks along
the margins are at 0.01 degree intervals, a spacing equivalent to 1.8-1.9
km. The distance between Kick 'em Jenny and Kick 'em Jack is about 4 km. A
vertical scale at the left indicates water depth: 0, -250, -500, and -750
m. Courtesy of NOAA and SRU.
Figure 16. Broad-scale SeaBeam image of Kick 'em Jenny and adjacent
features compiled from Ronald H. Brown cruise observations, March 2003.
North is up. The crater rim of Kick 'em Jenny ("rim"), as well as the rest
of the body of that dome, lie within a larger arcuate scarp that wraps
around the dome's E side. On the dome's W side the scarp extends outward,
crossing a swath of sea floor as two sub-parallel arms (indicated by the
arrows). Kick 'em Jack lies well outside this scarp, ~ 4 km SE of Kick 'em
Jenny. Courtesy of NOAA and SRU.
Background. Kick 'em Jenny, a historically active submarine volcano 8 km
off the N shore of Grenada, rises 1,300 m from the sea floor. The volcano
is located on the steep inner western slope of the Lesser Antilles
submarine ridge facing the Grenada Basin. Recent bathymetric surveys have
shown evidence for a major arcuate collapse structure that was the source
of a submarine debris avalanche that traveled more than 15 km to the W.
Numerous historical eruptions, mostly documented by acoustic signals, have
occurred since 1939, when an eruption cloud rose 275 m above the sea
surface. Prior to the 1939 eruption, which was witnessed by a large number
of people in northern Grenada, there had been no written mention of Kick
'em Jenny. Eruptions have involved both explosive activity and the quiet
extrusion of lava flows and lava domes in the summit crater; deep rumbling
noises have sometimes been heard onshore. Historical eruptions have
modified the morphology of the summit crater.
References: Linehan, D., 1940, Earthquakes in the West Indian region:
Transactions, American Geophysical Union, Pt. II, p. 229-232.
Mercado-Irizarry, A., and Liu, P. L.-F., 2004, NSF Caribbean Tsunami
Workshop, 30-31 March 2004: San Juan Beach Hotel, San Juan, P.R.,
sponsored by the U. S. National Science Foundation, Puerto Rico State
Emergency Management Agency, Department of Marine Sciences at the
University of Puerto Rico at Mayaguez, and the Sea Grant Program at the
University of Puerto Rico.
Lindsay, J. M., Shepherd, J.B., and Wilson D., 2005, Volcanic and
scientific activity at Kick 'em Jenny submarine volcano 2001-2002:
Implications for volcanic hazard in the Southern Grenadines, Lesser
Antilles: Natural Hazards, v. 31, p. 1-24.
Shepherd, J.B., and Robson, G.R., 1967, The source of the T-phase recorded
in the Eastern Caribbean on October 24, 1965: Bull. Seismol. Soc. Amer.,
v. 57, p. 227-234.
Shepherd, J.B., 2001, Marine and coastal hazards from Kick 'em Jenny
submarine volcano, southern Grenadine Islands (copyrighted slide-show
presentation): URL:
www.uwichill.edu.bb/bnccde/g...nny.html.
Shepherd, J.B., 2004, Report on studies of Kick 'em Jenny submarine volcano
March 2002 and March 2003 with updated estimates of marine and coastal
hazards: The University of the West Indies Seismic Research Unit, KEJ
Report Feb 2004, St. Augustine, Trinidad and Tobago, West Indies, 44 p.
Sigurdsson, H., Carey, S., and Wilson, D., 2004, Debris avalanche formation
at Kick 'em Jenny submarine volcano, in NSF Caribbean Tsunami Workshop,
30-31 March 2004, San Juan Beach Hotel, San Juan, P.R. (URL:
nsfctw.uprm.edu/agenda.html).
Smith, M., and Shepherd, J., 1995, Potential Cauchy-Poisson waves generated
by submarine eruptions of Kick 'em Jenny volcano: Natural Hazards, v. 11,
p. 75-94.
Tolstoy, I., and Ewing, M., 1950, The T phase of shallow-focus earthquakes:
Bulletin of the Seismological Society of America, v. 40, p. 25-51.
Walker, D.A., and Hammond, S.R., 1998, Historical Gorda Ridge T-phase
swarms; relationships to ridge structure and the tectonic and volcanic
state of the ridge during 1964-1966: Deep-Sea Research Part II, v. 45, n.
12, p. 2531-2545.
Information Contacts: Seismic Research Unit (SRU), The University of the
West Indies, St. Augustine, Trinidad & Tobago, West Indies (URL:
www.uwiseismic.com); Research Vessel Ronald H. Brown, National
Oceanic and Atmospheric Agency (NOAA), Marine Operations Center, Atlantic,
439 West York Street, Norfolk, VA 23510-1145, USA (URL:
oceanexplorer.noaa.gov/explorations/).
Marion Island
Southern Indian Ocean, South Africa
46.90°S, 37.75 E; summit. elev 1,230 m
A small volcanic eruption was observed on 24 June 2004 by a member of the
South African National Antarctic Programme's (SANAP) over-wintering team on
Marion Island (figure 17). While conducting fieldwork in a mountainous area
on the S part of the island, David Heddings was able to video an eruption
that comprised gas and small pieces of scoria (a few centimeters in diameter).
Figure 17. The SANAP base station, located on the E side of Marion Island.
Courtesy of Ian Meiklejohn.
While it has been assumed that small volcanic eruptions often take place on
Marion Island, the remoteness and hilly terrain over much of the island has
meant that such events have not been witnessed. The last confirmed eruption
on Marion took place in 1980 when ornithologists found a fresh basaltic
lava flow on the W side of the Island.
Background. Marion Island, South Africa's only historically active volcano,
lies at the SW end of a submarine plateau immediately south of the SW
Indian Ocean Ridge, opposite Prince Edward Island. The low profile of
24-km-wide dominantly basaltic and trachybasaltic Marion Island is formed
by two young shield volcanoes that rise above a flat-topped submarine
platform. The 1,230-m-high island is dotted by about 150 cinder cones,
smaller scoria cones, and coastal tuff cones. More than 130 scoria cones
and many lava flows formed during the Holocene. Many of these appear
younger than the 4,020 BP peat overlying one of the flows (Verwoerd, 1981).
Young unvegetated lava flows appear to be only a few hundred years old
(Verwoerd, 1967). The first historical eruption, during 1980, produced
explosive activity and lava flows from a 5-km-long fissure that extended
from the summit to the W coast.
Information Contacts: Ian Meiklejohn and David Hedding, University of
Pretoria, 0002, Pretoria, South Africa, 012-420 4049;(Email:
ian.meiklejohn@up.ac.za, URL: www.up.ac.za/).
__________________________________________________________
Global Volcanism Program, NHB E-421 Tel: (202) 633-1800
Smithsonian Institution Fax: (202) 357-2476
Washington, DC 20560-0119 Email: gvp@si.edu
Internet: www.volcano.si.edu/
-
Re: GVN Bulletin
Sun, May 15, 2005 - 11:45 PM*****************************************************
Bulletin of the Global Volcanism Network, March 2005
*****************************************************
From: Ed Venzke <venzke@volcano.si.edu>
Bulletin of the Global Volcanism Network
Volume 30, Number 3, March 2005
Jun Jaegyu (Antarctica) Newly described submarine volcano near the tip of
the Antarctic Peninsula
Colima (Mexico) Lava flows up to 2.4 km long; March 2005 explosions;
collapse on summit
Soufriere St. Vincent (St. Vincent) Anomalous winds spread sulfurous odors,
causing unwarranted fears
Soufriere Hills (Montserrat) Comparative quiet during 26 November 2004 to 4
March 2005
Kliuchevskoi (Kamchatka Peninsula) Strombolian eruptions and lava flows
during January-March 2005
Bezymianny (Kamchatka Peninsula) Explosive eruption on 11 January 2005
inferred from seismic data
Canlaon (Philippines) Frequent ash emissions in March and April 2005;
access remains restricted
Ibu (Indonesia) Periodic ash emissions during June-August 2004 and inferred
dome growth
Kavachi (Solomon Islands) Eruption on 15 March 2004 breaks the water surface
Lopevi (Vanuatu) Several lines of data confirm ongoing eruptions at this
frequently erupting volcano
OBITUARY Helicopter crash in the Philippines kills four PHIVOLCS staff and
former director
Editors: Rick Wunderman, Edward Venzke, and Gari Mayberry
Volunteer Staff: Catherine Galley, Robert Andrews, Susan Nasr, William
Henoch, Clement Prior, and Jacquelyn Gluck
Jun Jaegyu
Antarctic Sound, Antarctica
63.48°S, 56.43°W; summit elev. -275 m (submarine)
Jun Jaegyu is a young volcano near the Antarctic Peninsula visited in May
2004 by researchers from a group of United States and Canadian universities
aboard the U.S. National Science Foundation research vessel Laurence M.
Gould (Cruise LMG04-04). The expedition's chief scientist was Eugene Domack
of Hamilton College.
Prior to this cruise, bathymetric swath maps from 2002 revealed a
symmetrical volcano that had not been scoured by the advance and retreat of
glaciers. The 2004 cruise dredged the volcano and found material that
included fresh basalt in a flank area devoid of colonizing bottom-dwelling
organisms. In contrast, observations suggested that other portions of the
volcano were heavily colonized by bottom-dwelling organisms. The discovery
of the volcano corroborated mariners' reports of discolored water in the
area. These observations, and a thermal anomaly, were all consistent with
comparatively recent volcanic activity.
The volcano is located on the Antarctic continental shelf in the southern
Antarctic Sound, ~9 km N of the easternmost point of Andersson Island and
NW of Rosamel Island (figure 1), N of the mapped boundary of Late Cenozoic
volcanic rocks. Swath bathymetric mapping indicated that the volcano stands
~700 m above the seafloor (at a depth of ~1,000 m) and thus extends to
within ~275 m of the ocean surface. The seamount has an elongate,
symmetrical shape and contains ~1.5 km^3 of volcanic rock.
Figure 1. Jun Jaegyu submarine volcano (J) lies E of the extreme tip of the
Antarctic Peninsula (see inset map) in the Antarctic sound, an area
sheltered by several islands. Paulet Island, another volcano of probable
Holocene age, lies just outside the Antarctic Sound on the SE side of
Dundee Island. A better known Holocene volcano, Deception Island, lies to
the NW (adjacent to the South Shetland Islands) as indicated by the arrow.
Base map copied from Northern Graham Land and South Shetland Island,
British Antarctic Territory Geologic Map (1:500,000) from BAS 500 G, sheet
2, edition 1, 1978. Note that map coordinates shown are in degrees and
minutes (eg. 57 00', 57 degrees and 0 minutes).
Two observed positive thermal anomalies (up to 0.052ºC), recorded by
temperature probes towed over the volcano from S to N, may be associated
with two active volcanic centers. The more complex N temperature anomaly
may also be associated with what appeared to be fresher lava flows.
The volcano lies along a NW-SE oriented fault scarp. Material dredged from
the volcano have not been dated because accurately dating vesicular,
partially altered, young submarine basalts is problematic at best. No gas
samples were collected during this cruise.
Ashley Hatfield, a participant in the cruise and an undergraduate geology
student at Hamilton College, advised by David Bailey and Eugene Domack,
analyzed representative samples for whole-rock major and trace elements
using XRF (X-ray fluorescence spectroscopy) and ICP-MS (inductively coupled
plasma mass spectrometry). The samples are generally angular, glassy, and
vesicular, having plagioclase, olivine, and clinopyroxene present as
phenocryst phases, and with small rounded xenoliths being common (Hatfield
and others, 2004). The samples were classified as alkali basalts and
trachybasalts, and their chemical signatures were consistent with other
known volcanoes throughout the northern Antarctic Peninsula.
Hatfield noted that the volcano is named in honor of Jun Jaegyu, a young
Korean scientist who lost his life during the 2003 field season in the
South Shetland islands. He was participating in the Korean Antarctic
Program through their geophysical observatory based in the South Shetland
Islands (King Sejong Station, established in 1988 on the Barton Peninsula,
King George Island at 62°13.4818' S, 58°47.4744' W).
The scientific crew for this cruise included Hatfield, Bailey, and Domack,
(Department of Geology, Hamilton College, Clinton, New York); Stefanie
Brachfield, (Department of Earth and Environmental Sciences, Montclair
State University, Upper Montclair, New Jersey); Robert Gilbert (Department
of Geological Sciences, Queen's University, Kingston, Ontario); Scott
Ishman (Department of Geology, Southern Illinois University, Carbondale,
Illinois); Gerd Krahmann (Lamont-Doherty Earth Observatory of Columbia
University, Palisades, New York); and Amy Leventer (Department of Geology,
Colgate University, Hamilton, New York).
Background. A morphologically youthful submarine volcanic center was
discovered in the Antarctic Sound off the tip of the Antarctic Peninsula
during oceanographic cruises in 2002 and 2004. Jun Jaegyu volcano rises to
within 275 m of sea surface. It is the northernmost volcanic feature of the
James Ross Island volcanic group, and lies ~32 km WNW of Paulet Island, a
small volcano of probable Holocene age. The flanks of the newly documented
volcano display fresh volcanic rocks devoid of marine organisms that
blanket most of the edifice. Dredged samples included alkali basalts and
trachybasaltic rocks. Mild positive thermal anomalies were detected over
two possible submarine centers, and mariners' reports had noted discolored
water in this area.
Reference: Hatfield, A., Bailey, D., Domack, E., Brachfeld, S., Gilbert,
R., Ishman, S., Krahmann, G., and Leventer, A., 2004, Jun Jaegyu volcano; A
recently discovered alkali basalt volcano in Antarctic Sound, Antarctica:
Eos, Transactions, American Geophysical Union, 85(47), Fall Meeting
Supplement, Abstract T11A-1248.
Information Contacts: David G. Bailey, Eugene Domack, and Ashley K.
Hatfield, Department of Geosciences, Hamilton College, 198 College Hill
Rd., Clinton, NY 13323, USA (Email: dbailey@hamilton.edu,
edomack@hamilton.edu, and ahatfield@hamilton.edu).
Colima
Mexico
19.514°N, 103.62°W; summit elev. 3,850 m
All times are local (= UTC + 6 hours)
The recent extrusion of block-lava that began on 30 September 2004
continued through November 2004. Lava flows formed on the N and WNW flanks,
with the respective dimensions ~2,400 m long by ~300 m wide, and ~600 m
long by ~200 m wide. The total volume of erupted material, including lava
and pyroclastic flows, was about 8.3 x 10^6 m^3 (Bulletin v. 30, no. 1).
The termination of lava effusion was followed by intermittent explosive
activity represented mainly by small gas-and-ash Vulcanian explosions.
Their number gradually decreased during December 2004-March 2005 (figure 2).
Figure 2. Eruptive activity of at Colima during September 2004-March 2005.
The variations in the number of earthquakes produced by rockfalls and
pyroclastic flows (heavy line) and by explosions and exhalations (dashed
line) are shown. Double arrows show the beginning (B) and the end (E) of
lava extrusion; three single arrows indicate the explosions of 10, 13, and
26 March. Courtesy of Colima Volcano Observatory.
Three relatively large explosions occurred in March (on the 10th, the 13th,
and the 26th). Those of 10 and 13 March formed eruptive columns with
heights of ~5 km above the crater and were accompanied by pyroclastic flows
down the S flank. The lengths of associated pyroclastic flows did not
exceed 2.8 km. The largest explosion to take place on 13 March generated
fallout that included lapilli with a diameter of up to 2 cm. Ash fell at a
distance of 12.5 km to the NE of the volcano (in the village of Los Mazos,
Jalisco).
Scientists made E-W topographic profiles on 12 October 2004 and 18 March
2005 (figure 3). The profiles crossed an area on the summit's S flank. They
disclosed that during this intervening interval there had been a collapse
over an area of ~2,500 m^2.
Figure 3. Two topographic profiles across the summit of Colima from the S
flank made on 12 October 2004 and 18 March 2005. Courtesy of Colima Volcano
Observatory.
Background. The Colima volcanic complex is the most prominent volcanic
center of the western Mexican Volcanic Belt. It consists of two
southward-younging volcanoes, Nevado de Colima (the 4,320 m high point of
the complex) to the N and the 3,850-m-high historically active Volcan de
Colima to the S. A group of cinder cones of probable late-Pleistocene age
is located on the floor of the Colima graben W and E of the Colima complex.
Volcan de Colima (also known as Volcan Fuego) is a youthful stratovolcano
constructed within a 5-km-wide caldera, breached to the S, that has been
the source of large debris avalanches. Major slope failures have occurred
repeatedly from both the Nevado and Colima cones, and have produced a thick
apron of debris-avalanche deposits on three sides of the complex. Frequent
historical eruptions date back to the 16th century. Occasional major
explosive eruptions (most recently in 1913) have destroyed the summit and
left a deep, steep-sided crater that was slowly refilled and then
overtopped by lava dome growth.
Information Contacts: Observatorio Vulcanologico de la Universidad de
Colima, Colima, Col., 28045, Mexico (Email: ovc@cgic.ucol.mx; URL:
www.ucol.mx/volcan/).
Soufriere St. Vincent
St. Vincent, West Indies
13.33°N, 61.18°W; summit elev. 1,220 m
All times are local (= UTC - 4 hours)
Widespread sulfurous odors and haze during mid-February 2005 on the island
of St. Vincent and as far as the Grenadines (50-75 km S) led some people to
conclude that the smells reflected increased output of volcanic gases from
the Soufriere volcano, St. Vincent, a possible harbinger of an eruption.
Sulfurous odors are common on the volcano's W flank, but less frequent on
other parts of the island.
Scientists determined that typical winds diminish the sulfurous odors over
much of the island, and the onset of the odors resulted from changes in
wind patterns rather than increased gas output or other demonstrable changes.
The Seismic Research Unit (SRU) collaborates with a small local unit called
the Soufriere Monitoring Unit (which operates from the Ministry of
Agriculture in Kingstown). The following report on the subject comes from
SRU's Richard Robertson.
"During the night of 16 February and most of the day of 17 February there
were widespread reports of sulfurous smells throughout southern St. Vincent
and as far as the Grenadines. The day of the 17th was hazy; people put
these two things together and came up with the conclusion that the volcano
was acting up. The sulfur smell is unusual since the wind direction is such
that most of the smell from the fumaroles at the summit of the volcano gets
blown out to sea and is usually only smelt by a few residents on the
eastern flank of the volcano.
"[SRU] . . . worked with Ms. Aisha Samuels, the head of the local volcano
monitoring unit, to first investigate the report and later to quell fears
that the volcano was doing anything unusual. We determined very early on
that nothing serious was happening, since we have seismic stations both on
the volcano and throughout the island [figure 4], none of which had
recorded any increased seismicity. Further, we had just completed a GPS
campaign on the island during January 2005, which revealed nothing unusual.
It also involved two days of measurements on the summit of the volcano
during which scientists were in very close proximity to the vent from which
future eruptions will [likely] originate.
Figure 4. A sketch map showing the island of St. Vincent, including
Soufriere volcano, other volcanic centers, geographic features, and Seismic
Research Unit monitoring instrumentation (as of February 2004). January
2005 discussion of the instrumentation noted that it then included five
seismic stations, eight GPS stations, and several dry-tilt sites. Courtesy
of SRU.
"We quickly determined that the reported 'activity' was due to an unusual
southerly wind combined with the phenomena of Sahara dust which is common
around this time of the year in St. Vincent and which results in very hazy
conditions. However, to completely rule out the possibility of anything
unusual happening in the crater that may not have been possibly detected by
our various measurements, we advised the local Unit that they should visit
the crater summit the next day (18 February)."
That visit found nothing out of the ordinary. Accordingly, SRU did not
think it necessary to update their website since it was so
insignificant-"'a 10 day wonder' as they say in the West Indies, or a
'pseudo-crisis.'" Such reports are common for St. Vincent and the entire
region.
Background. Soufriere St. Vincent is the northernmost and youngest volcano
on St. Vincent island. The 1.6-km wide summit crater, whose NE rim is cut
by a crater formed in 1812, lies on the SW margin of the 2.2-km-wide Somma
crater, which is breached widely to the SW as a result of slope failure.
The first historical eruption of the volcano took place during 1718; it and
the 1812 eruption produced major explosions. Much of the N end of the
island was devastated by a major eruption in 1902 that coincided with the
catastrophic Mont Pelee eruption on Martinique. A lava dome was emplaced in
the summit crater in 1971 during a strictly effusive eruption, forming an
island in a lake that filled the crater prior to an eruption in 1979. The
lake was then largely ejected during a series of explosive eruptions, and
the dome was replaced with another.
Information Contacts: Richard Robertson, Seismic Research Unit, The
University of the West Indies, St. Augustine, Trinidad (URL:
www.uwiseismic.com/); Aisha Samuel, Soufriere Monitoring Unit,
Ministry of Agriculture, St. Vincent.
Soufriere Hills
Montserrat, West Indies
16.72°N, 62.18°W; summit elev. 915 m
All times are local (= UTC - 4 hours)
This report covers the period 26 November 2004 to 4 March 2005. Soufriere
Hills volcano remained quiet after late November, with seismic signals, gas
emissions, and rockfalls all decreasing (table 1 and Bulletin v. 29 no. 10).
Table 1. Geophysical and geochemical data recorded at Soufriere Hills, 26
November 2004 to 4 March 2005. Wind directions or trouble with
gas-monitoring equipment prevented measurement of SO2 fluxes on some days.
Courtesy of MVO.
Date Seismicity Hybrid Mixed VT LP SO2
flux Rockfalls
(2004-2005) level EQ's EQ's EQ's EQ's (metric
tons/day)
26 Nov-03
Dec -- 9 -- 7 -- 130-590 4
03 Dec-10
Dec -- 7 -- -- -- 250-370 1
10 Dec-17
Dec -- 6 -- 7 -- 290-450 --
17 Dec-24
Dec -- 6 -- 1 -- 200-500 --
24 Dec-31
Dec -- 6 -- 2 1 300-550 --
31 Dec-07
Jan -- 4 -- -- -- 310-400 --
07 Jan-14
Jan -- 5 -- 5 -- 180-511 --
14 Jan-21
Jan -- 2 -- -- -- 300-3801 2
21 Jan-28
Jan -- 5 -- -- 1 350-6701 --
28 Jan-04
Feb -- 2 -- 1 7 4101 --
04 Feb-11
Feb low -- -- -- -- -- --
11 Feb-18
Feb low -- -- -- -- -- --
18 Feb-25
Feb low -- -- -- -- 280-9801 --
25 Feb-04
Mar low 6 -- 3 -- 6721 2
While volcanic-tectonic and hybrid earthquakes (as many as 40/week) shook
SHV from mid-October to late November, few were recorded between late
November and early March (table 1). During the week of 25 February, winds
shifted and carried the smell of sulfur to northern parts of the island.
However, SO2 emissions remained low and stable throughout December,
January, and February. The average for this reporting period was ~400
tons/day, which is below the long-term average of 500 tons/day.
Rain and mudflows have also subsided. A mudflow in the Belham Valley on 15
December was the only event recorded for this reporting period.
An exceptionally clear day enabled scientists to obtain unusually clear
photos on 1 February 2005 (figures 5, 6, and 7). Flights were made during
November, December, and January as well. During the November-February
interval, scientists saw relatively few changes in the surface morphology.
Chances Pond, the pool of brownish water sitting in the explosion pit
formed on 3 March 2004, still remained. MVO scientists noted around 26
November 2004 that the pond had changed from brownish to milky.
Figure 5. Montserrat from the NNE at an altitude of ~ 1,500 m, clearly
showing the island's three main volcanic centers: the oldest and extinct
Silver Hills (more than a million years old) in the foreground; the
highest, densely foliated Centre Hills (also extinct, 0.5-1 million years
old), and the steaming Soufriere Hills (220,000 years old), furthest away.
Courtesy of MVO.
Figure 6. A photo of Soufriere Hills volcano taken from the NE showing the
dome within the breached summit crater, and the SW-flank morphology. Much
of the steam discharging was attributed to fumaroles. Photographed on 1
February 2005. Courtesy of MVO.
Figure 7. Recent deposits on the SW flank of Soufriere Hills as viewed from
the NE on 1 February 2005. Prominent deltas appear at the mouths of the
drainages shown, particularly at the mouth of the Tar River Valley.
Courtesy of MVO.
On 3 March 2005, scientists took a Fourier Transform Infrared spectrometer
(FTIR) reading of the gas escaping from the crater vent at the summit
(figure 6). The gas plume contained a ratio of hydrogen chloride to sulfur
dioxide by mass of 0.35. This ratio showed no change since February.
In September 2004, the Scientific Advisory Committee on Montserrat Volcanic
Activity (SAC) joined MVO staff at the Montserrat Volcano Observatory to
discuss recent activity (SAC, 2004). "Few signs of surface activity" was
their appraisal of the period since March 2004. There had been little gas
venting, ash venting, or tremor in six months, and no lava extrusion in 15
months. This pause in activity, the SAC predicted, will last ~26 months,
but could last as long as 170 months. SAC estimated risks for a variety of
circumstances.
Readers can access full reports issued by the SAC at the MVO website. The
main report summarizes conclusions drawn from the meeting, while the
technical report includes long-term monitoring data and risk assessments.
Background. The complex andesitic Soufriere Hills volcano occupies the
southern half of the island of Montserrat. The summit area consists
primarily of a series of lava domes emplaced along an ESE-trending zone.
Prior to 1995, the youngest dome was Castle Peak, which was located in
English's Crater, a 1-km-wide crater breached widely to the E.
Block-and-ash flow and surge deposits associated with dome growth
predominate in flank deposits. Non-eruptive seismic swarms occurred at
30-year intervals in the 20th century, but with the exception of a
17th-century eruption, no historical eruptions were recorded on Montserrat
until 1995. Long-term small-to-moderate ash eruptions beginning in that
year were later accompanied by lava dome growth and pyroclastic flows that
forced evacuation of the southern half of the island and ultimately
destroyed the capital city of Plymouth, causing major social and economic
disruption to the island.
Reference: Scientific Advisory Committee on Montserrat Volcanic Activity
(SAC), 2004, Assessment of the hazards and risks associted with the
Soufriere Hills volcano, Montserrat: Second Report of the Scientific
Advisory Committee on Montserrat Volcanic Activity, parts I (Main Report,
24 p.) and II (Technical Report, 26 p.).
Information Contacts: Montserrat Volcano Observatory (MVO), Fleming,
Montserrat, West Indies (URL: www.mvo.ms/).
Kliuchevskoi
Kamchatka Peninsula
56.057°N, 160.638°E; summit elev. 4,835 m
All times are local (= UTC + 12 hours)
From April to November 2004, the hazard status (Concern Color Code)
remained at Yellow, with seismicity at background levels throughout this
time, and occasional fumarole activity. Around 26 November 2004, the status
was reduced from Yellow to Green, the lowest level. During November 2004,
seismicity remained at background levels. Gas-and-steam plumes were seen up
to 5 km altitude on 24 November 2004 and weak fumarolic activity was
observed on several days. Kliuchevskoi was last reported on in April 2004
(Bulletin v. 29, no. 4) and this report covers the interval through 31
March 2005.
On 14 January 2005 the Kamchatkan Volcanic Eruption Response Team (KVERT)
raised the status at Kliuchevskoi from Green to Yellow as seismic activity
at the volcano increased. On 12 January, around 21 shallow earthquakes of M
1.0-1.7 and weak volcanic tremor were recorded. According to visual
observations, weak gas-and-steam plumes were noted during 6-8 and 12
January. The plumes extended E from the volcano on 7 January and SW for 5
km on 12 January.
On 16 January 2005 KVERT raised the status again, from Yellow to Orange, as
seismic activity increased significantly. During 13-14 January, 15 shallow
earthquakes of over M 1.25 were recorded, along with an increase in the
amplitude of volcanic tremor. Visual observations on 14 January noted a
weak gas-and-steam plume that extended N from the volcano. Satellite data
showed a bright thermal anomaly over the summit on 15 January.
During the third week of January, the total number of shallow earthquakes
continued to increase. Gas-and-steam plumes rose to ~800 m above the lava
dome. Incandescence was visible in the volcano's crater on several nights.
Strombolian eruptions occurred during 20-23 and 27 January. Explosions sent
volcanic bombs 50-300 m above the crater on several nights. Gas-and-steam
plumes rose to a maximum height of 1.5 km above the crater. On 21 January a
gas-and-steam plume with small amounts of ash extended as far as 23 km NE
of the volcano. Throughout January seismicity was above background, with a
large number of shallow earthquakes recorded daily. Gas-and-steam plumes
that rose to ~1 km above the volcano's crater drifted SW on 29 January and
NW on 31 January. A small amount of ash fell in the town of Klyuchi, about
25 km to the NE, on 31 January.
On 1 February around 1000, a mudflow carrying large blocks and trees
traveled ~6 km down Kliuchevskoi's NW flank into the Kruten'kaya River. The
mudflow reached a height of a few meters and trees were covered with mud to
~1.5 m. On 6, 8, and 9 February, ash plumes rose ~2.5 km above the
volcano's crater. Gas-and-steam plumes rose to ~3 km during 6-9 February. A
cinder cone was noted in the volcano's crater on 6 February. Fresh ash
deposits were seen on the SW flank of Ushkovsky volcano (NW of
Kliuchevskoi) on 7 February, and in Klyuchi on 9 February.
Throughout the first week of February there were Strombolian eruptions in
the terminal crater of Kliuchevskoi, and a lava flow traveled into
Krestovsky channel on the volcano's NW flank. Phreatic bursts occurred in
this channel when the lava contacted glaciers during 6-9 February and 12-13
February. Ash plumes rose ~3 km above the volcano's crater during 12-14
February. During 12-16 February, volcanic bombs were hurled 300-500 m above
the crater, Strombolian eruptions occurred in the crater, and lava again
traveled into the Krestovsky channel. On 16 February, a mudflow extended 27
km. According to a news report, a lava flow from Kliuchevskoi melted a
large section of Ehrman glacier on 21 February 2005.
Moderate seismic and volcanic activity continued at Kliuchevskoi during 24
February to 4 March. On 24 February lava continued to travel down the
Krestovsky channel. Strombolian activity during this time sent plumes to ~1
km above the volcano. Ash fell in the village of Icha, about 275 km to the
SW on 26 February, and in Kozyrevsk, about 25 km to the W, on 1 March. Ash
plumes were visible on satellite imagery on several days. During the first
two weeks of March 2005, eruptions continued. Strombolian explosions
occurred intermittently from a cinder cone in the summit crater. Lava flows
extend from this cone down the NW flank. Occasional vigorous explosions
from the summit crater and along the path of the lava flow produced ash
plumes as high as 7-8 km and traveled many tens or hundreds of kilometers
downwind. Ash-and-gas plumes rose up to 3.2 km above the crater on 10-16
March and extended up to 150 km in various directions. Ash fell at
Kozyrevsk on 11 March. Strombolian bursts rose about 500-1,000 m above the
summit crater. Two lava flows were observed on the volcano's NW slope on 15
March. Clouds obscured the volcano at other times. According to satellite
data, a large thermal anomaly was registered at the volcano during the
second week of March.
During 11-18 March, Strombolian explosions occurred intermittently from a
cinder cone in the summit crater. Lava flows extended from this cinder cone
down the NW flank. Occasional vigorous explosions from the summit crater
and along the path of the lava flow produced ash plumes that reached as
high as 7-8 km altitude and drifted many tens or hundreds of kilometers
downwind. Seismicity was above background at this time. On 11-12 March
ash-and-gas plumes rose to 3.2 km above the crater. Ash fell in the town of
Kozyrevsk, 30 km to the W, on 11 March. Strombolian bursts rose 500-1,000 m
above the summit crater. On 15 March two lava flows were observed on the NW
slope. The amplitude of volcanic tremor was about 12-13 x 10^-6 m/s on
18-21 March and increased to about 46.0 x 10^-6 m/s on 22 March. From 1730
till 1900 on 23 March it was up to 62 x 10^-6 m/s.
On 24 March KVERT raised the hazard status to Red (the highest level) due
to increased seismic and volcanic activity. A gas-and-steam plume
containing ash rose to ~7.5 km altitude on 22 March and ~8.5 km altitude on
23 March, extending NW. Ash fell in the town of Klyuchi during 23-24 March.
According to data from AMC (Airport Meteorological Center) at Yelizovo, 340
km S, an ash plume that rose to ~7 km altitude and extended 70-80 km to the
NW was observed by pilots on 23 March. The amplitude of volcanic tremor
decreased from 62 x 10^-6 m/s on 23 March to 26-22 x 10^-6 m/s on 25-26
March. Satellite data indicated a 2- to 6-pixel (through the clouds)
thermal anomaly over the volcano throughout the last week of March.
Ash-and-gas plumes extended from the volcano 35 km N and 80 km W on 25
March. Seismometers detected a great number of shallow earthquakes and 27
earthquakes of Ml = 1.5-2.1.
During about 27-28 March seismic activity at Kliuchevskoi decreased,
leading KVERT to reduce the status to Orange. According to visual and video
data during 27-28 March, a gas-and-steam plume containing some ash rose
~200 m above the crater and extended W. Ash-and-gas plumes rose to
2,500-3,000 m above the crater and extended SE on 28 March, and NE on 29
March. Incandescence above the summit crater was observed on 28 March.
According to the data from the AMC at Yelizovo, an ash-and-gas plume rising
about 2,000 m above the crater at 1420 on 31 March was observed by pilots.
Ash-and-gas plumes extended 250 km SE on 28 March, 270 km NE on 29 March,
and 100 km NW on 31 March.
Background. Kliuchevskoi is Kamchatka's highest and most active volcano.
Since its origin about 6,000 years ago, the beautifully symmetrical,
4,835-m-high basaltic stratovolcano has produced frequent moderate-volume
explosive and effusive eruptions without major periods of inactivity.
Kliuchevskoi rises above a saddle NE of sharp-peaked Kamen volcano and lies
SE of the broad Ushkovsky massif. More than 100 flank eruptions have
occurred at Kliuchevskoi during the past roughly 3,000 years, with most
lateral craters and cones occurring along radial fissures between the
unconfined NE-to-SE flanks of the conical volcano between 500 m and 3,600 m
elevation. The morphology of its 700-m-wide summit crater has been
frequently modified by historical eruptions, which have been recorded since
the late-17th century. Historical eruptions have originated primarily from
the summit crater, but have also included numerous major explosive and
effusive eruptions from flank craters.
Information Contacts: Olga Girina, Kamchatka Volcanic Eruptions Response
Team (KVERT), a cooperative program of the Institute of Volcanic Geology
and Geochemistry, Far East Division, Russian Academy of Sciences, Piip Ave.
9, Petropavlovsk-Kamchatskii 683006, Russia (Email: girina@kcs.iks.ru), the
Kamchatka Experimental and Methodical Seismological Department (KEMSD), GS
RAS (Russia), and the Alaska Volcano Observatory (USA); Alaska Volcano
Observatory (AVO), cooperative program of the U.S. Geological Survey, 4200
University Drive, Anchorage, AK 99508-4667, USA (URL:
www.avo.alaska.edu/; Email: tlmurray@ usgs.gov), the Geophysical
Institute, University of Alaska, P.O. Box 757320, Fairbanks, AK 99775-7320,
USA (Email: eisch@dino.gi.alaska.edu), and the Alaska Division of
Geological and Geophysical Surveys, 794 University Ave., Suite 200,
Fairbanks, AK 99709, USA (Email: cnye@giseis.alaska.edu).
Bezymianny
Kamchatka Peninsula
55.978°N, 160.587°E; summit elev. 2,882 m
All times are local (= UTC + 12 hours)
Bezymianny was reported on in Bulletin v. 29, no. 5, covering the June 2004
eruption that was characterized by viscous lava flows and large ash plumes.
This report covers the interval from July 2004 through February 2005. From
July 2004 to December 2004, unrest and fumarolic activity were virtually
continuous. The Concern Code Color (hazard status) remained at Yellow
throughout much of this time, and seismicity was at or below background
levels. The lava dome of the volcano continued to grow, and satellite data
frequently indicated a thermal anomaly over the dome. Gas-steam plumes were
observed almost daily from Klyuchi about 50 km away, rising to 3-5 km
altitude, and extending in various directions for 10-15 km.
KVERT raised the hazard status from Yellow to Orange on 7 January as
seismicity increased. On 11 January, KVERT raised the status from Orange to
Red (the highest level). An explosive eruption, inferred from seismic data,
began at 2002 on 11 January 2005 and was believed to have produced an ash
column to 8-10 km altitude. No visual or satellite data were available as
dense clouds obscured the volcano. Seismic activity was above background
levels during the first week of January and increased continuously. About
60 earthquakes of magnitude 1.25-2.25, and numerous weaker, shallow events
registered during 7-11 January. Intermittent volcanic tremor was recorded
on 10 January.
The hazard status was lowered from Red to Orange on 12 January when seismic
activity returned to background levels following the eruption of 11
January. Seismicity remained at background levels so the status was lowered
from Orange to Yellow on 14 January.
During February 2005 gas-steam plumes were observed frequently, rising
50-1,000 m above the dome and drifting 10-15 km in various directions.
Satellite data frequently indicated a thermal anomaly over the dome. The
status remained at Yellow as of 29 April 2005.
Background. Prior to its noted 1955-56 eruption, Bezymianny volcano had
been considered extinct. The modern Bezymianny volcano, much smaller in
size than its massive neighbors Kamen and Kliuchevskoi, was formed about
4,700 years ago over a late-Pleistocene lava-dome complex and an ancestral
volcano that was built between about 11,000-7,000 years ago. Three periods
of intensified activity have occurred during the past 3,000 years. The
latest period, which was preceded by a 1,000-year quiescence, began with
the dramatic 1955-56 eruption. This eruption, similar to that of Mount St.
Helens in 1980, produced a large horseshoe-shaped crater that was formed by
collapse of the summit and an associated lateral blast. Subsequent episodic
but ongoing lava-dome growth, accompanied by intermittent explosive
activity and pyroclastic flows, has largely filled the 1956 crater.
Information Contacts: Olga Girina, Kamchatka Volcanic Eruptions Response
Team (KVERT), a cooperative program of the Institute of Volcanic Geology
and Geochemistry, Far East Division, Russian Academy of Sciences, Piip Ave.
9, Petropavlovsk-Kamchatskii 683006, Russia (Email: girina@kcs.iks.ru), the
Kamchatka Experimental and Methodical Seismological Department (KEMSD), GS
RAS (Russia), and the Alaska Volcano Observatory (USA); Alaska Volcano
Observatory (AVO), a cooperative program of the U.S. Geological Survey,
4200 University Drive, Anchorage, AK 99508-4667, USA (URL:
www.avo.alaska.edu/; Email: tlmurray@ usgs.gov), the Geophysical
Institute, University of Alaska, P.O. Box 757320, Fairbanks, AK 99775-7320,
USA (Email: eisch@dino.gi.alaska.edu), and the Alaska Division of
Geological and Geophysical Surveys, 794 University Ave., Suite 200,
Fairbanks, AK 99709, USA (Email: cnye@giseis.alaska.edu).
Canlaon
central Philippines
10.412°N, 123.132°E; summit elev. 2,435 m
All times are local (= UTC + 8 hours)
Ash emissions and sporadic seismicity at Canlaon between March 2003 and
March 2004 were reported in Bulletin v. 29, no.12. A brief ash emission
began at Canlaon around 0930 on 21 January 2005. The eruption cloud rose
~500 m above the active crater and drifted WNW and SW. No coincident
volcanic earthquakes were recorded. Fine ash was deposited in the city of
Cabagnaan, ~5.5 km SW of the crater. The Philippine Institute of
Volcanology and Seismology (PHIVOLCS) advised the public to avoid entering
the 4-km-radius Permanent Danger Zone around Canlaon.
Ash emissions began again on 20 March around 1300. Small amounts of ash
fell in the town of Guintubdan 5 km W of the volcano. During 24 March to 4
April, sporadic ash emissions rose to a maximum of 1 km above the volcano.
During this time ash fell in the towns of La Castellana (16 km SW of the
crater), Upper Sag-ang, Yubo (5-6 km SW), and Guintubdan (5-6 km WNW). Due
to this unrest, PHIVOLCS raised the Alert Level from 0 to 1 (on a scale of
0-5) on 30 March. According to a news article, pilots were advised to avoid
flying near Canlaon.
On March 22 the Provincial Disaster Management Team (PDMT) warned it would
apprehend trekkers and faith healers who ventured to Mount Canlaon during
Holy Week. Trekking to Mount Canlaon has become a practice by some faith
healers and mountaineers who believe that the volcano is a source of
supernatural powers.
On 31 March at 0601 and 1715, two mild ash ejections reached heights of
about 200-300 m above the summit before drifting NW and SW. Ash was
deposited at Guintubdan, Upper Sag-ang, and Upper Mansalanao. A low-energy
ash emission on 7 April at 1429 generated a cloud which rose to a height of
~100 m above the crater and drifted SW. According to PHIVOLCS, the seismic
monitoring network around the volcano did not record any earthquakes during
this event. During 13-14 April, mild ash emissions produced plumes to a
height of ~700 m above the crater. During 15-17 April, moderate-to-strong
emissions produced ash plumes to ~2 km above the crater and deposited ash
in villages as far as La Castellana. None of these ash emissions was
associated with seismicity, indicating that the activity is likely
hydrothermal in nature, and taking place at shallow levels in the crater.
Throughout this period Canlaon remained at Alert Level 1. As of the end of
April 2005, the 4-km-radius Permanent Danger Zone (PDZ) was restricted and
all treks to the summit remained suspended.
Background. Canlaon volcano (also spelled Kanlaon), the most active of the
central Philippines, forms the highest point on the island of Negros. The
massive 2,435-m-high stratovolcano is dotted with fissure-controlled
pyroclastic cones and craters, many of which are filled by lakes. The
summit of Canlaon contains a broad elongated northern caldera with a crater
lake and a smaller, but higher, historically active crater to the S. The
largest debris avalanche known in the Philippines traveled 33 km to the SW
from Canlaon. Historical eruptions, recorded since 1866, have typically
consisted of phreatic explosions of small-to-moderate size that produce
minor ashfalls near the volcano.
Information Contacts: Philippine Institute of Volcanology and Seismology
(PHIVOLCS), Department of Science and Technology, PHIVOLCS Building, C.P.
Garcia Avenue, Univ. of the Philippines Campus, Diliman, Quezon City,
Philippines (URL: www.phivolcs.dost.gov.ph/); Chris Newhall, USGS,
Box 351310, University of Washington, Seattle, WA 98195-1310, USA(Email:
cnewhall@ess.washington.edu); Philippine Star (URL: www.philstar.com/).
Ibu
Halmahera, Indonesia
1.48°N, 127.63°E; summit elev. 1,325 m
The Directorate of Volcanology and Geological Hazard Mitigation (DVGHM)
released ten nearly identical weekly reports on Ibu during 31 May-29 August
2004. They noted that Ibu emitted "white ash" (steam plumes) reaching
~50-150 m above the crater rim. Continued growth of the intracrater lava
dome was either recognized or assumed. Ibu lacked a working seismic
instrument. Its hazard status remained at Level II (Yellow, a condition
meaning 'caution or on guard' ('waspada' in Indonesian).
Our last few reports discussed mild ash explosions in 1999 (Bulletin v. 24,
no. 5), thermal alerts during 28 May-3 October 2001 and the fact that
activity during much of 2002 was likely just below the detection threshold
(Bulletin v. 28, no. 3).
Background. The truncated summit of Gunung Ibu stratovolcano along the NW
coast of Halmahera Island has large nested summit craters. The inner
crater, 1 km wide and 400 m deep, contained several small crater lakes
through much of historical time. The outer crater, 1.2 km wide, is breached
on the N side, creating a steep-walled valley. A large parasitic cone is
located ENE of the summit. A smaller one to the WSW has fed a lava flow
down the western flank. A group of maars is located below the northern and
western flanks of the volcano. Only a few eruptions have been recorded from
Ibu in historical time, the first a small explosive eruption from the
summit crater in 1911. An eruption producing a lava dome that eventually
covered much of the floor of the inner summit crater began in December 1998.
Information Contacts: Directorate of Volcanology and Geological Hazard
Mitigation (DVGHM), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL:
www.vsi.dpe.go.id/).
Kavachi
Solomon Islands
9.02°S, 157.95°E; summit elev. -20 m (submarine)
All times are local (= UTC + 11 hours)
The Solomon Islands' goverment-supported web service, the People First
Network (PFnet) reported in March 2004 that Corey Howell of The Wilderness
Lodge, Gatokae Island, observed Kavachi erupting (figure 8). Kavachi is
among the world's few regularly erupting submarine volcanoes that sends
material above the ocean surface in witnessed (and reported) eruptions.
Figure 8. A photo of Kavachi erupting as seen on 15 March 2004. The
original caption on PFnet was "Kavachi awoke on Monday in spectacular
fashion after an eight-month slumber . . .." Courtesy of Corey Howell.
The figure caption on PFnet notes an 8-month period of Kavachi inactivity,
which was also confirmed in brief correspondence with Howell. A report that
summarized the interval between the summer of 2001 and the end of 2003
(Bulletin v. 29, no. 1) lacked any mention of an eruption during mid-August
2003, eight months before the recent eruption.
Background. Kavachi, one of the most active submarine volcanoes in the SW
Pacific, occupies an isolated position in the Solomon Islands far from
major aircraft and shipping lanes. Kavachi, sometimes referred to as Rejo
te Kvachi ("Kavachi's Oven"), is located S of Vangunu Island only about 30
km N of the site of subduction of the Indo-Australian plate beneath the
Pacific plate. The shallow submarine basaltic-to-andesitic volcano has
produced ephemeral islands up to 1 km long many times since its first
recorded eruption during 1939. Residents of the nearby islands of Vanguna
and Nggatokae (Gatokae) reported "fire on the water" prior to 1939, a
possible reference to earlier submarine eruptions. The roughly conical
volcano rises from water depths of 1.1-1.2 km on the N and greater depths
to the S. Frequent shallow submarine and occasional subaerial eruptions
produce phreatomagmatic explosions that eject steam, ash, and incandescent
bombs above the sea surface. On a number of occasions lava flows were
observed on the surface of ephemeral islands.
Information Contacts: Corey Howell, The Wilderness Lodge, P.O. Box 206,
Homiara, Solomon Islands (Email: peava@thewildernesslodge.org; URL:
www.thewildernesslodge.org/); People First Network (PFnet), Rural
Development Volunteers Association, Ministry of Provincial Government and
Rural Development, PO Box 919, Honiara, Solomon Islands (Email:
pfnet@pipolfastaem.gov.sb; URL: www.peoplefirst.net.sb/).
Lopevi
Central Islands, Vanuatu
16.507°S, 168.346°E; summit elev. 1,413 m
All times are local (= UTC + 11 hours)
Previously, Bulletin reports for 2003 chiefly discussed either
aviation-related reports about ash plumes or satellite data, such as the
spectroscopic sensing of SO2 or infrared data in the form of MODVOLC
thermal alerts (Bulletin v. 27, no. 12; v. 28, nos. 1 and 6; v. 29, no. 6).
Since those reports more first-hand observations of conditions on the
ground have emerged regarding Lopevi during 2003. Numerous thermal
anomalies were detected by the MODIS satellite at Lopevi during July 2003
to March 2005 (table 2). Other observations also indicate activity
continuing in 2005. Lopevi erupts nearly continuously, but, because it is
an uninhabited island, activity often goes unreported.
Table 2. MODVOLC thermal anomalies as observed from the MODIS satellite for
Lopevi volcano for the period July 2003 to March 2005. The third column
gives the MODIS sensor that detected the hot spot; T = Terra-MODIS, and
A=Aqua MODIS. The fourth column shows radiance in watts per square meter,
per steradian, per micron (W m-2 sr-1 mm-1) in MODIS band 21 (central
wavelength of 3.959 mm). Courtesy of the Hawaiian Institute of Geophysics
and Planetology.
Date Time Sensor Spectral
(mo/dy/ yr) (UTC) radiance
02/16/2005 0245 A 2.813
02/05/2005 1355 A 0.983
02/05/2005 1355 A 1.426
01/30/2005 1130 T 0.710
01/03/2005 0220 A 2.560
12/15/2004 1115 T 3.425
11/18/2004 0210 A 2.771
11/13/2004 1115 T 0.886
10/04/2004 2300 T 3.009
09/28/2004 1410 A 0.937
09/28/2004 1410 A 1.052
09/17/2004 1125 T 1.123
09/10/2004 1115 T 1.186
08/07/2004 1130 T 1.015
07/19/2004 1400 A 0.362
07/07/2004 2305 T 2.883
05/28/2004 1125 T 1.797
05/28/2004 1125 T 3.012
05/12/2004 1425 A 1.353
05/12/2004 1125 T 2.332
04/22/2004 1150 T 0.930
04/17/2004 1130 T 0.949
03/27/2004 1415 A 2.314
03/27/2004 1415 A 0.740
03/02/2004 1120 T 1.636
02/28/2004 1350 A 0.965
02/28/2004 1350 A 1.017
02/17/2004 1410 A 1.218
02/01/2004 1405 A 0.917
01/15/2004 0230 A 4.117
11/02/2003 1125 T 1.154
11/02/2003 1125 T 2.527
10/08/2003 1130 T 2.212
10/04/2003 0225 A 3.680
09/02/2003 0225 A 3.815
08/21/2003 1130 T 2.143
08/18/2003 1400 A 0.917
08/16/2003 1410 A 1.100
Lopevi remains a danger for the region, and particularly for Paama Island,
the closest inhabited island (6 km away). The explosive eruption of 2001
turned day into night for several hours, and the ashfall polluted the
islanders' water supply to the point where the Australian Navy had to send
a ship to bring residents drinking water. Since then, wells equipped with
hand-operated pumps have been installed on Paama's N side, the flank
threatened most directly. Lardy suggested that evacuating 1,633 inhabitants
(the number cited in a 1999 census) is not realistic, but that the
population could be supplied with dust-filtering face masks prior to the
next eruption. The majority of Paama Island residents live on the W coast
and even for the closest residents on Paama's N coast, the view of Lopevi
is often limited.
Observations during 2003. Michel Lardy summarized the activity during 2003.
The major volcanic events of June 2001 (Bulletin v. 26, no. 8) and of June
2003 (Bulletin v. 28, no. 6) appear to have originated at the adventive
crater and through fractures in the island's N and W sides (figures 9 and
10). In particular, vents on the N, NW, and W opened in 2001 and 2003. Vent
opening in 2001 occurred at 16° 31.879' S, 168° 19.846 E. A 2001 lava flow
was prominent on the N flank. Radar interferometry depicted lava in 2001 on
the volcano's N side, in the crater, and at several places on the N and W
flanks.
Figure 9. Lava flows down Lopevi's N flank and entering the sea during
June(?) 2003. Note multiple lava flows, distinct vent areas, and the
presence of at least two active points of entry into the ocean at the time
of the photo. Photo credit, Shane Cronin (Massey University).
Figure 10. A closer look at the vents feeding lava flows down Lopevi's N
flank during June(?) 2003. The vents formed along radial fractures. Photo
credit, Shane Cronin (Massey University).
Observations during 2004. During September 2004 thermal anomalies were
detected four times, as many times as any month during the interval shown
on table 2. However, none of the 28 September anomalies were unusually
strong (~1 W m^-2 sr^-1 mm^-1) and the spectral radiance of some other
observations were several-fold larger (up to ~3.8 W m^-2 sr^-1 mm^-1).
Volcano tour guide John Seach visited SE Ambrym volcano in November 2004.
At that time he received reports from residents about previously unreported
eruptions of Lopevi that occurred during 2004. Specifically, during
September 2004, five large booming noises were heard coming from Lopevi by
villagers in S Ambrym. Explosions were separated by 2 minutes. The next day
there was ashfall on N and W Ambrym.
Observations during 2005. According to Seach, local observers in Vanuatu
indicated ongoing eruptive activity at Lopevi beginning at the end of
January 2005 and continuing into February.The Wellington VAAC is the key
group providing aviators with reports on Lopevi eruptions and ash plumes.
Their website posted all Volcanic Activity Advisories during 90 days prior
to 28 March, but there were no reports for Lopevi during that interval.
This absence of reports could be for a variety of reasons, such as
relatively few if any plumes during that interval. Other reasons might also
include extensive weather clouds screening satellite and pilot
observations, or an absence of reports from pilots or people in the field
to pass observations to the VAAC.
On 21 March 2005 IRD staff members observed Lopevi in usually clear weather
conditions (figures 11 and 12). These two photos highlight Lopevi's summit
crater and its off-axis NW-flank (adventive) crater. The adventive crater
has been a feature of the edifice since the early 1960s (Bulletin v. 24,
nos. 2 and 7; the latter issue contains a map showing the then-recent crater).
Figure 11. Annotated, N-looking view of Lopevi showing summit crater and
adventive crater, and two other islands in the background. Copyrighted
photo taken 21 March 2005 by P. Bani, IRD.
Figure 12. A photo of Lopevi's adventive NW-flank crater taken looking S
from an altitude of ~ 1 km. White deposits occur along considerable
portions of the larger crater's rim. The color version of this photo
indicates a yellow region lies on the internal crater (the crater inside
the larger crater and in the middle of the photo). Other areas of yellow
color were also visible farther to the right, although in this shot it was
masked by a hazy plume. The yellow color was attributed to sulfur deposits.
Copyrighted photo taken 21 March 2005; provided courtesy of M. Lardy, IRD.
The close-up photo (figure 12) shows a circular fracture along the crater's
rim and circumferential fractures along its walls, probably the result of
subsidence caused by the constant release of gas from the magma reservoir.
White hydrothermal deposits were thought to have been associated with this
gas release. The observers also saw yellow sulfur deposits near the
internal crater and between it and the northern rim (to the right on the
photo).
The perpendicular fractures visible just outside the crater (bottom center
on the photo) were also judged most likely related to this subsidence
associated with gas release. The small inner crater was a zone of active
deposition (building up that crater). This pattern, apparently cyclical,
has been visible since 1998, when Lopevi resumed an active phase following
a quiet period of about fifteen years during which only fumaroles were
observed. The summit crater (1,367 m elevation, figure 12) appears little
changed when compared with the same crater 1995 photos taken in 1995. The
major volcanic events of June 2001 (Bulletin v. 26, no. 8) and of June 2003
(Bulletin v. 28, no. 6) originated in the adventive crater and through
fractures in the island's N and W sides.
Lardy also commented that "observations made since the 19th century suggest
an activity cycle of 15 to 20 years, yet it remains difficult to forecast
the occurrence of major eruptive phases within the cycle. Although there
appears to be a recurrence of events in the month of June, it would be rash
to attempt to predict the next eruption given the current state of our
knowledge. Since November 2004, a micro-barometer has been set up on Paama
Island. It is connected to the SSI network (which monitors compliance with
the international ban on nuclear explosions) and has been recording the
explosive volcanic events occurring on Lopevi and Ambrym Islands. Real time
measurements should complement this monitoring system."
Reference: Le Pichon, A., and Drob, D., 2005, Probing high-altitude winds
using infrasound from volcanoes: Jour. of Geophys. Res. (in press)
Background. The small 7-km-wide conical island of Lopevi is one of
Vanuatu's most active volcanoes. A small summit crater containing a cinder
cone is breached to the NW and tops an older cone that is rimmed by the
remnant of a larger crater. The basaltic-to-andesitic volcano has been
active during historical time at both summit and flank vents, primarily
along a NW-SE-trending fissure that cuts across the island, producing
moderate explosive eruptions and lava flows that reached the coast.
Historical eruptions at the 1,413-m-high volcano date back to the mid-19th
century. The island was evacuated following eruptions in 1939 and 1960. The
latter eruption, from a NW-flank fissure vent, produced a pyroclastic flow
that swept to the sea and a lava flow that formed a new peninsula on the W
coast.
Information Contacts: Michel Lardy and Philipson Bani, Institut de
Recherche pour le developpement (IRD), CRV, BP A 5 Noumea, New Caledonia
(E.mail Michel.Lardy@noumea.ird.nc, Philpson.Bani@noumea.ird.nc); Morris
Harrison, Department of Geology, Mines, and Water Resources, PMB 01,
Port-Vila, Vanuatu (E.mail: observatoire@vanuatu.com.vu; URL:
www.mpl.ird.fr/suds-en-li....htm#suds);
Shane Cronin, Soil and Earth Sciences Group, Institute of Natural
Resources, Massey University, Private Bag 11 222, Palmerston North, New
Zealand (Email: S.J.Cronin@massey.ac.nz; John Seach, PO Box 16, Chatsworth
Island, NSW 2469, Australia (Email: john@volcanolive.com,
jseach@hotmail.com, URL: www.volcanolive.com/); Hawai'i Institute of
Geophysics and Planetology, University of Hawaii and Manoa, 168 East-West
Road, Post 602, Honolulu, HI 96822 (URL: modis.higp.hawaii.edu);
Wellington Volcanic Ash Advisory Center (VAAC), MetService, PO Box 722,
Wellington, New Zealand (URL: www.metservice.co.nz/).
__________________________________________________________
Global Volcanism Program, NHB E-421 Tel: (202) 633-1800
Smithsonian Institution Fax: (202) 357-2476
Washington, DC 20560-0119 Email: gvp@si.edu
Internet: www.volcano.si.edu/
-
Re: GVN Bulletin
Fri, June 10, 2005 - 11:14 PM*****************************************************
Bulletin of the Global Volcanism Network, April 2005
*****************************************************
From: Ed Venzke <venzke@volcano.si.edu>
Bulletin of the Global Volcanism Network
Volume 30, Number 4, April 2005
Lascar (Chile) 4 May 2005 eruption sends ash over 1,000 km SE, 3/4 of the
way to Buenos Aires
Fernandina (Galapagos Islands) Lava flows down S flank from circumferential
vents near caldera rim
Anatahan (Mariana Islands) Explosive eruption on 6 April 2005 issues
highest ash plume recorded here
Vailulu'u (Samoa) ALIA cruise discloses new cone in the summit crater
Awu (Indonesia) Stable during mid- to late August 2004
Karthala (Comoros) 16 April 2005 seismicity leading to eruption;
near-source tephra 1.5 m thick
Ol Doinyo Lengai (Tanzania) Tall hornito almost reaches summit elevation;
more lava spills over rim
Editors: Rick Wunderman, Edward Venzke, and Gari Mayberry
Volunteer Staff: Robert Andrews, Catherine Galley, William Henoch, Clement
Pryor, Steven Bentley, and Jerome Hudis
Lascar
northern Chile
23.37°S, 67.73°W; summit elev. 5,592 m
All times are local (= UTC - 3 hours)
Lascar, the most active volcano in northern Chile, erupted on 4 May 2005.
Although the eruption was substantial, thus far there is an absence of
reports from anyone who saw the eruption at close range. Preliminary
assessments came mainly from satellite sensors and distant affects
witnessed in Argentina. This report is based on one sent to us by Chilean
Observatorio Volcanologico de los Andes del Sur (OVDAS) scientists Jose
Antonio Naranjo and Hugo Moreno, discussing events around 4 May, with brief
comments on some of Lascar's behavior in the past several years, and
suggestions for future monitoring.
Lascar sits ~70 km SW of the intersection between Chile, Argentina, and
Bolivia, ~300 km inland from the Chilean port city of Antofagasta. This
part of the coast lies along the Atacama desert, and on flat terrain tens
of kilometers W of Lascar resides a large salt pan, the Salar de Atacama
(about 50 x 150 km). The settlement of Toconao is ~33 km NW of Lascar.
Previous reports discussed field observations during 13 October 2002 to 15
January 2003, and fine ash discharged from fumaroles on 9 December 2003
(Bulletin v. 28, no. 3, and v. 29, no. 1).
Naranjo and Moreno concluded that at roughly 0400 on 4 May an explosive
eruption ejected an ash cloud to a tentative altitude on the order of 10 km
that dispersed to the SE. About 2 hours later the cloud began dropping ash
on Salta, Argentina. Satellite images portrayed the ash cloud's dispersal.
An aviation 'red alert' was issued by the Buenos Aires Volcanic Ash Center;
they saw the plume over Argentina at altitudes of 3-5 km.
Shortly after atmospheric impacts of the 4 May eruption became apparent,
the Buenos Aires VAAC notified OVDAS that NW Argentine cities had reported
falling ash. These cities, all SE of Lascar, included Jujuy, Salta,
Santiago del Estero, and Santa Fe-locations with respective approximate
distances from Lascar of 260, 275, 580, and 1,130 km. The Argentine
province of Chaco, along the country's NE margin, was also noted as
receiving ash. Buenos Aires (~1,530 km SE of Lascar) remained ~400 km
beyond the point of the farthest detected ashfall.
Patricia Lobera, a professor in Talabre, Argentina, 17 km E of Lascar, said
that eruption noises were not heard there on the morning of 4 May. When
observers saw the plume from Talabre that morning they reportedly thought
the plume looked similar to those on previous days.
Remotely sensed hot spots were detected on a GOES satellite image for 0339
(0639 UTC) on 4 May, showing the first evidence of an eruption. In a later
image, at 0409, the thermal anomaly had increased, and the image suggested
a growing, ash-bearing cloud then trending ~23 km to the SE. The thermal
anomaly diminished in intensity by 0439, remaining diminished thereafter,
but by that time the plume's leading margin extended over ~100 km SE and
its tail had detached from the volcano. At 0509 the plume reached 170 km
SE. According to a press report, at around 0600 ash fell in Salta (~275 km
SE of Lascar).
Rosa Marquilla, a geologist at the University of Salta, reported that
residents there noticed a mist attributed to the eruption, which hung over
the city until at least to 1600, after which, the sky gradually cleared.
Preliminary description of the petrography of the ash that fell in Salta
came from Ricardo Pereyra (University of Salta) who saw crystal fragments
(pyroxenes, feldspars, and magnetite) and fragments of volcanic glass
containing plagioclase mircrolites. Lithic fragments were not observed.
The OVDAS authors concluded that, apparently since the year 2000, Lascar
underwent constant degassing from an open vent within the ~780-m-diameter
active central crater. Sporadic explosions as in July 2000 and October
2002, and in this case, 4 May 2005, could be due to diverse causes. For
example, there may have been temporarily obstructed conduits at depth,
local collapses blocking the vent at the crater floor, or fresh magma
injection contacting groundwater. Extrusion of a viscous dome lava also
might explain the sudden explosions. That circumstance would presumably
lead to visibly increased fumarolic output.
Naranjo and Moreno had several suggestions for ongoing monitoring. First,
they suggested developing closer long-term contacts, including people able
to visually monitor the volcano directly, as well as continued systematic
contact with the Buenos Aires VAAC and their satellite analysts. They
recommended ongoing relations with the University of Hawaii (MODVOLC)
program to remotely sense hot-spots. They went on to suggest a campaign of
stereo aerial photography to detect changes in the active crater. They
advocated notifying local inhabitants of the possibility of ash falls
before another explosive episode. They pointed out that mountaineers should
be made aware of elevated risks within 8 km of the active crater.
Background. Lascar is the most active volcano of the northern Chilean
Andes. The andesitic-to-dacitic stratovolcano contains six overlapping
summit craters. Prominent lava flows descend its NW flanks. An older,
higher stratovolcano 5 km to the E, Volcan Aguas Calientes, displays a
well-developed summit crater and a probable Holocene lava flow near its
summit (de Silva and Francis, 1991). Lascar consists of two major edifices;
activity began at the eastern volcano and then shifted to the western cone.
The largest eruption of Lascar took place about 26,500 years ago, and
following the eruption of the Tumbres scoria flow about 9,000 years ago,
activity shifted back to the eastern edifice, where three overlapping
craters were formed. Frequent small-to-moderate explosive eruptions have
been recorded from Lascar in historical time since the mid-19th century,
along with periodic larger eruptions that produced ashfall hundreds of
kilometers away from the volcano. The largest historical eruption of Lascar
took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit
and ashfall in Buenos Aires.
References: Gardeweg, M., 1989, Informe preliminar sobre la evolucion de la
erupcion del volcan Lascar (II Region): noviembre 1989: Servicio Nacional
de Geologia y Mineria, Informe Inedito (unpublished report), 27 p.
Gardeweg, M., and Lindsay, J., 2004, Lascar Volcano, La Pacana Caldera, and
El Tatio Geothermal Field: IAVCEI General Assembly Pucon 2004, Field Trip
Guide-A2, 32 p.
Gardeweg, M., Medina, E., Murillo, M., and Espinoza, A., 1993, La erupcion
del 19-20 de abril de 1993: VI informe sobre el comportamiento del volcan
Lascar (II Region): Servicio Nacional de Geologia y Mineria, Informe
Inedito (unpublished report), 20 p.
Information Contacts: Jose Antonio Naranjo and Hugo Moreno, Programa Riesgo
Volcanico, Servicio Nacional de Geologia y Mineria, Avda. Santa Maria 0104,
Casilla 1347, Santiago, Chile; Gustavo Alberto Flowers, Buenos Aires
Volcanic Ash Advisory Center (Buenos Aires VAAC), Servicio Meteorologico
Nacional-Fuerza Aerea Argentina, 25 de mayo 658, Buenos Aires, Argentina
(URL: www.meteofa.mil.ar/vaac/vaac.htm).
Fernandina
Galapagos Islands, Ecuador
0.37°S, 91.55°W; summit elev. 1,476 m
All times are local (= UTC - 6 hours)
On the morning of 13 May 2005, a new eruption started on uninhabited
Fernandina volcano (figure 1). Fernandina last erupted in 1995 (figure 2),
and had been quiet and seemingly unchanged when a team from the Ecuadorian
Institute of Geophysics (IG) flew over it in late March 2005. On 11 May an
M 5.0 earthquake occurred with an epicenter ~30 km E of Fernandina's
center. Only two other earthquakes have been located by the U.S. Geological
Survey (USGS) within 100 km of Fernandina in last 4.5 years (M 4.0 on 23
February 2005 and M 4.6 on 16 April 2005), both having epicenters ~70-80 km
SE of Fernandina's center. A seismic station, installed by the IG in 1996
on the NE coast of the island, was out of service at the time of eruption.
Figure 1. Sketch map of Fernandina, showing the conspicuous summit caldera,
and indicating the flow fields and circumferential vent area from the 13
May 2005 eruption (as mapped on 14 May by airborne reconnaissance
and reported by the Charles Darwin Research Station). Key features
include the active circumferential fissure vent and two main areas impacted
by lava flows. The eastern area contained lava flows still mobile on 14
May; flows to the W had already cooled by 14 May.
On the index map of the Galapagos Islands, the largest island, Isabela, is
~ 130 km long and lies to the E of Fernandina island. "La Cumbre"-Spanish
for the summit, peak, or top-has been mistakenly applied to the volcano,
apparently because the summit was so labeled on an old map. The island has
also been called Narborough. The index map is incomplete in its portrayal
of both volcanoes and islands of the archipelago. Revised from Bulletin v.
20, no. 1.
Galapagos National Park workers in western Galapagos were apparently the
first to witness the eruption, and IG technicians recognized it on
satellite imagery. The University of Hawaii presents hotspot images on
their website. Their GOES data lacked hotspots at 0930, but a clear and
strong one had developed on the S flank by 0945. Francisco Dousdebes (of
Metropolitan Touring) placed the eruption's start time at 0935. S-flank
hotspots were comparatively extensive by 1015. The Washington VAAC issued
their first full advisory at 1315. Their notices reported that the
W-directed plume rose to ~5 km altitude, and the S-directed plume went to 9
km; both were visible as late as 1745 on 13 May, depicting the leading
portions of Fernandina' s ash plume more than 200 km from the volcano
An overflight of the eruption on the 13th by the National Park resulted in
a report by Patricio Ramon and Hugo Yepes, and the eruption was confirmed
by Washington Tapia, director of the Galapagos National Park. That evening,
Galapagos resident Greg Estes telephoned Dennis Geist to report that the
eruptive source was a "circumferential vent near [the] summit, S side . . .
6 km long with an eruptive zone 50 m across." It was uncertain how this
fissure was related to the 1981 eruption site (figure 2 and Bulletin v. 9,
no. 3). IG also noted that tephra had fallen on neighboring Isabela Island,
in the areas of the volcanoes Wolf and Ecuador (~40 km from the vent,
figure 1).
Figure 2. A 2002 International Space Station photograph of Fernandina,
looking obliquely towards the E (N is towards the left). Labels show key
features developed in 1995, 1981, and 1968 eruptions. Note the island's
coastline in the lower-right corner and along much of the left margin.
Despite the steep walls bounding the 850 m deep, 5 x 6.5 km central
caldera, it supports both animal and plant populations. Image ISS05E06997
(Visible Earth v1 ID 18002) with contrast enhanced and labels added by
Bulletin editors.
At 0537 on the second morning, 14 May, the Washington VAAC reported low
level ash/steam not visible in infrared imagery, but at 0746, 1½ hours
after sunrise, a plume of ash extended ~130 km to the W and was moving at
18 km/hour at 1,800 m elevation. The GOES thermal anomaly was greatly
diminished by 0930, and remained low to non-existent until resumption
around 1415. That afternoon, an overflight by Godfrey Merlen, Wacho Tapia,
and Alan Tye (Charles Darwin Research Station) resulted in the fullest
report to date.
They said that although the vent area was obscured by clouds, topography
suggested a 4.5 km long fissure vent near the S rim, with activity having
progressed from SW (near the first and uppermost flows of the 1995 radial
fissure eruption) to the E (figure 1). The lava flows "had begun to pond on
the gentler outer skirt of the island," and were then 5.5 km from the coast
(~5 km from the vents). They thought it unlikely that the flows would reach
the sea. A follow-up news report in El Comercio (Quito) quoted Tapia as
identifying five flows down the S flank. Only one remained incandescent. At
1745 on 14 May, Washington VAAC reported a plume remaining to the NW,
but-lacking detectable ash-they discontinued advisories. Thermal anomalies
on the GOES satellite remained strong, however, until the next morning.
The report also noted that, "As on previous eruptions, such as that on
Cerro Azul in 1998, lava passing through vegetated areas has caused small
fires, but these have not spread far from the lava tongues themselves
before going out. Most of the new flows have passed over unvegetated older
lava, and damage to Fernandina's vegetation is limited."
The team also flew over Alcedo volcano on Isabela, where Project Isabela
staff had reported increased fumarole activity. Steam was rising from the
"new" fumarole sites (active since the 1990s) and from the area of sulfur
deposits and fumaroles in the southwestern area of the rim, but this
activity did not appear unusual.
On 15 May, the GOES thermal anomaly was gone before noon, but returned near
midnight (about 2330), over a smaller area, and it remained through sunrise
(0615) on 16 May. Small anomalies were visible the next several nights
(when contrast with adjacent cold flows was strongest), but there was no
obvious evidence of continued feeding of the new flows.
The complex thermal anomalies detected in MODIS satellite imagery (provided
by the University of Hawaii), were abundant around the time of eruption.
They spread over Fernandina's rim, in some cases in the caldera, and
broadly over the S flank. They continued through at least the rest of May.
The Washington VAAC reported that a weak hotspot started 29 May 2005 at
1945 (30 May at 0145 UTC) and a very short narrow plume of ash and gases
appeared in multi-spectral imagery at 2145 (30 May at 0345 UTC). No ground
confirmation of an eruption was available, and there was a layer of
low-level weather cloud over the island. At that time, the plume appeared
to dissipate as it moved away at ~18 km/hour.
Background. Fernandina, the most active of Galapagos volcanoes and the one
closest to the Galapagos mantle plume, is a basaltic shield volcano with a
deep 5 x 6.5 km summit caldera. The volcano displays the classic
"overturned soup bowl" profile of Galapagos shield volcanoes. Its caldera
is elongated in a NW-SE direction and formed during several episodes of
collapse. Circumferential fissures surround the caldera and were
instrumental in growth of the volcano. Reporting has been poor in this
uninhabited western end of the archipelago and even a 1981 eruption was not
witnessed at the time. In 1968 the caldera floor dropped 350 m following a
major explosive eruption. Subsequent eruptions, mostly from vents located
on or near the caldera boundary faults, have produced lava flows inside the
caldera as well as those in 1995 that reached the coast from a SW-flank
vent. Collapse of a nearly 1 km³ section of the E caldera wall during an
eruption in 1988 produced a debris-avalanche deposit that covered much of
the caldera floor and absorbed the caldera lake.
Information Contacts: Patricio Ramon and Hugo Yepes, Geophysical Institute
(IG), Escuela Politecnica Nacional, Apartado 17-01-2759, Quito, Ecuador
(URL: www.igepn.edu.ec/); Alan Tye, Charles Darwin Research Station,
Puerto Ayora, Santa Cruz, Galapagos Islands, Ecuador (URL:
www.darwinfoundation.org/); Washington Volcanic Ash Advisory Center
(VAAC), Satellite Analysis Branch, NOAA/NESDIS E/SP23, NOAA Science Center
Room 401, 5200 Auth Road, Camp Springs, MD 20746 USA (URL:
www.ssd.noaa.gov/); Tom Simkin, Dept. of Mineral Sciences, National
Museum of Natural History, Smithsonian Institution, Washington, DC
20013-7012, USA (Email: simkin@nmnh.si.edu); National Earthquake
Information Center, U.S. Geological Survey, Box 25046, DFC, MS 966, Denver,
CO 80225-0046, USA (neic.usgs.gov/); MODIS Thermal Alert System;
University of Hawaii and Manoa, 168 East-West Road, Post 602, Honolulu, HI
96822, USA (URL: modis.higp.hawaii.edu).
Anatahan
Mariana Islands, USA
16.35°N, 145.67°E; summit elev. 788 m
All times are local (= UTC + 10 hours)
Anatahan's third historical eruption began on 5 January 2005, and is
described in Bulletin v. 29, no. 12. Further details and satellite images
were presented in Bulletin v. 30, no. 2, which covered events until
mid-February 2005. A 5-6 April 2005 eruption cloud rose to at least 15 km
altitude, which was the highest yet seen at the volcano.
Anatahan erupted almost continuously after 5 January 2005, when it started
its third eruption in recorded history. An image collected by the Ozone
Monitoring Instrument on NASA's Aura satellite shows atmospheric sulfur
dioxide (SO2) concentrations between 31 January and 4 February 2005 (figure
3). A long SO2 plume extends NE and SW of Anatahan, and the edge of the
plume covers Guam (the southernmost island) and the other Mariana Islands
immediately to Anatahan's N and S.
Figure 3. Anatahan's atmospheric SO2 as imaged by Aura's OMI instrument on
31 January 2005. The OMI (Ozone Monitoring Instrument) measures SO2 in
Dobson Units. Dobson Units, which derive from spectroscopic measurement
techniques, can be thought of as the mass of molecules per unit area of
Earth's atmospheric column. One Dobson Unit equals 0.0285 grams of SO2 per
square meter. The Ozone Monitoring Instrument (OMI) that created this image
tracks global ozone change and monitors aerosols like sulfates in the
atmosphere. It was added to the Aura satellite as part of a collaboration
between the Netherlands' Agency for Aerospace Programs and the Finnish
Meteorological Institute. NASA describes the Eos system Aura as "A mission
dedicated to the health of the Earth's atmosphere." NASA image courtesy
Simon Carn (Joint Center for Earth Systems Technology (JCET), University of
Maryland Baltimore County (UMBC)).
Volcanogenic SO2 combines with water to create a sulfuric acid haze. Called
"vog," this haze can cause illness and make breathing difficult. Volcanic
haze grew so thick during the first week of February that the National
Weather Service issued a volcanic haze advisory for Guam, where several
illnesses were reported.
After mid-February 2005, eruptive activity at Anatahan steadily declined to
less than 5% of the peak level attained since the eruption started on 5
January. Ash eruptions continued, and the 2003 crater floor was almost
entirely covered by fresh lava out to a diameter of ~1 km. A MODIS image
taken at 0115 on 18 February showed a plume of steam and vog extending
about ~170 km SW of Anatahan. Seismic and acoustic records during the last
week of February 2005 showed very low levels of activity. Seismic
amplitudes during 23-28 February were similar to those recorded prior to
the 5 January eruption. NASA MODIS (Moderate Resolution Imaging
Spectroradiometer) imagery taken on 28 February showed a faint plume of vog
and steam trending W of Anatahan.
During the first two weeks of March 2005 volcanic and seismic activity
increased relative to the previous weeks. During 14-17 March, seismicity
increased and steam rose a few hundred meters above the volcano. The inner
E crater had been nearly filled with lava flows and lapilli since early
January.
A small eruption began on 18 March at 1544 according to seismic data. On 19
March the Washington VAAC issued an advisory that an ash plume was visible
on satellite imagery below 4 km altitude. Small explosions that began late
on 20 March lasted for 14 hours. No emissions were visible on satellite
imagery, but others were, later in March and April.
A strong outburst apparently began on 21 March, a day when seismicity
increased significantly. Seismic amplitudes peaked on the 25th and faded
out on the 26th. Near the peak on the 25th, the U.S. Air Force Weather
Agency (AFWA) detected a hot spot on the island on satellite imagery and
reported an ash plume briefly reaching ~5.8 km altitude. The plume height
soon dropped to below 3 km altitude, and by near midday on the 27th the
plume had changed from ash and steam to steam and vog. On the 27th the
plume extended ~240 km SW.
On 5 April at about 2200 seismic signals began to increase slowly, and the
Washington VAAC began to see increased ash on satellite imagery. On 6 April
2005 around 0300 an explosive eruption began and produced an ash plume to
an initial height of ~15.2 km altitude, the highest in recorded history
from the volcano. Seismicity peaked at the same time.
The AFWA reported an upper level ash plume at ~15.2 km altitude blowing E
to SE and a lower level ash plume at ~4.6 km altitude blowing SW; the upper
plume extended more than 465 km. Earth Probe TOMS data on 6 April at 1046
showed a compact sulfur-dioxide cloud drifting E of Anatahan following the
eruption.
Chuck Sayon, the superintendent of American Memorial Park noted, "On Saipan
at around 10 AM the skies darkened and light ash started falling . . . park
operation[s] have been restricted to indoor activities due to irritation to
eyes and breathing as ash starts to lightly coat the area. Schools are
closed as well as the airport until further notice . . .."
On 6 April during 0400 to 0900 the seismicity at Anatahan decreased to near
background. The seismicity surged for about 1 hour, with amplitudes about
one-half those reached during the earlier eruption, and subsequently
dropped again to near background. Prior to the 6 April eruption, during 31
March to 4 April the amplitudes of harmonic tremor varied, reaching a
2-month high on the 3rd. Small explosions occurred every one minute to
several minutes, probably associated with cinder-cone formation.
Steam-and-ash plumes drifted ~200 km, and vog drifted ~400 km at altitudes
below ~2.4- 4.6 km.
The U.S. Geological Survey (USGS) (in conjunction with the Commonwealth of
the Northern Mariana Islands) stated that the "eruption of 6 April 2005 was
the largest historical eruption of Anatahan and expelled roughly 50 million
cubic meters of ash. The eruption column and the amplitude of harmonic
tremor both grew slowly over about 5 hours and both peaked about 0300 on 6
April local time . . .. The peak of the eruption lasted about one hour and
then the activity declined rapidly over the following hour."
The 6 April 2005 eruption's plume was captured on satellite images. The
image showed a plume that was tan or brown in color and clearly ash laden
(figure 4).
Figure 4. A major eruption from Anatahan on 6 April 2005 sent an ash plume
to ~ 15 km. The eruption was considered the largest since Anatahan's first
recorded eruption on 10 May 2003. This Moderate Resolution Imaging
Spectroradiometer (MODIS) image was acquired by NASA's Terra satellite at
0035 UTC, about 8 hours after the eruption began. By this time, the ash
plume had spread S to entirely cover Saipan and Tinian, islands immediately
to the S. Courtesy of the MODIS Rapid Response Image Gallery, sponsored in
part by NASA.
Figure 5 shows SO2 concentrations in the atmosphere on 7 April 2005, over
30 hours after the large 6 April eruption. SO2 emissions from the eruption
were measured by the Ozone Monitoring Instrument (OMI) on NASA's EOS/Aura
satellite. OMI detects the total column amount of SO2 between the sensor
and the Earth's surface and maps this quantity as it orbits the planet. A
new perspective on the vertical distribution of the SO2 is revealed by
combining the OMI data with coincident measurements made by the Microwave
Limb Sounder (MLS), also part of the Aura mission.
Figure 5. Anatahan's 5-6 April 2005 eruption injected significant SO2 high
into the atmosphere. This OMI image depicts the concentrations found over
30 hours after the eruption, a time when the SO2 formed two separate zones
at distance from the source. Analysis suggests that the westerly zone of
SO2 was probably in the lower troposphere and the eastern zone was probably
in the upper troposphere or above. Courtesy of Simon Carn.
The MLS data crisscross the OMI image and clearly show that some, but not
all, of the SO2 measured by OMI to the volcano's E was in the upper
troposphere or above. At these altitudes, SO2--and the sulfate aerosols
that form from it--can stay in the atmosphere and affect the climate for a
longer period of time. A weaker SO2 signal was also measured in the same
region during the nighttime MLS overpass, which crosses the image from
upper right to lower left. The daytime data, running from upper left to
lower right, coincide with the OMI measurements. The MLS data west of
Anatahan show no significant SO2 signal, indicating that the SO2 measured
by OMI in this region was in the lower troposphere.
MLS measures thermal emissions from the Earth's limb, so unlike the OMI
sensor it also collects data at night. It is designed to measure vertical
profiles of atmospheric gases that are important for studying the Earth's
ozone layer, climate, and air quality, such as SO2. These images, derived
from preliminary, unvalidated OMI and MLS data, show MLS SO2 columns
(filled circles) measured every 165 km along the Aura orbit, plotted over
the OMI SO2 map. The MLS SO2 columns shown here are derived from profile
measurements made from the upper troposphere into the stratosphere (~215-0
hPa (hectoPascal, 10^2 Pa) or ~12 km altitude and above), and the circles
do not represent the actual size of the MLS footprint, which is roughly 165
x 6 km.
Anatahan's morphological changes were highlighted in before (pre-eruption)
versus after (post-eruption) images. Seismicity decreased at Anatahan after
6 April and during 7-11 April was at very low levels, near background. On
11 April, a steam-and-ash plume rose ~2.7 km altitude and drifted ~280 km WSW.
Occasional data from Anatahan revealed that seismicity appeared to increase
during 24-25 April. During 20-25 April, a continuous thin plume of
ash-and-steam rose to less than ~3 km altitude and drifted more than 185 km
from the volcano. Harmonic tremor dropped dramatically on 1 May after being
at high levels for several days. During 27 April to 1 May, the main
ash-and-steam plume rose to ~3 km altitude According to a news article, the
volcanic plume from Anatahan reached Philippine airspace on 4 May.
On 5 May an extensive ash-and-steam plume to 4.5 km altitude was visible in
all directions. Ash extended 770 km N, 130 km S (to northern Saipan), and
110 km W. Vog extended in a broad swath from 3,000 km W, over the
Philippines, to 1,000 km N of Anatahan. By 9 May harmonic tremor amplitude
had decreased to near-background levels, with a corresponding drop in
eruptive activity. As of 10 May AFWA was reporting ash to about 3 km
altitude extending 400 km W and an area of vog less than half that noted on
5 May.
On 11 May AFWA reported thick ash rising to 4.2 km altitude and moving WNW.
The thick ash extended in a triangular shape from the summit 444 km to the
WSW through 510 km to the NW. A layer of thin ash at 3 km altitude extended
another 1,000 km beyond the thick ash. A broad swath of vog extended over
2,200 km W nearly to the Philippines and over 1,400 km NNW of Anatahan.
Although the ash plume diminished over the next few days and was not as
thick, it remained significant, rising to 2.4 km and extending 370 km WNW
on the 13th. Scientific personnel from the Emergency Management Office and
the USGS working the next day at a spot 2-3 km W of the active vent heard a
continuous roaring sound. They also saw ash and steam rising by pure
convection, not explosively, to 3 km altitude.
Background. The elongated, 9-km-long island of Anatahan in the central
Mariana Islands consists of two coalescing volcanoes with a 2.3 x 5 km,
E-trending summit depression formed by overlapping summit calderas. The
larger western caldera is 2.3 x 3 km wide and extends E from the summit of
the western volcano, the island's 788-m-high point. Ponded lava flows
overlain by pyroclastic deposits fill the caldera floor, whose SW side is
cut by a fresh-looking smaller crater. The summit of the lower eastern cone
is cut by a 2-km-wide caldera with a steep-walled inner crater whose floor
is only 68 m above sea level. Sparseness of vegetation on the most recent
lava flows on Anatahan indicated that they were of Holocene age, but the
first historical eruption of Anatahan did not occur until May 2003, when a
large explosive eruption took place forming a new crater inside the eastern
caldera.
Reference: Chadwick, W.W., Embley, R.W., Johnson, P.D., Merlea, S.G.,
Ristaub, S., and Bobbitta, A., 2005, The submarine flanks of Anatahan
volcano, Commonwealth of the Northern Mariana Islands: Jour. of Volcanology
and Geothermal Res. (In press, June 2005).
Information Contacts: Juan Takai Camacho and Ramon Chong, Emergency
Management Office of the Commonwealth of the Northern Mariana Islands
(CNMI/EMO), PO Box 100007, Saipan, MP 96950, USA (URL:
www.cnmiemo.org/; Email: juantcamacho@hotmail.com and
rcchongemo@hotmail.com); Simon Carn, Joint Center for Earth Systems
Technology (JCET), University of Maryland Baltimore County (UMBC), 1000
Hilltop Circle, Baltimore, MD 21250, USA; Hawaiian Volcano Observatory
(HVO), U.S. Geological Survey, PO Box 51, Hawaii National Park, HI 96718,
USA (URL: hvo.wr.usgs.gov/; Email: hvo-info@hvomail.wr.usgs.gov);
Charles Holliday, U.S. Air Force Weather Agency (AFWA), Offutt Air Force
Base, Nebraska 68113, USA (Email: Charles.Holliday@afwa.af.mil); Randy
White and Frank Trusdell, U.S. Geological Survey, 345 Middlefield Road,
Menlo Park, CA 94025-3591 USA (URL hvo.wr.usgs.gov/cnmi/update.html;
Email: rwhite@usgs.gov; trusdell@usgs.gov,); Saipan Tribune, PMB 34, Box
10001, Saipan, MP 96950, USA (URL: www.saipantribune.com/);
Operational Significant Event Imagery (OSEI) team, World Weather Bldg.,
5200 Auth Rd Rm 510 (E/SP 22), NOAA/NESDIS, Camp Springs, MD 20748, USA
(URL: www.osei.noaa.gov/, Email: osei@noaa.gov); Washington Volcanic
Ash Advisory Center (VAAC), Satellite Analysis Branch, NOAA/NESDIS E/SP23,
NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746 USA
(URL: www.ssd.noaa.gov/); Chuck Sayon, American Memorial Park,
Saipan, MP 96950, USA; NASA's Earth Observatory (URL:
earthobservatory.nasa.gov/).
Vailulu'u
Samoan Islands, USA
14.21°S, 169.06°W; summit elev. -590 m
According to Hubert Staudigel (Scripps Institution of Oceanography) and
Stanley Hart (Woods Hole Oceanographic Institute), Vailulu'u seamount, the
most active Samoan submarine volcano, erupted between April 2001 and April
2005. It formed a 293-m-tall lava cone, which was named Nafanua after the
Samoan Goddess of War. This new cone had been growing inside the 2-km-wide
caldera of Vailulu'u at a minimum rate of about 20 cm/day since April 2001.
Nafanua was discovered during a 2005 diving expedition with the National
Oceanic and Atmospheric Agency (NOAA) research submersible Pisces V,
launched from the University of Hawaii research vessel Kaimikai O Kanaloa
(KOK). It is located in the originally 1,000-m-deep W crater of Vailulu'u
(figures 6 to 9).
Figure 6. The route of the 2005 cruise of the research vessel Kilo Moana.
Vailulu'u, towards the E end of the Samoan hotspot trail was visited on
cruise days 1-4, 4-8 April 2005. Courtesy of H. Staudigel and S. Hart.
Figure 7. Bathymetry of Vailulu'u and nearby Ta'u Island, based on a
SeaBeam bathymetric survey performed during R/V Melville's AVON 2 and 3
cruises, augmented with satellite-derived bathymetry from Smith and
Sandwell (1996). The inset shows the general location of Vailulu'u with
respect to the Samoan Archipelago; two other newly mapped and dredged
seamounts (Malumalu and Muli, AVON 3 cruise) are shown as well. Scale: 10'
= 18 km. From Hart and others (2000).
Figure 8. Bathymetry of the Vailulu'u crater between the 1999 and 2005
surveys, showing the emergence of Nafanua. Courtesy of H. Staudigel and S.
Hart.
Figure 9. Bathymetric map of the Vailulu'u seamount from multibeam data
during the April 2005 survey. Note the new inner cone named Nafanua.
Contour interval is 20 m. Courtesy of H. Staudigel and S. Hart.
Seismic monitoring during April-June 2000 showed substantial seismicity, ~4
earthquakes per day with hypocenters beneath Nafanua (Konter and others,
2004; Bulletin v. 26, no. 6), which can now be interpreted as pre-eruption
seismic activity. These observations are consistent with previous reports
highlighting the volcanic and hydrothermal activity of Vailulu'u (Hart and
others, 2000; Staudigel and others, 2004). The scientists suggested that
continued volcanic activity could bring the summit region of Vailulu'u to a
water depth of ~200 m. At that point, Nafanua would overtop the crater rim
and further growth would require a build-up of the lower flanks, areas that
rise from the 5,000-m-deep floor of the ocean.
Staudigel and Hart teamed up in April 2005 on the Hawaiian Research Vessel
Kilo Moana to study the Samoan hotspot thought to underlie Vailulu'u. They
named their expedition ALIA after the ancient twin-hulled canoe that Samoan
warriors used to explore the SW Pacific. The Kilo Moana left Pago Pago on 4
April 2005 to study active and extinct underwater volcanoes along the chain
of Samoan islands. The expedition investigated previously uncharted
seamounts and the submarine portions of some islands, scattered over almost
600 nautical miles, from its most recent and quite active Vailulu'u
submarine volcano in the E to Combe Island in the W.
The Nafanua cone was first mapped by using the center beam of the research
vessel KOK in several crossings of the W crater. An active hydrothermal
system was apparent from evidence such as the murky water that limited
visibility during two submersible dives, several microbial biomats covering
pillow lavas that were centimeters thick, and a large number of diffuse
vents. A dive on 30 March 2005 to examine Nafanua reported "that it must
have grown in the last 4 years because CTD (conductivity-temperature-depth)
crossings in 2001 still were consistent with the old crater morphology ...
the basal portion of the cone displayed relatively large pillows, and
higher up pillows look almost like very fluid pahoehoe that collapsed
and/or transitioned into aa flows. Nafanua . . . grew very fast with
abundant breccia material from collapsing and draining pillows, in
particular in the summit region."
On 1 April, another dive along the outer flanks of Vailulu'u found that
during the up-slope transit, observers saw a few additional areas of active
venting and many sites where there had been venting in the past. Large and
perfectly formed pillow lavas were present in most sites, with a few areas
being dominated by broken talus fragments and some having completely black
glassy pillows with no oxidation, apparent evidence for relatively recent
formation. The topography was extremely rough, the slope being punctuated
with numerous fissure systems and edifices of pillow lava.
A primary plan for the ALIA expedition was to study the water in and around
the seamount for several days using a CTD probe. To sample the inside of
the volcano for a full tidal cycle, the scientists varied the depth of the
CTD between 40 and 930 m (almost to the crater floor), collecting various
data, including visibility. At Vailulu'u, the particulates given off by
hydrothermal venting are flushed out of its caldera during each tidal cycle
into the surrounding water. In 2005, a dense layer of particulates was
found in the water within the crater, but the water was clear outside the
crater rim. This contrasts with observations seen from the cruise in 2000,
when there was a dense ring of particulates around the whole volcano. It
appears that in 2005 the particulates were rising above the crater and then
later sinking, instead of forming the widespread ring observed in 2000.
In addition, the expedition crew conducted dredging of the new summit of
Nafanua. Staudigel and Hart noted that the rocks from the first dredge haul
were quite newly formed, containing pristine olivine-phyric volcanic rocks.
Abundant large vesicles in the rocks from Nafanua suggest a volatile-rich
magma capable of submarine lava fountaining and explosive outgassing in
shallower water. Dredging from a second site, outside of Vailulu'u,
recovered rocks that were both much older and far less fragile.
Background. A massive volcanic seamount, not discovered until 1975, rises
4,200 m from the sea floor to a depth of 590 m about one-third of the way
between Ta'u and Rose islands at the eastern end of the American Samoas.
The basaltic seamount, named Vailulu'u, is considered to mark the current
location of the Samoan hotspot. The summit of Vailulu'u contains a
2-km-wide, 400-m-deep oval-shaped caldera. Two principal rift zones extend
east and west from the summit, parallel to the trend of the Samoan hotspot,
and a third less prominent rift extends SE of the summit. The rift zones
and escarpments produced by mass wasting phenomena give the seamount a
star-shaped pattern. On July 10, 1973, explosions from Vailulu'u were
recorded by SOFAR (hydrophone records of underwater acoustic signals). An
earthquake swarm in 1995 may have been related to an eruption from the
seamount. Turbid water above the summit shows evidence of ongoing
hydrothermal plume activity.
References: Hart, S.R., Staudigel, H., Koppers, A.A.P., Blusztajn, J.,
Baker, E.T., Workman, R., Jackson, M., Hauri, E., Kurz, M., Sims, K.,
Fornari, D., Saal, A., and Lyons, S., 2000, Vailulu'u undersea volcano: The
new Samoa: Geochemistry, Geophysics, Geosystems (G3), American Geophysical
Union, v. 1, no. 12, doi: 10.1029/2000GC000108.
Konter, J.G., Staudigel, H., Hart, S.R., and Shearer, P.M., 2004, Seafloor
seismic monitoring of an active submarine volcano: Local seismicity at
Vailulu'u Seamount, Samoa: Geochemistry, Geophysics, Geosystems (G3),
American Geophysical Union, v. 5, no. 6, QO6007, doi: 10.1029/2004GC000702.
Lippsett, L., 2002, Voyage to Vailulu'u: Searching for Underwater
Volcanoes. Woods Hole Oceanographic Institution, Fathom online magazine
(URL: www.fathom.com/feature/122477/).
Staudigel, H., Hart, S.R., Koppers, A., Constable, C., Workman, R., Kurz,
M., and Baker, E.T., 2004, Hydrothermal venting at Vailulu'u Seamount: The
smoking end of the Samoan chain: Geochemistry, Geophysics, Geosystems (G3),
American Geophysical Union, v. 5, no. 2, QO2003, doi: 10.1029/2003GC000626.
Information Contacts: Hubert Staudigel, Institute of Geophysics and
Planetary Physics, Scripps Institution of Oceanography, Univ. of
California, San Diego, La Jolla, CA 92093-0225, USA (Email:
hstaudigel@ucsd.edu; URL:
earthref.org/PACER/team/...audigel.htm;
igpp.ucsd.edu); Stanley R. Hart, Woods Holes Oceanographic
Institute, Geology and Geophysics Dept., Woods Hole, MA 02543, USA (Email:
shart@whoi.edu); ALIA Expedition, Samoan Seamounts, R/V Kilo Moana
(KM0506), supported by the San Diego Supercomputer Center and the Scripps
Institution of Oceanography (URL: earthref.org/ERESE/projects/ALIA/).
Awu
Great Sangihe Island, Indonesia
3.67°N, 125.50°E; summit elev. 1,320 m
All times are local (= UTC + 8 hours)
Awu's eruption on 6 June 2004 and its elevated seismicity in early August
2004 was previously reported (Bulletin v. 29, no. 10). This report covers
the last half of August 2004, which had not been reported on previously.
Since the 6 June eruption, observation of the summit failed to reveal any
significant changes (table 1). The hazard status of Awu during this August
report remained at Level 2, having been elevated to 4 (the highest on a
scale of 1 to 4) at the time of the 6 June eruption and then lowered on 14
June.
Table 1. Seismicity at Awu during August 2004 as reported by DVGHM.
Date Volcanic A Volcanic B Tectonic
08 Aug-15 Aug 2004 -- -- 75
16 Aug-22 Aug 2004 2 1 81
23 Aug-29 Aug 2004 2 -- 102
Background. The massive Gunung Awu stratovolcano occupies the northern end
of Great Sangihe Island, the largest of the Sangihe arc. Deep valleys that
form passageways for lahars dissect the flanks of the 1,320-m-high volcano,
which was constructed within a 4.5-km-wide caldera. Awu is one of
Indonesia's deadliest volcanoes; powerful explosive eruptions in 1711,
1812, 1856, 1892, and 1966 produced devastating pyroclastic flows and
lahars that caused more than 8,000 fatalities. Awu contains a summit crater
lake that was 1 km wide and 172 m deep in 1922, but was largely ejected
during the 1966 eruption.
Information Contacts: Dali Ahmad, Directorate of Volcanology and Geological
Hazard Mitigation (DVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia
(Email: dali@vsi.dpe.go.id; URL: www.vsi.dpe.go.id).
Karthala
Grand Comore Island, Comoros
11.75°S, 43.38°W; summit elev. 2,361 m
All times are local (= UTC + 3 hours)
After a long period of quiescence following the 1991 phreatic eruption,
Karthala's seismicity rebounded starting in July 2000 (Bulletin v. 25,
no.10). In October 2000, more than 20 seismic events per day were recorded.
The local observatory and a key source for this report is the Karthala
Volcano Observatory (KVO; Netter and Cheminee, 1997). They maintain close
ties with the Centre National de Documentation et de Recherche Scientifique
des Comores (CNDRS), Reunion Island University, the Institut de Physique du
Globe de Paris, Piton de la Fournaise Volcanological Observatory, and
various universities in France.
Activity during October 2000-March 2004. Between October 2000 and January
2003, relatively low seismicity was detected beneath Karthala's summit. The
seismicity slowly increased. During January instruments recorded 51
earthquakes on the 5th, 58 on the 10th, and 50 on the 11th. During the
month of April 2003 instruments registered 732 (i.e. averaging ~24 each day).
Seismic instruments detected several short earthquake swarms, each
comprised of ~150 earthquakes. These swarms took place on 25 March and in
April 2003, and each lasted several hours. Moreover, seismologists
witnessed another swarm consisting of 183 events on 15 May. Except for that
latter swarm, Karthala's seismicity was relatively quiet for 35 days after
the 25 April swarm. A photo of the Chahale crater from the year 2003, well
before the April 2005 eruption, appears in figure 10. (For a map of
Karthala's summit, see Bulletin v. 16, no. 8.)
Figure 10. Karthala's ~ 300-m-diameter Chahale crater as seen on 15 August
2003, more than a year prior to the April 2005 eruption. The photo was shot
by the automatic camera located at the summit, looking from the NNE towards
the SSW. The 2005 eruption dramatically changed this scene, replacing the
green lake seen here with a lava lake, and blanketing considerable areas
with tephra. Courtesy of Nicolas Villenueve.
During the time interval from early June 2003 to January 2004 instruments
registered three periods with elevated seismicity. The first interval
spanned 121 days from June until the end of September 2003 and included
6,315 earthquakes. Within that interval there was a major crisis on 6th
September, comprised of 345 events, some being felt by local residents
(Bulletin v. 28, no. 8).
The second interval began on 11 October 2003, reaching its peak on 4
January 2004 (253 events) and stopped on 31 January 2004. During this
interval of 113 days, instruments registered 4,431 earthquakes. The third
interval, during the time period of 3 February to 5 March 2004, contained
fewer earthquakes. Instruments recorded 832 events in 31 days with a
maximum of 143 events per day. After the third interval, KVO recorded only
low seismicity until early 2005, when daily events rose to 50-60.
Eruption during April 2005. A seismic crisis began at 0812 on 16 April.
Although instruments initially received only short-period events, starting
at 0914 they also registered many long-period ones. From 1055 on 16 April a
continuous signal was recorded, which was interpreted as tremor marking the
beginning of the eruption. At around 1400 that day inhabitants heard a
rumbling coming from the volcano. A few minutes later they observed an ash
column above the summit. The first ash-fall deposits began to form around
1600, developing on the island's eastern side. According to the firsts
reports, ash deposition increased and continued through the night
accompanied by a strong smell of sulfur.
On the morning of 17 April ash falls continued on the eastern part of the
island and were heavy enough to require inhabitants to use umbrellas to get
about. At midday, Jean-Marc Heintz, a pilot for Comores Aviation, flew over
the west flank and observed a large plume in the direction of the Chahale
crater. He also clearly observed airborne molten ejecta.
Around 1300, observers saw a very dark plume, spreading into a mushroom
shape and accompanied by lightning flashes. Some inhabitants panicked and
fled the island's eastern villages. In the afternoon, residents heard
rumbling. During the evening, significant rainfall generated small
mudflows, and the rumbling became stronger.
At that time, authorities evacuated some eastern villages (according to
Agence France Presse (AFP) this affected ~10,000 people). Ash there started
to fall on the island's western and northern parts, notably, on the
country's capital city of Moroni (~10 km NW of the summit) and on the
Hahaya airport (~20 km N of Moroni, ~25 km NW of the summit). Figure 11
shows a photo with the base of a vigorous plume over the E flanks on the
afternoon of 17 April.
Figure 11. A phreatic eruption as seen from Karthala's eastern slopes on
the afternoon of 17 April 2005. The vent lies below the white-colored zone
in the center-right portion of the photo. With enlargement, many parts of
the image record the descent of large pieces of ejecta. Photo credit to
school teacher Daniel Hoffschir.
KVO authorities sometimes witnessed a red color at the plume's base,
interpreted as a sign of an ongoing magmatic eruption. At 2105 the KVO
seismic network recorded a drastic decrease in the amplitude of the tremor.
During the night of 17-18 April, wide variations of the tremor amplitude
were recorded with a maximum at 0140 on 18 April and a minimum at 0430 on
18 April. Thereafter, the tremor amplitude did not increase. During the
night of 17-18 April the plume and falling ash disappeared.
On an overflight of the Chahale crater at 0830 on 18 April, KVO personnel
observed major modifications at the summit (figures 12-14). A lava lake
(figure 12) had replaced the water-bearing lake (figure 10) that had
occupied the crater since 1991.
Figure 12. On 18 April 2005 the Karthala eruption generated a lava
lake in the Chahale crater. In this photo, taken the morning of 18 April,
considerable portions of the lava lake's surface still remained molten and
incandescent.. The lake's surface only remained molten for a few hours.
This aerial photo was taken looking from the N. Courtesy of Hamid Soule.
Figure 13. A 19 April 2005 aerial photograph of Karthala taken from the SE
centered on Chahale crater. The lava lake's surface had chilled and it
emitted white vapor. Much of the summit area displays the recently
deposited smooth-surfaced tephra blanket. Courtesy of Nicolas Villenueve.
Figure 14. Tephra deposits left by Karthala's mid-April 2005 eruption
altered the landscape and destroyed vegetation. This picture was taken at
the entrance to the first caldera on the western trail, viewed looking to
the S. Courtesy of Nicolas Villenueve.
On 19 April a new overflight revealed the crater floor containing the lava
lake, with its chilled surface emitting steam (figure 13). Lava remained
confined to Chahale crater. Around the caldera area, and particularly on
its N, observers saw conspicuous tephra deposits; most of the vegetation
had been destroyed (figure 14).
On 20 April a field excursion found that ash deposits varied in thickness
from a few millimeters on the coast to ~1.5 m at the summit. Near the
summit the observers recognized some post-eruptive evaporation and
geothermal processes. Specifically, although the lava lake's surface had
frozen, there remained sufficient heat under the surface that groundwater
migrating towards to the crater's floor evaporated into steam. During
another field survey on 8 May, observers noted the renewed presence of lake
water inside the crater.
Background. The southernmost and largest of the two shield volcanoes
forming Grand Comore Island (also known as Ngazidja Island), Karthala
contains a 3 x 4 km summit caldera generated by repeated collapse.
Elongated rift zones extend to the NNW and SE from the summit of the
Hawaiian-style basaltic shield, which has an asymmetrical profile that is
steeper to the south. The lower SE rift zone forms the Massif du Badjini, a
peninsula at the SE tip of the island. Historical eruptions have modified
the morphology of the compound, irregular summit caldera. More than twenty
eruptions have been recorded since the 19th century from both summit and
flank vents. Many lava flows have reached the sea on both sides of the
island, including during many 19th-century eruptions from the summit
caldera and vents on the northern and southern flanks. An 1860 lava flow
from the summit caldera traveled ~13 km to the NW, reaching the western
coast north of the capital city of Moroni.
Reference: Netter, C., and Cheminee, J. (eds.), 1997, Directory of Volcano
Observatories, 1996-1997: World Organization of Volcano Observatories
(WOVO), WOVO/IAVCEI/UNESCO, Paris, 268 p.
Information Contacts: Nicolas Villeneuve (CREGUR, Centre de Recherches et
d'Etudes en Geographie de l'Universite de la Reunion), Hamidou Nassor, and
Patrick Bachelery (LSTUR, Laboratoire des Sciences de la Terre), Universite
de La Reunion BP 7151, 15 Avenue, Rene Cassin, 97715 Saint-Denis, Reunion
Island (Email: Nicolas.Villeneuve@univ-reunion.fr;
Patrick.Bachelery@univ-reunion.fr); Francois Sauvestre and Hamid Soule,
CNDRS, BP 169, Moroni, Republique Federale Islamique des Comores (Email:
obs_karthala@ifrance.com; URL:
volcano.ipgp.jussieu.fr:8080/kar...ml).
Ol Doinyo Lengai
Tanzania, eastern Africa
2.751°S, 35.902°E; summit elev. 2,960 m
Al times are local (= GMT + 3 hours)
Although lava venting at Ol Doinyo Lengai continued intermittently after
February 2004 (Bulletin v. 29, no. 2), no significant changes were detected
until July 2004, a time when vigorous venting emitted substantial amounts
of the low-viscosity carbonatitic lava typical at this volcano ('flash
floods' of lava). This summary report covers the time interval from
February 2004 through early February 2005 based on observations made by
Frederick Belton, Celia Nyamweru, Bernhard Donth, and Christoph Weber.
Websites devoted to Ol Doinyo Lengai, including photographs, information on
the evolution, recent history, and current status of the volcano are
maintained by Belton, Nyamweru, and Weber.
A map, thermal data, and some new elevation estimates. In February 2005
Weber and others collected location data with a global positioning system
(GPS) receiver. Weber used this to create a sketch map of the active crater
(figure 15).
Figure 15. Sketch map of crater features at Ol Doinyo Lengai surveyed with
a global positioning system (GPS) during 3-7 February 2005. During the
course of the report interval, new vents developed at T49G and T58C (amid
the N-central group of hornitos; T49G sits ~ 10 m E of T49B). These new
vents produced comparatively vigorous eruptions. Courtesy of Chris Weber
(Volcano Expeditions International, VEI).
In July 2004 Belton completed the third of a series of distance
measurements across crater outflow areas at the crater rim (table 2). Due
to the unusually strong eruption on 15 July 2004 (figure 16), deposits
comprising the E overflow widened by 3 or 4 m (growing from 44 to 47 m,
figure 15). Later, in January 2005, observers noticed a fourth area of
overflows had become established on the N crater rim, with lavas pouring
over the rim at two adjacent points there (figure 15).
Table 2. For Ol Doinyo Lengai, the width of the three extant lava outflows
at the points where they spilled from the active crater ('overflows,'
figure 15), as measured during 2 August 2003-29 July 2004. Two additional
small overflows formed later, by January 2005, on the N crater rim. The 3-m
E-overflow increase occurred during the eruption of T58C on 15 July 2004.
Courtesy of Frederick Belton.
Crater rim Date of Width (m)
overflow area measurement
NW overflow 02 Aug 2003 135
NW overflow 29 Jun 2004 135
NW overflow 29 Jul 2004 135
E overflow 02 Aug 2003 44
E overflow 29 Jun 2004 44
E overflow 29 Jul 2004 47
W overflow 02 Aug 2003 17
W overflow 29 Jun 2004 18
W overflow 29 Jul 2004 18
Figure 16. A time exposure photograph of Ol Doinyo Lengai taken just after
sunset on 15 July 2004. At that time the newly formed vent T58C ("Charging
Rhino") issued copious lava. This photo was taken looking approximately NW
from the SE part of the crater rim. Courtesy of Frederick Belton.
During 3-7 February 2005 Weber and others completed a series of lava and
fumarole temperature measurements that appear as tables 3 and 4. The tables
indicate the hottest lava and fumarole temperatures at cracks were 588°C
(at T49C, February 2004) and 150°C (at T49G, June 2004), respectively. The
hornitos T49C and T49G both lie near T49B, a hornito delineated on figure 15.
Table 3. Repeated maximum lava temperatures measured at Ol Doinyo Lengai
during 28 August 1999 to 3 February 2005. The measurements were made
employing a digital thermometer (TM 914C with a stab feeler of standard K
type). The instrument was used in the 0-1200°C mode, and at least four
replicate measurements were made at any one spot. Calibration was by the
delta-T method; uncertainties were +- 6°C in the 0-750°C range. Courtesy of
C. Weber.
Date Location
Temperature (°C)
28 Aug 1999 T40 lava
lake 529
01 Sep 1999 Pahoehoe flow in a tube near
T40 519
01 Sep 1999 Aa flow still in motion at flat terrains (60 cm
thick) 516
03 Oct 2000 Pahoehoe flow in a tube near
T49B 507
03 Oct 2000 Aa flow still in slow motion at flat terrain (25 cm
thick) 496
11 Feb 2004 Pahoehoe flow in a tube near
T49G 588
12 Feb 2004 Pahoehoe flow in a tube near
T49B 579
13 Feb 2004 Aa flow not in motion anymore at flat terrain (15 cm
thick) 490
26 Jun 2004 Pahoehoe flow in slow motion (10 cm thick) flat
terrain 560
03 Feb 2005 Pahoehoe flow (15 cm thick) in motion traveling within
a levee. 561
03 Feb 2005 Aa flow not in motion anymore at flat terrain (15 cm
thick) 520
Table 4. Maximum fumarole temperatures measured at cracks in Ol Doinyo
Lengai's crater floor over a series of visits during 28 August 1999 to 4
February 2005. Collected using the digital thermometer with procedures and
parameters noted with the previous table. For locations, see map (figure
15). Courtesy of C. Weber.
Date Location Temperature (°C)
28 Aug 1999 F1 70
28 Aug 1999 Near T49 82
03 Oct 2000 Near T49C 75
03 Oct 2000 F1 69
20 Oct 2002 The hottest cracks in the crater floor 124
20 Oct 2002 F1 78
30 Jun 2003 F1 86
30 Jun 2003 Near T49C 76
12 Feb 2004 F1 88
26 Jun 2004 F1 78
26 Jun 2004 Near T49C 150
04 Feb 2005 F1 84
Weber's team GPS measurements suggested a summit elevation of 2,960 +- 5 m.
This is consistent with GPS measurements taken in October 2000, by a
scientific group led by Joerg Keller, of 2,950-2,960 m (Bulletin v. 25, no.
12). In addition, the tallest hornito in the N-central crater rises to
nearly this elevation (see discussion of T49/T56B, below).
During observations in February 2004, Weber measured the tallest hornito at
the T49 location (part of T56B) in the center area of the active crater.
GPS readings on top of T56B yielded an elevation of 2,886 m. This is only 4
m below the elevation of the summit and within the stated, +- 5m
uncertainty of that measurement. The top of T49 is also ~33 m above the
adjacent crater floor to the N. In addition, when he measured on 3-7
February, Weber found hornito T58C (a then recent feature) had grown to
reach an elevation of ~2,870 m.
Observations during February 2004 to February 2005. During February 2004
visits, T56B did not erupt, but instead a new vent erupted at the T49
location (~10 m E of T49B, see also Bulletin, v. 29, no. 2). This new vent
was called T49G (figure 15).
A group from Volcano Expeditions International (VEI) spent 24-30 June 2004
on Lengai and found much of the scene at the vents in the crater similar to
that noted in February 2004. They noted that half of the upper 10 m of
hornito T56B had collapsed on its E side, and an active lava lake had
formed inside this hornito with lava escaping several times through the
collapsed opening to its E and flowing out ~200 m. The lava was rich in gas
with a temperature of 560°C. The hornito T58B was also active and spattered
lava many times during these days of observation. Some lava flows from T58B
reached about 150 m to the S.
During 2-3 July 2004, Belton observed T58B erupt repeatedly, emitting lava
and strombolian displays. The escaping lava flowed S, passing near the base
of hornito T47. On 4 July, Belton saw some of the most intense activity of
the month. A sequence of lavas erupted on that day and over the next few
days. However, events in mid-July and later were also unusually vigorous.
The 4 July 2004 activity included strong strombolian eruptions at T58B and
several collapses of its vent area, which released large cascades of lava
onto the crater floor. Simultaneously, a tube-fed eruption of pahoehoe lava
from the new vent T49G flowed across the NW crater rim to spill down that
flank. Early on 5 July numerous eruptions of T58B sent lava flowing toward
T47 at an estimated velocity of 10 m/sec. On 6 July, lava flowed out of the
lake in T56B and onto the crater floor moving E and entering a cave in T45
for a short distance.
After very low activity during 7-10 July 2004, renewed flows and spatter
came out on 11 July from T58B, and frequent but short (usually ~2 minute)
episodes of loud degassing and spattering issued from the lava lake in
T56B. At night, this vent emitted incandescent gas. This pattern continued
until the morning of 14 July, when eruptions at T58B became more explosive
and it expelled small ash clouds. On the morning of 15 July a collapse in
the vent area of T58B released large rapid lava flows to the E. The
episodes of degassing and spattering from T56B increased in frequency until
1500 on 15 July, when a small hole formed in the crater floor just E of T58B.
Called T58C, the hole became a newly opened vent. It began emitting visible
gas puffs mixed with spatter. At this time the degassing episodes from T56B
ceased. T58C then began strong degassing and squirted up intermittent lava
fountains. The fountains soon fed a large lava stream moving toward the S
crater wall.
By 1600 on 15 July 2004 a paroxysm at T58C was in progress, with lava
forming 10- to 12-m-tall fountains and 'flash floods' that completely
inundated the central-eastern crater floor (in the area between T56B, T58B,
T37, T37B, T45, and T57). T58C also ejected strong jets of ash and gas.
Turbulent rivers of lava flowing at more than 10 m/sec swept toward the
crater's S wall and its E overflow and completely surrounded T37B and T45.
Flow rate from the vent was estimated to peak at 10 m^3/s.
The momentum of the rapidly outflowing lava carried it nearly 3 m up the W
(upstream) side of T45 and obliterated the large cave within that cone. The
associated surge of lava poured over the E crater rim and down the flank.
It flooded over a 3 m wide swath of vegetation. This triggered a huge cloud
of steam and smoke that resembled a small pyroclastic flow. The smoke cloud
was accompanied by a loud sizzling sound. A brush fire burned along the
crater rim overflow as additional floods of lava arrived. These
larger-than-normal flows lasted for little more than 30 sec and were
separated by periods of repose of 5 to 6 min. After sunset, incandescent
gas flared from the vent during the repose periods. Weak strombolian
activity was seen in T56B.
Early on 16 July 2004 the newly formed T58C was a circular pit ~2 m in
diameter with lava sloshing violently at a depth of ~2 m. Two small
sub-vents on the N and S edges of the pit interconnected with the main
vent. Activity continued sporadically at T58B and T56B with strombolian
activity and lava flows. On 21 July there was an exceptionally strong
eruption of T58B with loud explosions, jetting of ash-poor clouds, and
spatter thrown to above-average heights. Explosions blasted a new vent in
the upper E side of T58B. At least four oval bombs 9-12 cm in length flew
through the air, along with a great deal of lapilli and ash. Later
examination of the bomb's interiors revealed that they all had an outer
zone ~1.5- to 2-cm thick and a distinctive inner core.
On 23 July 2004, a sloping ~4 m^2 oval section of the crater floor
immediately SW of the new spatter cone T58C began to steam and vibrate.
Tremor increased and ground movement was visible, manifested as a small
section of crater floor rapidly pushed outward and then inward several
centimeters, like a membrane vibrating in time to the degassing sounds of
lava in T58C just behind it. Abruptly this portion of the crater floor
broke outward, and a flood of lava ensued. T58C was observed to grow in
height through the time when Belton left the crater on 29 July 2004.
Observations during January and February 2005. Donth reported that during
his visit on 10 January 2005, hornito T49B erupted to form many effusive
lava flows. For the first time, lava escaped over the northern edge of the
crater (see figure 15).
During Weber's crater visit, 3-7 February 2005, the hornito T49B actively
emitted lava flows that traveled to the N. Pahoehoe lava flows in motion
within small levees on flat terrain were measured from 520°C up to a
maximum of 561°C (table 3). The fumaroles at F1 had a maximum temperature
of 84°C, and at hornito T46, a maximum of 91°C (table 4). No change in
distance was measured across the CR1, CR2, and CR3 cracks cutting the upper
crater walls. Adding to visitor safety concerns, which include altitude
sickness, burns, falls, and impact from ejecta, Weber's team saw a spitting
cobra close to the summit. An overflight by plane on 14 February showed no
subsequent change, but did give an excellent view of the crater and its
central hornitos (figure 16).
A flight on 14 February failed to reveal subsequent changes. But the effort
provided an excellent view of the crater and its central hornitos (figure 17).
Figure 17. An aerial photograph taken looking towards the WSW at the summit
crater of Ol Doinyo Lengai on 14 February 2005. The summit, which lies in
the upper left corner has a revised elevation based on GPS (see text). In
addition, GPS elevations and uncertainties suggest that in 2005 the summit
was only marginally higher than the top of the tallest hornito (T56B).
Copyrighted photo provided courtesy of T. Schulmeister and C. Weber.
Background. The symmetrical Ol Doinyo Lengai stratovolcano is the only
volcano known to have erupted carbonatite tephras and lavas in historical
time. The prominent volcano, known to the Maasai as "The Mountain of God,"
rises abruptly above the broad plain S. of Lake Natron in the Gregory Rift
Valley. The cone-building stage of the volcano ended about 15,000 years ago
and was followed by periodic ejection of natrocarbonatitic and nephelinite
tephra during the Holocene. Historical eruptions have consisted of smaller
tephra eruptions and emission of numerous natrocarbonatitic lava flows on
the floor of the summit crater and occasionally down the upper flanks. The
depth and morphology of the northern crater have changed dramatically
during the course of historical eruptions, ranging from steep crater walls
about 200 m deep in the mid-20th century to shallow platforms mostly
filling the crater. Long-term lava effusion in the summit crater beginning
in 1983 had by the turn of the century mostly filled the northern crater;
by late 1998 lava had begun overflowing the crater rim.
Information Contacts: Christoph Weber, Volcano Expeditions International,
Muehlweg 11, 74199 Untergruppenbach, Germany (URL: www.v-e-i.de,
Email: mail@v-e-i.de); Celia Nyamweru, Department of Anthropology, St.
Lawrence University, Canton, NY 13617, USA (URL:
it.stlawu.edu/~cnya/; Email: cnyamweru@stlawu.edu); Frederick
Belton, Developmental Studies Department, PO Box 16, Middle Tennessee State
University, Murfreesboro, TN 37132, USA (URL:
www.oldoinyolengai.org, Email: oldoinyolengai@ hotmail.com); Bernard
Donth (Email: b.donth@ saarschmiede.com).
__________________________________________________________
Global Volcanism Program, NHB E-421 Tel: (202) 633-1800
Smithsonian Institution Fax: (202) 357-2476
Washington, DC 20560-0119 Email: gvp@si.edu
Internet: www.volcano.si.edu/
-
Re: GVN Bulletin
Fri, July 15, 2005 - 2:13 PM***************************************************
Bulletin of the Global Volcanism Network, May 2005
***************************************************
From: Ed Venzke <venzke@volcano.si.edu>
Bulletin of the Global Volcanism Network
Volume 30, Number 5, May 2005
<www.volcano.si.edu/reports/...bgvn.pdf>
Ambrym (Vanuatu) Steady emissions of SO2 create health problems, destroy
crops, and contaminate water
Manam (Papua New Guinea) Aircraft encounters airborne gas from 27 January
2005 eruption; infrasonics
Langila (Papua New Guinea) Ash emissions and lava flow during April-June 2005
Egon (Indonesia) Three eruptions in February 2005 eject ash and gas
Karangatang (Indonesia) Ongoing seismicity during January-February 2005;
lava avalanche in January
Barren Island (India) Lava flow and ash discharges seen by Coast Guard
personnel on 28 May 2005
Long Valley (USA) Minor seismicity throughout 2004
Reventador (Ecuador) Lava flow reaches 4 km from summit, approaching road
and petroleum pipeline
Lascar (Chile) Further analysis of 4 May 2005 event indicates a
phreato-Vulcanian eruption
Rotorua (New Zealand) Hydrothermal eruption of 19 April 2005-one of the
area's largest since 1948
White Island (New Zealand) Seismic and hydrothermal activity remain low
through June 2005
Editors: Rick Wunderman, Catherine Galley, Edward Venzke, and Gari Mayberry
Volunteer Staff: Robert Andrews, William Henoch, Clement Pryor, Jacquelyn
Gluck, and Stephen Bentley
Ambrym
Vanuatu, SW Pacific
16.25°S, 168.12°E; summit elev. 1,334 m
All times are local (= UTC + 11 hours)
Jenifer Piatt, a meteorologist with the Air Force Weather Agency in the
Satellite Applications Branch, notified Bulletin staff on 17 June 2005 that
haze had appeared near Ambrym on MODIS imagery over the past few days. Over
the past several months, this volcano had been emitting SO2 and sometimes
light ash. She informed us of several recent news articles that addressed
this event and provided several satellite images (figure 1).
Figure 1. Images for 0250 UTC 15 June 2005 (top), and 0240 UTC 17 June 2005
(bottom) disclosing the area around Vanuatu including Ambryn. The images
came from NASA's AQUA MODIS satellite with a resolution of 500 m. SO2
plumes from Ambrym are labeled. NASA image courtesy of USAF Weather Agency.
Tony Ligo wrote on 1 June 2005 in the Port Villa Presse that acid rain
continued to fall in W Ambrym Island in Vanuatu, even after ash from the
volcano had stopped falling. This prompted the provincial secretary general
to discuss the need for new water sources. The Vanuatu government, through
the department of Rural Water Supply, agreed to provide a drilling rig to
the Malampa provincial government to drill on W Ambrym as soon as possible.
The government also recognized the value of scientific and technical data;
in order to effectively respond to such environmental problems the
government needs to get more young people studying in this area. The
article noted that Vanuatu only has one volcanologist, Charley Douglas,
with enough background to give accurate data on current activity.
Aid and food have been sent to affected areas on the western coast of the
island, and a contingency evacuation plan is required for resettling people
should this be necessary in the future. Health issues have been raised
regarding hygiene, respiratory problems, asthma, and malnutrition over the
past couple of months. Of great concern are health problems particular to
children, including exposure to excess fluoride and the consequent risk of
bone disease.
The National Aeronautics and Space Administration (NASA) Earth Observatory
web site reported that Ambrym volcano was the strongest point source of SO2
on the planet for the first months of 2005; it had been steadily emitting
SO2 for at least 6 months, and satellite images produced using data
collected by the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite
during the first 10 days of March 2005 show high concentrations of SO2
drifting NW.
The web site article noted that "Ambrym is not erupting in the traditional
sense with thick ash plumes and explosive bursts of lava, rather it is
leaking SO2 gas from active lava lakes in what scientists call 'passive"or
"non-eruptive" emissions. Despite these gentle names, the volcano still
threatens the local population. SO2 has a strong smell and can irritate the
eyes and nose and make breathing difficult. Higher in the atmosphere, SO2
combines with water to create rain laced with sulfuric acid. On Ambrym,
acid rain has destroyed staple crops and contaminated the water supply,
leaving communities in need of food aid." In the past, satellites have been
able to monitor SO2 emissions only from large eruptions or the most
powerful passive degassing. All other SO2 emissions remain at low altitudes
and have low SO2 concentrations that were hard to see from space.
On 15 July 2004, NASA launched its Aura satellite carrying the OMI, which
is part of a collaboration between the Netherlands' Agency for Aerospace
Programs, the Finnish Meteorological Institute, and NASA. With greater
spatial resolution (the ability to "zoom-in" to see greater detail) and
higher sensitivity to SO2 than any previous space-borne sensor, OMI allows
scientists to study passive volcanic degassing on a daily basis for the
first time.
The image in figure 2 is an example of the instrument's preliminary,
uncalibrated, and unvalidated data. This new view of passive volcanic
emissions could lead to significant advances in understanding both volcanic
eruptions and the impact of SO2 on climate. Changes in passive emissions
can be a precursor to explosive eruptions, and thus provide a warning
signal that activity may be changing.
Figure 2. A zone of elevated atmospheric SO2 from Ambrym during
the interval 1-10 March 2005. The units on the scale bar reflect SO2 in
terms of Dobson Units (DU). (A Dobson Unit represents the physical
thickness of the SO2 gas if a 1 cm2 column of the atmosphere were brought
to 0EC and 1 atmosphere pressure. A value of 300 Dobson Units equals three
millimeters.) To process the OMI spectrometer data, two different pairs of
measured UV wavelengths are averaged. The mean of pairs 1 and 2 is
written as "P1-P2 mean" on the scale bar. Courtesy of Simon Carn.
Background. Ambrym, a large basaltic volcano with a 12-km-wide caldera, is
one of the most active volcanoes of the New Hebrides arc. A thick, almost
exclusively pyroclastic sequence, initially dacitic, then basaltic,
overlies lava flows of a pre-caldera shield volcano. The caldera was formed
during a major Plinian eruption with dacitic pyroclastic flows about 1,900
years ago. Post-caldera eruptions, primarily from Marum and Benbow cones,
have partially filled the caldera floor and produced lava flows that ponded
on the caldera floor or overflowed through gaps in the caldera rim.
Post-caldera eruptions have also formed a series of scoria cones and maars
along a fissure system oriented ENE-WSW. Eruptions have apparently occurred
almost yearly during historical time from cones within the caldera or from
flank vents. However, from 1850 to 1950, reporting was mostly limited to
extra-caldera eruptions that would have affected local populations.
Information Contacts: Jenifer E. Piatt, HQ Air Force Weather Agency
Satellite Applications Branch (URL: Jenifer.Piatt@afwa.af.mil); Simon Carn,
TOMS Volcanic Emissions Group, University of Maryland, 1000 Hilltop Circle,
Baltimore, MD 21250, USA (Email: scarn@umbc.edu; URL:
skye.gsfc.nasa.gov/); NASA Earth Observatory Natural Hazards web
page (earthobservatory.nasa.gov/Natur...rds/).
Manam
Papua New Guinea
4.10°S, 145.06°E; summit elev. 1,807 m
All times are local (= UTC + 10 hours)
Manam erupted several times during October to December 2004 and January
2005. A strong eruption on 24 October 2004, preceded by a buildup in
seismicity and a felt earthquake, was described in Bulletin v. 29, no. 10.
This eruption generated pyroclastic flows, and its plume was imaged from
space. The eruption sent ash and condensed water in the form of ice to a
maximum height of ~15 km altitude. On 10-11 November 2004, a Strombolian
eruption occurred; the ash column was estimated to have risen ~5-6 km above
the crater. On 23-24 November 2004 Manam's main crater ejected glowing lava
and discharged an ash cloud that rose ~10 km high. A lava flow was also
reported to be heading for two villages on the island. Details and reports
of eruptions in November and December 2004 were included in Bulletin v. 29,
no.11.
The eruption at Manam on the evening of 27 January 2005 (Bulletin v. 30,
no. 2) was more severe than the previous ones during the current eruptive
period. During 27-28 January 2005 there were 14 people injured and one
person killed at Warisi village. The reports of the Rabaul Volcano
Observatory (RVO) and the Darwin VAAC, and an analysis of the Manam
eruption clouds by Andrew Tupper of the Darwin VAAC, were summarized in
Bulletin v. 30, no. 2. In late January, five commercial flights were
cancelled from Rabaul, East New Britain, delaying about 100 passengers.
Documented occurrence of olfactory fatigue. A report received from Andrew
Tupper discussed an encounter of an aircraft with an airborne gas plume
that took place about 2300 UTC on 29 January (0800 on the 30th, East Timor
time) reported to him by a pilot. The encounter took place at a
considerable distance from Manam, and a map is helpful to visualize the
region's geography (figure 3). The incident involved entry into a visibly
anomalous, hazy-blue cloud that turned out to contain sulfurous odor
(figure 4). Although Tupper and the pilot discussed other possibilities for
the cloud's origin, Tupper came to the conclusion that the cloud was
volcanic fog (vog) erupted from Manam.
Figure 3. The airport at Dili, East Timor (Indonesia), located about 2,200
km WSW of Manam.
Key portions of the pilot's message conveyed to us by Tupper follow.
"On descent into Dili, approaching 10,000 feet at 12 nautical miles [~3 km
altitude and ~22 km from the airport] aircraft control levers were pulled
back to flight idle just prior to entering a thin layer of smooth stratus
cloud [figure 4].
Figure 4. The hazy blue cloud that produced a sulfur smell in the cockpit
of the plane approaching Dili. The photo was taken by the air crew (names
not given).
"Shortly after passing into the cloud, a strange smell was soon noticed in
the cockpit; once the accusations of responsibility had passed, it quickly
became apparent that the smell was not the result of a bodily function. The
smell became very strong, with high sulfur content. As a precaution the
Captain directed the First Officer to don his oxygen mask. The smell
persisted but began to weaken on descent, and landing was accomplished
without incident. After landing, First Officer removed the oxygen mask and
noted the smell had remained. The captain had by this time become
desensitized to the smell. Upon shutdown, unloading was halted, until such
time as the cargo hold could be examined for a source of the smell. No
smell remained."
Tupper and the pilot discussed possible sources for the smell. The cloud
displayed a distinct blue haze (Tupper commented that "it's difficult to
tell from the attached photo whether the blue is all that
out-of-the-ordinary, but obviously they thought it interesting enough to
take a photo!"). The cloud sat on the hills and appeared to have fog-like
characteristics. The pilot described the odor as sharper and more metallic
than the smell of H2S (a description consistent with SO2, the odor of which
is sometimes described as metallic or akin to a struck-match.
What caused the sulfurous-smelling stratus cloud? The sulfur content may
have come from either nearby volcanoes, none of which have been reported as
active, or from industrial production (possibly Kupang). Due to a serious
dengue outbreak in East Timor, it may have been the result of chemical
mosquito control. Many chemical methods of mosquito control are based on
sulfur products. Malathion is one such product; it contains mercaptan,
which has a strong noxious odor. (Organic compounds with HS bound to carbon
are called mercaptans or thiols and those of low molecular weight have
strong smells. Small doses of mercaptan are often used to give natural gas
a distinctive odor.) One possible way to explain the sulfurous gases was
morning fog moving up the hills of Dili in response to anabatic
(upslope-blowing) winds, which also carried residual insecticide.
Tupper spoke to or emailed the pilot several more times to get the
following other details. The aircraft was an Embraer E120, a 30 seat turbo
prop, with 20-25 people on board. The cabin attendant also noticed the
smell, but no passengers commented. Despite the speculation about chemicals
above, this was the only trip on which the smells had been noticed by the
pilot.
According to Claire Witham, human perception of SO2 odor varies depending
on the individual's sensitivity, but SO2 is generally perceived between
0.3-1.4 ppm and is easily noticeable at 3 ppm. This is generally below the
level where health effects (e.g. respiratory response) might be noted. In
general an exposure limit of 1-5 ppm is the threshold for respiratory
response in healthy individuals upon exercise or deep breathing, whilst at
3-5 ppm the gas is easily noticeable and may cause a fall in lung function
in persons at rest, and increased airway resistance. Asthmatic individuals
may respond at much lower concentrations, and prolonged exposure to low
concentrations carries increased risk for those with pre-existing heart and
lung diseases. A more detailed review of gas hazards and guidelines has
just gone online on the International Volcanic Health Hazard Network.
Significant in this event is that the flight crew thought that the smell
had dissipated. The First Officer, who was wearing an oxygen mask, remained
able to detect that the smell persisted. This indicates that the others in
the crew lost their ability recognize that the sulfurous odors remained, a
well-know effect of sulfurous gases called olfactory fatigue ('bombarded
nerve receptors'), a potentially confusing situation for pilots focused on
escaping from a volcanic plume (Wunderman, 2004).
Tupper conducted dispersion modeling of the 27 January 2005 Manam eruption
(figure 5). The results suggested that the SO2 cloud from the volcano
probably passed over East Timor on the night before the incident and at
higher altitudes. This is supported to a limited extent by the preliminary
ozone and SO2 monitoring results (figure 6), which suggest that the bulk of
the cloud went N, but that part of the cloud traveled over the Banda Sea
and passed over East Timor. The low level winds are highly unlikely to have
carried the SO2 to East Timor, but there was significant storm activity on
the night when the cloud would have passed over. Excluding other
explanations on the grounds that the eruption / encounter timing are
unlikely to be mere coincidence, the most likely explanation for the flight
crew's experience is that some eruption products from Manam were rained out
over East Timor on the night of 29 January 2005. If SO2 had been
incorporated into ice particles, which then rained out, the particles would
have melted and released SO2 at about the level of the encounter, where the
temperature was a bit above freezing. According to this scenario, the plane
then flew through the resultant vog/stratus the next morning.
Figure 5. An ash dispersion model for the eruption cloud associated with
the eruption of Manam on 27 January 2005. The model takes into account wind
at various altitudes and other meteorological data, and predicts the
movement of material injected in the atmosphere. The model used, NOAA
hysplit, adopted the boundary condition that material was above the volcano
between 10 and 24 km altitude starting at 1400 on 27 January. The results
shown predict the dispersal for the interval 1200-1400 on 29 January. The
model indicates that some material from Manam's 27 January eruption
traveled WSW to where the aircraft-gas plume encounter took place. The
model is a product of the NOAA Air Resources Lab with this particular run
provided by Andrew Tupper.
Figure 6. A satellite image of atmospheric SO2 burden from Manam made about
12 hours after the 27-28 January 2005 eruption. The image resulted from the
NASA Ozone Monitoring Instrument (OMI), which flew over the region on
NASA's new Aura satellite. This image was produced from preliminary,
uncalibrated data provided by the OMI. The OMI detected a large cloud of
SO2 drifting W over the island of New Guinea. The gas is measured in Dobson
Units (DU), a reflection of the number of molecules in a square centimeter
of the atmosphere. Darker pixels cover the areas of highest concentration,
while the lowest concentrations are represented by lighter ones (red and
pink, respectively, on the colored electronic version of the Bulletin). If
you were to compress all of the SO2 in a column of the atmosphere into a
flat layer at standard temperature and pressure, one Dobson Unit would be
0.01 mm (millimeters) thick and would contain 0.0285 grams of SO2 per m2.
On January 28, the atmosphere over New Guinea contained up to 50 Dobson
Units (red regions), or 1.425 grams of SO2 per square meter. NASA image and
caption courtesy Simon Carn, Joint Center for Earth Systems Technology.
Infrasound reports. The Comprehensive Nuclear Test Ban Treaty Organisation
(CTBTO) is installing a world-wide network of 60 infrasound stations as
part of the International Monitoring System (IMS) for detection of nuclear
tests. The stations, some of which are already functioning, use
microbarographs (acoustic pressure sensors) to detect very low-frequency
(0.01-10 Hz) sound waves in the atmosphere produced by natural and
anthropogenic events.
The eruption at Manam on 27 January at ~1400 UTC was detected at several
infrasound stations around the Pacific (table 1). In one case a signal was
received at a distance exceeding 10,000 km. The sound of the explosion took
more than ten hours to reach that most distant station, located in
Washington state (USA). The difference in the calculated and measured
signal azimuths is likely caused by high atmosphere winds, and is
reasonable given the great distances that the signal traveled.
Table 1. Arrival times and great circle paths for infrasound signal from
Manam eruption on 27 January 2005 received at CTBTO infrasound stations.
Courtesy of Robert North.
CTBTO Infrasound Station Calculated great
circle Measured Date Arrival
path, station to
volcano signal time
Azimuth Distance azimuth
(°E of N) (km) (°E of N)
I07AU Warramunga, 35 2079 32 27
Jan 2005 16:00 UTC
Central Australia
I22FR New
Caledonia 311 3091 n/a n/a Not obs
I05AU Tasmania, 356 4270 350 27
Jan 2005 18:30 UTC
Australia
I55US Windless Bight, 336 8303 335 27
Jan 2005 22:07 UTC
Antarctica
I53US Fairbanks, 247 9358 252 27
Jan 2005 23:12 UTC
Alaska
I56US Newport, 273 10920 276 28
Jan 2005 00:34 UTC
Washington
Subsequent RVO observations. Although it remained active, Manam calmed
considerably during February-May 2005. During the first two weeks of
February 2005, emissions from Manam continued. On 15 February 2005, the
alert level was reduced from 3 to 2. Mild eruptive activity was observed
from Manam's Southern crater during the third week of February.
Weak-to-moderate ash explosions rose a few hundred meters above the crater
and drifted E and SE, depositing fine ash in areas downwind. Throughout
February, seismicity was at low levels, with small low-frequency
earthquakes occurring and no volcanic tremor. Throughout March,
weak-to-moderate emissions from both the Main and Southern craters
continued to produce occasional ash clouds during most days. On 15 March, a
thin plume from Manam was visible on satellite imagery. On 24 March,
emissions from Main crater rose to ~1 km above the summit. On 28 March, a
moderate explosion produced an ash plume to a height of ~1.2 km above the
summit. Ash plumes drifted N, depositing ash on the island. Seismic
activity fluctuated between low and moderate, with low-frequency
earthquakes recorded.
During April and May 2005, mild eruptive activity continued at the volcano.
Manam remained at alert level 2 from February 2005 through at least late
May. A thin plume extending 55 km NW on 4 May was seen on satellite imagery
by the Darwin VAAC. The ash cloud remained below 3 km altitude.
Background. The 10-km-wide island of Manam, lying 13 km off the northern
coast of mainland Papua New Guinea, is one of the country's most active
volcanoes. Four large radial valleys extend from the unvegetated summit of
the conical 1,807-m-high basaltic-andesitic stratovolcano to its lower
flanks. These "avalanche valleys", regularly spaced 90 degrees apart,
channel lava flows and pyroclastic avalanches that have sometimes reached
the coast. Five small satellitic centers are located near the island's
shoreline on the northern, southern and western sides. Two summit craters
are present; both are active, although most historical eruptions have
originated from the southern crater, concentrating eruptive products during
the past century into the SE avalanche valley. Frequent historical
eruptions have been recorded at Manam since 1616. A major eruption in 1919
produced pyroclastic flows that reached the coast, and in 1957-58
pyroclastic flows descended all four radial valleys. Lava flows reached the
sea in 1946-47 and 1958.
Reference: Wunderman, R., 2004, Sulfurous odors: A signal of entry into an
ash plume-perhaps less reliable for escape, Second International Conference
on Volcanic Ash and Aviation Safety (Alexandria, Virginia, USA), 21-24 June
2004 (Plenary Session 1: Encounters, Damage, and Socioeconomic
Consequences, poster P 1.2, Socioeconomic consequences)
(www.ofcm.gov/ICVAAS/Proc...edings.htm).
Information Contacts: Andrew Tupper, Darwin Volcanic Ash Advisory Centre,
Australian Bureau of Meteorology (URL: www.bom.gov.au/info/vaac);
Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea;
David Innes, Flight Safety Office, Air Niugini, PO Box 7186, Boroko, Port
Moresby, National Capital District, Papua New Guinea (Email:
dinnes@airniugini.com.pg or deejayinnes@yahoo.com, URL:
www.airniugini.com.pg/); International Volcanic Health Hazard
Network (URL: www.ivhhn.org/); Simon Carn, TOMS Volcanic Emissions
Group, Univ. of Maryland, 1000 Hilltop Circle, Baltimore, MD 21250, USA
(Email: scarn@umbc.edu; URL: skye.gsfc.nasa.gov/); Claire Witham,
Meteorology Office, FitzRoy Road, Exeter, EX1 3PB, UK (Email:
claire.witham@metoffice.gov.uk); Robert North, SAIC Monitoring Systems
Division, 1953 Gallows Rd., Vienna, VA 22182, USA
(Email:robert.g.north@saic.com); NOAA Air Resources Lab (ARL), Room 3316,
1315 East-West Highway, Silver Spring, MD 20910, USA (URL:
www.arl.noaa.gov/ready/).
Langila
Papua New Guinea
5.525°S, 148.42°E; summit elev. 1,330 m
All times are local (= UTC + 10 hours)
Langila was last reported on in Bulletin v. 29, no. 6, as part of a MODIS
data summary, although the last prominent event there was on 18 January
2003, when a large explosion produced a thick dark ash column that
penetrated the weather clouds over the summit area (Bulletin v. 28, no. 3).
A plume from Langila was visible on satellite imagery on 17 December 2004
according to the Darwin VAAC. The plume reached an unknown height and
extended NW.
Between 28 April 2005 and 4 May 2005 the Rabaul Volcano Observatory (RVO)
received reports of activity at Langila characterized by forceful emissions
of thick white to gray ash-laden clouds rising ~700-800 m above the summit
crater. Occasional continuous rumbling and explosive noises were heard and
incandescence was visible at night. During early May, incandescent lava
fragments were ejected. Activity increased at about 1300 on 4 May 2005,
when white-to-gray ash emissions changed to dark ash clouds. Explosions
became frequent, with incandescent lava fragments ejected again, and very
bright glow was visible during the night. Around 1200 on 5 May 2005 the
color of the ash emissions changed from dark gray to white-to-gray. A lava
flow was produced but no further detail is available. Based on information
from RVO, the Darwin VAAC reported that ash emissions from Langila rose to
~2.1 km altitude on 3 May. A very small plume and a hot spot were visible
on satellite imagery. Ash clouds from the eruption were blown generally NW
towards Kilenge ~100 km away, where light to moderate ashfall was reported.
According to the Darwin VAAC, low-level ash plumes emitted from Langila
were visible on satellite imagery during 8-13 June 2005. RVO reported to
the Darwin VAAC that moderate eruptive activity was expected to continue.
The International Federation of Red Cross and Red Crescent Societies (IFRC)
reported that eruptive activity occurred at Langila on 2 June with more ash
than normal being emitted from the volcano. Prevailing winds carried most
of the initial ashfall to the sea, but lower-level winds redirected the ash
back onto the island. About 10,000 people live near the volcano, and there
were reports of increased cases of respiratory problems and eye irritation.
During an aerial inspection of the area on 6 June 2005, IFRC determined
that ~3,490 people had been affected by the eruption, mainly in the
villages of Aitavala, Masele, Kilenge, Ongaea, Potne, and Sumel, but also
to a lesser extent in Vem, Galegale, Tauale, and Laut. Ashfall damaged
small food gardens and contaminated some water sources. The provincial
government encouraged voluntary evacuation of affected areas.
During 16-17 June 2005, ash plumes from Langila were visible on satellite
imagery (figure 7). The heights of the plumes were not reported.
Figure 7. On 21 June 2005 the Moderate Resolution Imaging Spectroradiometer
(MODIS), flying on NASA's Aqua satellite, captured this image of Langila,
Ulawun, and Rabaul. At the time MODIS captured this image, Langila showed
the biggest plume of volcanic ash, followed by Ulawun. In all cases, winds
pushed the ash clouds NW over the ocean. NASA image courtesy Jesse Allen,
based on data from the MODIS Rapid Response Team at NASA.
Background. Langila, one of the most active volcanoes of New Britain,
consists of a group of four small overlapping composite basaltic-andesitic
cones on the lower eastern flank of the extinct Talawe volcano. Talawe is
the highest volcano in the Cape Gloucester area of NW New Britain. A
rectangular, 2.5-km-long crater is breached widely to the SE; Langila
volcano was constructed NE of the breached crater of Talawe. An extensive
lava field reaches the coast on the N and NE sides of Langila. Frequent
mild-to-moderate explosive eruptions, sometimes accompanied by lava flows,
have been recorded since the 19th century from three active craters at the
summit of Langila. The youngest and smallest crater (no. 3 crater) was
formed in 1960 and has a diameter of 150 m.
Information Contacts: Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of
Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina,
Northern Territory 0811, Australia (URL: www.bom.gov.au/info/vaac/);
Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea;
International Federation of Red Cross And Red Crescent Societies (IFRC),
Langila Volcano Information Bulletin No. 1 (URL: www.reliefweb.int/).
Egon
Lesser Sunda Islands, Indonesia
8.67°S, 122.45°E; summit elev. 1,703 m
All times are local (= UTC + 8 hours)
Table 2 below tabulates the seismic activity by date of the volcano prior
to and subsequent to its eruption on 6 February 2005, but little was
reported concerning that event. The volcano erupted again on 7 February.
That eruption was accompanied by a strong smell of SO2 or H2S in the
villages of Hebing and Hale and apparently rendered a villager unconscious.
Table 2. A summary of counts for different earthquake types (type B
volcanic, type A volcanic, emission, low frequency, and tectonic), tremor,
amplitude, and Alert Level at Egon volcano. Unreported data indicated by
"--". Courtesy of the Directorate of Volcanology and Geological Hazard
Mitigation (DVGHM) DVGHM.
Date Volcanic Volcanic Emission Low Tectonic
Tremor Alert
B A Frequency
amplitude Level
05 Jan
2005 16 1 7 6 8 2-3
mm 3
06 Jan
2005 48 -- 3 -- 7 1-2
mm 3
Week of 24
Jan 48 1 1 53 18 -- 3
Week of 01
Feb 152 3 -- 109 76 -- --
14 Feb
2005 32 17 -- -- 5 30
mm 4
25-27 Feb
2005 61 4 24 2 19 1 mm 4
On 8 February 2005 a fissure about 1 km long appeared along the southern
slope. Vegetation along the fissure's margins had died, indicating that a
gas blow out had occurred there. On 14 February 2005 at 1830 another
explosion occurred. It was accompanied by significant seismic activity (see
table 2). This latest eruption ejected ash and glowing material as high as
50 m above the summit. Volcanic earthquakes were frequent.
Distances increased for electronic distance measurements (EDM) during
April, July, and October 2004 and during February 2005 (the last four
measurements). During 25-27 February 2005 ash plumes rose to 50 m high.
Volcano status remained at alert level 4 (the highest hazard status).
Background. Gunung Egon volcano sits astride the narrow waist of eastern
Flores Island. The barren, sparsely vegetated summit region has a
350-m-wide, 200-m-deep crater that sometimes contains a lake. Other small
crater lakes occur on the flanks of the 1,703-m-high volcano. A lava dome
forms the southern 1,671-m-high summit. Solfataric activity occurs on the
crater wall and rim and on the upper southern flank. Reports of historical
eruptive activity prior to explosive eruptions in 2004 were inconclusive. A
column of "smoke" was often observed above the summit during 1888-1891 and
in 1892. Strong "smoke" emission in 1907 reported by Sapper (1917) was
considered by the Catalog of Active Volcanoes of the World (Neumann van
Padang, 1951) to be an historical eruption, but Kemmerling (1929) noted
that this was likely confused with an eruption on the same date and time
from Lewotobi Lakilaki volcano.
Information Contacts: Dali Ahmad, Hetty Triastuty, Nia Haerani, and Sri
Kisyati, Directorate of Volcanology and Geological Hazard Mitigation
(DVGHM), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email:
dali@vsi.esdm.go.id; URL: www.vsi.esdm.go.id/).
Karangetang [Api Siau]
Siau Island, Indonesia
2.47°N, 125.29°E; summit elev. 1,784 m
All times are local (= UTC + 8 hours)
Ongoing seismicity continued at Karangetang during January-February 2005.
Lava avalanches were noted on 3 January and during the week of 17-23
January. The volcano was last discussed in a report on thermal alerts and a
pilot's report of an ash plume to 7.5 km altitude (Bulletin v 29, no.3,
which updated through May 2004). Table 3 presents a summary of the reported
seismic and other data during January and February 2005.
Table 3. A summary of observations made at Karangatang during 3
January-February 2005. Courtesy of DVGHM.
Date Volcanic Volcanic Multi- Emission Tremor Lava
Tectonic Alert
A B phase
Avalanches Level
03 Jan 3 10 2 2 0.5-3
mm 5 8 3
04 Jan 9 4 -- -- 0.5-1
mm -- 7 3
05
Jan 2 11 1 -- -- --
3 3
17-23
Jan 61 125 6 -- -- 36
36 3
Background. Karangetang (Api Siau) volcano lies at the northern end of the
island of Siau, N of Sulawesi. The 1784-m-high stratovolcano contains five
summit craters along a N-S line. Karangetang is one of Indonesia's most
active volcanoes, with more than 40 eruptions recorded since 1675 and many
additional small eruptions that were not documented in the historical
record (Catalog of Active Volcanoes of the World: Neumann van Padang,
1951). Twentieth-century eruptions have included frequent explosive
activity sometimes accompanied by pyroclastic flows and lahars. Lava dome
growth has occurred in the summit craters; collapse of lava flow fronts has
also produced pyroclastic flows.
Information Contacts: Dali Ahmad, Hetty Triastuty, Nia Haerani, and Sri
Kisyati, Directorate of Volcanology and Geological Hazard Mitigation
(DVGHM), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (Email:
dali@vsi.esdm.go.id; URL: www.vsi.esdm.go.id/).
Barren Island
Andaman Islands, Indian Ocean
12.278°N, 93.858°E; summit elev. 354 m
All times are local (= UTC + 5 ½ hours)
Members of the Indian Coast Guard observed a new eruption on the morning of
28 May 2005. An ash plume originated from a vent on the W side of the
summit of the central cone; fresh black lava flows did not reach the sea
(figure 8). The eruption continued through at least 6 June. Fresh lava
emissions had been noted by Indian Coast Guard personnel who patrol the
area regularly. A large amount of steam was emitted due to heavy rainfall
onto the hot lava surfaces. Heavy monsoon rains prevented access to the
island. However, the Geological Survey of India (GSI) was planning a
monitoring program and field expedition to the island.
Figure 8. Photograph of Barren Island erupting on 28 May 2005 taken from a
helicopter. The black lava in the foreground is of 1994-95 eruption. A lava
flow that did not reach the sea issues from a steaming flank vent. View is
towards the ESE. Courtesy of the Indian Coast Guard.
Dornadula Chandrasekharam (Indian Institute of Technology) noted on 6 July
that by that date the eruption had ceased, with only steam emissions
continuing after three weeks of heavy monsoon rains. The Indian Coast Guard
also confirmed to Chandrasekharam that the eruption was first noticed on 28
May, contrary to some press reports indicating that activity was seen on
the 27th. Patrol helicopters saw no activity on 25 and 26 May, and did not
observe the island on the 27th.
Press reports. A report in the 31 May edition of The Hindu stated that
defense forces witnessed intermittent billowing smoke and "flame" from the
volcano. The same article referenced a Press Trust of India (PTI) report
that military forces that landed on the island "experienced a hot breeze
and found themselves stepping on fresh lava" where earlier patrol teams had
been able to reach the crater. Another article from The Hindu reported that
on 2 June teams of the Indian Coast Guard vessel CG Sagar landed on the
island in an inflatable raft while a helicopter hovered overhead. The
report described eruptive activity consisting of lava and "fireballs" from
the crater every few seconds. The purpose of the expedition was to "collect
samples of the lava flowing into the rough sea" that would be given to
scientists. Coast Guard members and various other government officials made
an aerial survey of the island on 3 June according to a PTI report
published in The Hindu the next day. The Lt. Governor of Andaman, Ram
Kapse, saw "smoke and lava rising from the crater." Coast Guard sources
stated that the volume of "smoke" had increased and lava was still flowing
out of the crater.
A report in The Daily Telegrams on 17 February 2005 quoted K.N. Mathur,
Director General of the GSI, regarding a scientific visit to Barren Island
on 16 February. At that time, Mathur noted, the team observed "no serious
volcanic activities on the island." A similar report in the 18 February
edition of the Trinity Mirror carried a quote from Mathur that "There is no
activity in the crater and it remained as it was found during GSI's last
visit in 2003." These media reports were reproduced on the GSI website.
Background. Barren Island, a possession of India in the Andaman Sea about
135 km NE of Port Blair in the Andaman Islands, is the only historically
active volcano along the N-S-trending volcanic arc extending between
Sumatra and Burma (Myanmar). The 354-m-high island is the emergent summit
of a volcano that rises from a depth of about 2,250 m. The small,
uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with
walls 250-350 m high. The caldera, which is open to the sea on the W, was
created during a major explosive eruption in the late Pleistocene that
produced pyroclastic-flow and -surge deposits. The morphology of a fresh
pyroclastic cone that was constructed in the center of the caldera has
varied during the course of historical eruptions. Lava flows fill much of
the caldera floor and have reached the sea along the western coast during
eruptions in the 19th century and more recently in 1991 and 1995.
Information Contacts: Dornadula Chandrasekharam, Department of Earth
Sciences, Centre of Studies in Resources Engineering, Indian Institute of
Technology, Bombay 400076, India (Email: dchandra@geos.iitb.ac.in);
Geological Survey of India, 27 Jawaharlal Nehru road, Kolkata 700016, India
(URL: www.gsi.gov.in/barren.htm); The Daily Telegrams, India (URL:
www.and.nic.in/telegrame.htm); Trinity Mirror, Chennai, India; The
Hindu, 859 and 860 Anna Salai, Chennai 600002, Tamil Nadu, India (URL:
www.hinduonnet.com/); Press Trust of India, PTI Building, 4,
Parliament Street, New Delhi 110001, India (URL: www.ptinews.com/);
Indian Coast Guard, National Stadium Complex, New Delhi 110 001, India
(URL: indiancoastguard.nic.in/indian....HTML).
Long Valley
California, USA
37.70°N, 118.87°W; summit elev. 3,390 m
All times are local (= UTC - 8 hours)
The relative quiescence in Long Valley caldera that began in early 1999
persisted through 2004 according to the U.S. Geological Survey's weekly
reports and the 2004 annual summary of the Long Valley Observatory. Those
manuscripts provide the basis for this synopsis. Seismicity in the
adjacent Sierra Nevada block S of the caldera gradually died away over the
same period, although background levels remained somewhat higher than
within the caldera.
The resurgent dome continued to undergo minor fluctuations in deformation
as reflected in changes in the lengths of baselines onto the dome. Over the
past 6 years, the center of the resurgent dome has sustained the roughly
75-cm uplift that accumulated during the recurring unrest from 1979 through
1999.
Seismicity within both the caldera and the Sierra Nevada block to the S
remained low through 2004. The two most notable earthquake sequences within
the caldera were a minor swarm at the end of January and the first few days
of February in the S moat, and a M 3.0 earthquake on 20 September located
at the S margin of the caldera just N of Convict Lake. The latter was the
first earthquake greater than M 3.0 within the caldera since the cluster of
earthquakes on 4 November 2002, events centered beneath the S moat just S
of the Highway 395-203 junction. The swarm in early February 2004 was
located in the same general area of the S moat, but the epicenters fell
along a SW trend in contrast to the WNW trend shown by most earthquake
sequences in that area.
Seismicity within the adjacent Sierra Nevada block continued to be somewhat
elevated compared to that in the caldera through 2004. The Sierra Nevada
activity included about seven earthquakes over M 3, the largest of which
was an M 3.7 earthquake on 12 January 2004 located 2 km E of Red Slate
Mountain (19 km S of the caldera and 15 km WSW of Tom's Place). Most of the
activity remained concentrated in the NNE-trending aftershock zone
associated with the three earthquakes over M 5 during June and July 1998
and May 1999.
The most noteworthy seismic activity in the general vicinity of Long Valley
caldera during 2004 was the prolonged earthquake swarm in the Adobe Hills
centered roughly 20 km E of Mono Lake and 20 km NNE of Long Valley caldera
(figure 9). Its onset was marked by a M 2.3 earthquake at 0002 on 18
September, followed by M 3.2 and 4.1 earthquakes at 0007 and 0008,
respectively. Activity intensified through mid-afternoon of 18 September,
with M 5.5 and M 5.4 earthquakes at 1602 and 1643, respectively. These
produced widely felt shaking in the area from Bridgeport to Bishop.
Seismicity declined gradually through the remainder of the year and into
early 2005. By the end of December 2004, this Adobe Hill swarm had produced
well over 1,000 detectable earthquakes including ~48 over M 3 and 6 equal
or over M 4.
Figure 9. All earthquake epicenters detected in the Long Valley region for
2004. Courtesy of U.S. Geological Survey, Long Valley Observatory (2005).
The mid-crustal long-period (LP) volcanic earthquakes, which began beneath
the SW flank of Mammoth Mountain during the 1989 Mammoth Mountain
earthquake swarm, continued through 2004 but at a much reduced rate
compared with the peak in LP activity from early 1997 through mid-1998.
In early 2005 seismicity was generally minor (up to M 2.5) in and around
the caldera. An M 4.2 earthquake occurred S of Long Valley caldera on 13
March 2005 at 1409. The event, which produced light shaking in Mammoth
Lakes and Bishop was located in the Sierra Nevada ~12 miles SW of Toms
Place near Grinnell Lake. It was followed by a series of 18 aftershocks,
the largest which were M 2.8 and M 2.3. The last earthquake of similar
magnitude in this area occurred in 1999 on 17 May. In addition to the M 4.2
main shock/aftershock sequence, two other significant earthquakes occurred
in the Adobe Hills area E of Mono Lake, and a third occurred on 13 March in
the Sierra Nevada S of the caldera, near Mount Baldwin. All three had
magnitudes under M 2.0. From that time to mid-June 2005, seismicity was
generally in the range of M 1-2, with a very few occurring to M 3.
Carbon dioxide (CO2) concentrations measured in the Horseshoe Lake
tree-kill area on the S flank of Mammoth Mountain showed no significant
changes for 2004 with respect to the past several years. A survey of
scattered areas of vegetation die-off and diffuse CO2 flux on the resurgent
dome completed in 2004 indicated anomalous CO2 emissions from the kill
areas were ~9 metric tons/day (compared with ~300 tons/day from Mammoth
Mountain). The d^13C-CO2 values of the diffuse emissions were similar to
values previously reported for CO2 from hot springs and thermal wells
around Long Valley, indicating a common source. The areas of elevated CO2
flux tend to be associated with locally elevated soil temperatures. Some of
the older areas near the Casa Diablo power plant are likely related to
geothermal power production, but development of new areas may reflect a
delayed response of the hydrothermal system to the 1997 unrest episode
(including an additional 10-cm uplift of the resurgent dome accompanied by
intense earthquake swarm activity in the S moat).
Thermal spring discharge in Hot Creek Gorge, which had dropped by about 20%
in the last half of 2003, followed by a recovery beginning in January 2004,
reached normal discharge values by June 2004.Fluid levels in key monitoring
wells continued to decline, with some wells reaching their lowest values
since records began in 1985.
Background. The large 17 x 32 km Long Valley caldera E of the central
Sierra Nevada Range formed as a result of the voluminous Bishop Tuff
eruption about 730,000 years ago. Resurgent doming in the central part of
the caldera occurred shortly afterwards, followed by rhyolitic eruptions
from the caldera moat and the eruption of rhyodacite from outer ring
fracture vents, ending about 50,000 years ago. During early resurgent
doming the caldera was filled with a large lake that left strandlines on
the caldera walls and the resurgent dome island; the lake eventually
drained through the Owens River Gorge. The caldera remains thermally
active, with many hot springs and fumaroles, and has had significant
deformation, seismicity, and other unrest in recent years. The
late-Pleistocene to Holocene Inyo Craters cut the NW rim of the caldera,
but are chemically and tectonically distinct from the Long Valley system.
Reference: U.S. Geological Survey-Long Valley Observatory, 2005, Long
Valley Observatory Quarterly Report, October-December 2004 and Annual
Summary for 2004 (URL: lvo.wr.usgs.gov/).
Information Contacts: Long Valley Observatory, U.S. Geological Survey, 345
Middlefield Rd., MS 977, Menlo Park, CA 94025, USA (URL:
lvo.wr.usgs.gov/).
Reventador
Ecuador
0.078°S, 77.656°W; summit elev. 3,562 m
All times are local (= UTC - 5 hours)
Crisis escalates. Instituto Geofisico (IG) members noted that eruptions at
Reventador in Ecuador's eastern cordillera continued into at least early
July 2005. Observers documented thick blocky lava flows, occasional
Vulcanian explosions, new fumarolic activity on the N flank of the cone,
and venting of vapor, gases, and fine ash. This followed a spate of
increased seismicity during April to early June 2005. Lava flows had
extended 4 km from the summit vent toward the SE, in the direction of the
main highway across this region, a route that links the important oilfields
in the Amazon basin with Quito, the capital. The lava flows were
sequentially numbered (Lava #3, #4, etc.).
Lava #3, a flow that began in November 2004 (Bulletin v. 29, no. 11),
advanced slowly and ceased movement by early January 2005. Following
relatively low seismic activity in late 2004 and early 2005, the IG
monitoring network began to register bands of harmonic tremor starting 1
April (figure 10). Through 8 April 2005, instruments recorded 45 tremor
episodes, each lasting 10 to 60 minutes. Dominant frequency peaks were
between 1 and 1.5 Hz. Given that strong incandescence was observed by a
guard of PetroEcuador from 14 km away, the tremor was interpreted to signal
the rise of magma into the upper part of the cone through an open conduit.
Lava #4 erupted coincident with this strong tremor and was the most
important surface manifestation. It was first observed in an overflight on
12 April, escaping from a summit crater conduit that had formed a
carapace. It was seen flowing down the SW crater notch onto the cone's
flanks and then onto the SW and SE caldera floor. The flow partially
covered Lava #3 (figure 11), resulting in layers of recent lava in some
places reaching more than 50 m thick. This emplacement was observed during
several days of work on the seismic instrumentation and sampling within the
caldera carried out by IG personnel during 19-22 April. During the same
overflights, a new fumarole field was observed on the lower S flank of the
cone, a spot very close to the upper Reventador River, in the same place
where thermal anomalies were observed on 11 March 2005.
Figure 10. Seismic events registered at Reventador since August 2004.
Courtesy of IG.
Figure 11. Location of lava flows related to eruptive activity within the
Reventador caldera since 2002. Photo taken looking at the SE flank on 6
May 2005 by P. Ramon. Provided courtesy of IG.
Starting on 15 May there was an important increase in the intensity of
harmonic tremor, often preceded by low frequency (< 1 Hz) long-period
events, a conspicuous aspect of behavior that was absent in April. Many of
the long-period events, particularly those occurring during 17-21 May, were
of such magnitude that they registered at seismic stations on other
volcanoes (e.g., Cerro Negro and Guagua Pichincha) more than 100 km distant.
After this elevated activity in mid May, there was a decrease in the number
of events, dropping to an average of 88 per day. During this period Lava
#4 continued to flow, moving at the rate of about 20 m/day, advancing
particularly strongly along the caldera's S wall in a stream channel (Rio
Marker) cut through the 2002 pyroclastic deposits. Lava reached 25 meters
thick when seen during a 22-23 May visit, during which time strong roars
and the sounds of 'many jet planes' blared from the vent. These sounds
indicated a strong gas flux, although little vapor was observed. At this
time, there was an absence of both explosions and incandescence in the
summit crater.
An overflight on 25 May confirmed the emergence of a new flow (Lava
#5). It followed the same route as #4, but was comprised of three
principal lobes. The middle lobe, which represented the most conspicuous
and largest volume, advanced down the Rio Marker's channel (figure 12).
Figure 12. Lavas 4 and 5 flowing down the Marker's stream channel along the
SE margin of Reventador's caldera. Photo taken on 17 June 2005 by P.
Ramon. Provided courtesy of IG.
Reventador's activity in June 2005 began with an important swarm of
volcano-tectonic and hybrid seismic events-starting on the 2nd and
continuing through the 3rd. Of particular note, tremor continued for more
than 10 hours, and provided background to the discrete volcano-tectonic and
hybrid events Hybrid events had not been registered since November
2004. Following these important swarms, instruments registered strong,
full-amplitude bands of spasmodic tremor, comprised to some extent by
packages of long-period events lasting for hours to days on end.
During these early days of June, there was an intensification of
incandescence in the crater and later, the emission of gases and slight
ash. On 8 June, a 100 km long vapor/ash column extended from the volcano
into the S part of Quito at ~7 km altitude and caused a very slight
powdering of ash, which was brought down by a gentle rain and left cars
dappled with circular spots.
A trip by IG volcanologists into the caldera on 11-12 June disclosed strong
Strombolian fountaining in the summit crater. Lava #5 continued to flow
atop the stalled Lava #4. Measurements of SO2 flux with a mini-DOAS
(differential optical absorption spectroscopy) resulted in an estimate of
~2,500 metric tons/day.
Three other seismic stations were installed around the caldera with the
helicopter help of the petroleum company OCP during 16-19 June. One
broad-band seismograph and infrasound system was also installed, thanks to
collaboration with Jeff Johnson of the University of New Hampshire. During
this period no Strombolian activity was observed, but Vulcanian explosions
(figure 13) occurred with little warning. A 24-hour period during 18-19
June included at least seven discrete explosions, producing strong
infrasound and seismic responses. Many of these explosions discharged
columns that rose 2-3 km above the summit (and some, up to as high as ~6 km
above the summit) and were clearly heard within the caldera. Large
incandescent blocks could be seen thrown several hundreds of meters into
the air, falling on the cone's upper slopes. Ash content in the columns
was moderate. Explosions were discrete and often terminated within 4
minutes. Thermal alerts were identified by the Hawaii Institute of
Geophysics and Planetology (HIGP). Observations on 30 June and 1 July
noted recent lava flows in the upper Marker river valley (figure 14).
Figure 13. One of Reventador's discrete Vulcanian explosions observed
during a 19 June 2005 helicopter flight. The view is from the E of
Reventador caldera looking toward the W. Photo taken on by P. Ramon;
provided courtesy of IG.
Figure 14. A photo of Reventador's Lava #4 flow front (which had reddish
hues) overtopped by Lava #5 (more nearly white). The shot was taken in the
Rio Marker at 1100 on 30 June 2005. By 1 July, Lava #5 had still not
advanced beyond the terminus of Lava #4. Photo by P. Ramon, provided
courtesy of IG.
The 4-6 discrete explosive degassing events/day observed in June led the IG
authors to surmise that there were a series of temporary plugs in the upper
part of the conduit. This behavior was thought to reflect magma becoming
more crystal rich.
As of 6 July, harmonic tremor, occasional explosions, and long-period and
volcano-tectonic signals all continued to register at Reventador on the
IG's telemetered monitoring network. Strong Strombolian fountaining was
observed from distances of 6.5 and 14 km during the evening and one of the
lobes of Lava #5 was advancing down the caldera wall (following the Rio
Marker), but abruptly slowed to perhaps only ~20 m/day. In comparison, this
flow-front velocity had earlier attained ~70 m/day (during 19-23 June) and
~50 m/day (during 23-30 June). The diminished rate of advance and
continuing high-amplitude tremor suggested that perhaps a new lava flow
(Lava #6) had broken out high on the flanks, a conjecture yet to be
confirmed by press time. Lava #5 was still 1.2 km from the steep incline, a
point where it could begin rapid descent to the alluvial fan where the
highway and petroleum pipeline are located.
Background. Reventador is the most frequently active of a chain of
Ecuadorian volcanoes in the Cordillera Real, well E of the principal
volcanic axis. The forested dominantly andesitic stratovolcano rises to
3,562 m above the remote jungles of the western Amazon basin. A 4-km-wide
caldera widely breached to the E was formed by edifice collapse and is
partially filled by a young, unvegetated stratovolcano that rises about
1,300 m above the caldera floor to a height above the caldera rim.
Reventador has been the source of numerous lava flows as well as explosive
eruptions that were visible from Quito in historical time. Frequent lahars
in this region of heavy rainfall have constructed a debris plain on the
eastern floor of the caldera. The largest historical eruption at Reventador
took place in 2002, producing a 17-km-high eruption column, pyroclastic
flows that traveled up to 8 km, and lava flows from summit and flank vents.
Information Contacts: Patricia Mothes, Patricio Ramon, Pete Hall, Daniel
Andrade, and Liliana Troncoso, Geophysical Institute (IG), Escuela
Politecnica Nacional, Apartado 17-01-2759, Quito, Ecuador (URL:
www.igepn.edu.ec/; Email: pmothes@igepn.edu.ec; pramon@igepn.edu.ec;
mhall@igepn.edu.ec; dandrade@igepn.edu.ec; ltroncoso@igepn.edu.ec); Jeffrey
B. Johnson, Dept. of Earth Sciences, James Hall University of New
Hampshire, Durham, NH 03824, USA (Email: jeff.johnson@unh.edu).
Lascar
northern Chile
23.37°S, 67.73°W; summit elev. 5,592 m
All times are local (= UTC - 4 hours)
The 4 May 2005 early morning eruption of Lascar was described in Bulletin
v. 30, no. 4. Note that the time conversion in that issue was in error by 1
hour. The following information is based on a report prepared for Bulletin
staff by Jose Viramonte of the Universidad Nacional de Salta, and Lizzette
Rodriguez of Michigan Technological University.
Viramonte and Rodriguez estimated that the 4 May 2005 eruption column rose
to a height of ~10-11 km, based on numerical models of temperature and wind
measurements from the Servicio Metereologico Nacional, Argentina at
different altitudes at the time of the eruption. The column traveled
rapidly to the SE under the influence of the strong tropospheric winds with
predominant direction from the NW to the SE.
Residents of the towns of Talabre (located 15 km W of the volcano) and Jama
(located 60 km ENE of the volcano) did not report earthquakes or
explosions. The Instituto GEONORTE of the Universidad Nacional de Salta
reported very fine ashfall at 0545 in the city of Salta, located ~285 km
SSE of the volcano. Ash sample collection, carried out by GEONORTE
personnel for 2.5 hours, measured a rate of 0.4 g/ (m²h). Grain size
analyses of the ash showed a strong mode at diameters of 4-8 phi
(0.062-0.003 mm) (figure 15); the ash was composed predominantly of
andesitic lithic fragments and broken crystals of two pyroxenes (hyperstene
and augite) and plagioclase, with very scarce glass shards.
Figure 15. Histogram of the grain size of ash deposited at the city of
Salta by the 4 May 2005 Lascar eruption. Courtesy of Jose Viramonte and
Lizzette Rodriguez.
The Buenos Aires VAAC and the Comision Nacional de Actividades Espaciales
(CONAE) processed different bands from MODIS data: b29-b32 for SO2, b31-b32
for ash, and b30-b32 for SO4. The first two band combinations showed the
Lascar plume in coincidence with the b5-b4 band combination from NOAA-17
(figure 16).
Figure 16. NOAA-17 image of a SE-directed plume from Lascar at 1440 UTC
(1040 local time), obtained with the difference of channels 4 and 5 from
the AVHRR sensor. The plume can be better identified withing the ellipse on
higher resolution reproductions. Courtesy of Jose Viramonte and Lizzette
Rodriguez.
The grain size and shape of the ash, its composition, and the
interpretation of the satellite data, suggest that Lascar volcano had a
short phreato-vulcanian eruption.
On May 25, Felipe Aguilera of the Universidad Catolica del Norte,
Antofagasta, Chile, climbed up to the crater of Lascar volcano (figure 17).
He reported three new strong fumaroles a few meters from the S border of
the crater, and sampled the sulfur sublimates (figure 18). No new bombs or
blocks were seen around the crater area.
Figure 17. View of Lascar's NE crater, looking NE (see arrow, upper left)
with fumaroles present along a number of fractures to the N and E sides.
The active crater is just out of view in the image foreground. Picture
taken by Felipe Aguilera on 25 May 2005. Courtesy of Jose Viramonte and
Lizzette Rodriguez.
Figure 18. Schematic diagram showing the position of fumaroles on Lascar
after the eruption on 4 May 2005. Also indicated are several new
post-eruption fumaroles that developed on the S crater margin. Courtesy of
Jose Viramonte and Lizzette Rodriguez.
Recent and future work. A team of scientists from Michigan Technological
University, the University of Hawaii, the Universidad Nacional de Salta,
the Universidad de Chile, and the Universidad Nacional de Cordoba,
conducted a field campaign at Lascar from 29 November to 8 December 2004.
During this period, SO2 emissions were measured using two mini-UV
spectrometers; aerosols were measured using two Microtops II sun
photometers, and temperatures of the vent fumaroles were measured using a
Forward Looking IR Radiometer (FLIR). Preliminary processing of the gas
data showed a decrease since 2003 in the emissions, with SO2 fluxes around
500 tons/day (Rodriguez et al., 2005). This contrasts with the fluxes
determined by Mather et al. (2004) on January 2003, which were on the order
of 2,300 tons/day. Observations of the SO2 index, using ASTER TIR images,
have shown a decrease in the size of the SO2 anomaly from 2000 to the first
half of 2004 (Castro Godoy and Viramonte, 2004).
Temperature measurements made at the crater on 2 December 2004 by
University of Hawaii scientists using a FLIR indicated low temperatures for
the fumarole field, which represented a decrease when compared with the
results of direct measurements conducted in October 2002 by Franco Tassi
and others (Tassi et al., 2004; Bulletin v. 28, no. 3). Similar
observations have been made using ASTER SWIR and TIR images (Silvia Castro,
GEOSAR-AR program), which have shown a decrease in the absolute
temperatures and the size of the thermal anomaly since October 2002 (Castro
Godoy and Viramonte, 2004). Images during the month of April 2005 showed a
slight increase in the area and maximum temperature of the anomaly at the
beginning of the month, followed by a decrease at the end of April, prior
to the eruption. Decreases in the thermal activity have been observed in
previous eruptive cycles, prior to explosive events (Oppenheimer et al.,
1993; Matthews et al., 1997).
The data collected during the 2004 field campaign will help in the
understanding of the pre-eruptive conditions at Lascar. SO2 emission rates
on 7 December 2004 will be used to ground truth the satellite data from an
ASTER overpass at 1436 UTC (1036 local time), and recently acquired ASTER
data will be used to investigate SO2 emissions during the period close to
the 4 May 2005 eruption. Scientists from Universita degli studi di Firenze
(Italy), Universidad Catolica del Norte (Chile), and Universidad Nacional
de Salta (Argentina) are conducting a systematic gas sample campaign at
Lascar and other active volcanoes on the Central Volcanic Zone. Finally,
scientists from the Universidad Catolica del Norte and the Universidad
Nacional de Salta are processing data from Landsat TM and ETM+ images, with
the objective of understanding the behavior of Lascar volcano during the
1998-2004 period.
References: Castro Godoy, S. and Viramonte, J.G., 2004, Micro FTIR field
measurement for volcanic mapping, SO2 and temperature monitoring using
ASTER images in Lascar Volcano, southern central Andes: IAVCEI General
Assembly, Book of Abstracts, Pucon, Chile, 14-20 November.
Mather, T.A., Tsanev, V.I., Pyle, D.M., McGonigle, A.J.S., Oppenheimer, C.,
and Allen, A.G., 2004, Characterization and evolution of tropospheric
plumes from Lascar and Villarrica volcanoes, Chile: Journal of Geophysical
Research, v. 109.
Matthews, S.J., Gardeweg, M.C., and Sparks, R.S.J., 1997, The 1984 to 1996
cyclic activity of Lascar volcano, northern Chile: cycles of dome growth,
dome subsidence, degassing and explosive eruptions: Bulletin of
Volcanology, v. 59, p.72-82.
Oppenheimer, C., Francis, P., Rothery, D., Carlton, D., and Glaze, L.,
1993, Interpretation and comparison of volcanic thermal anomalies in
Landsat Thematic Mapper infrared data: Volcan Lascar, Chile, 1984-1991:
Journal of Geophysical Research, 98, p. 4269-4286.
Rodriguez, L.A., Watson, I.M., Viramonte, J., Hards, V., Edmonds, M.,
Cabrera, A., Oppenheimer, C., Rose, W.I., and Bluth, G.J.S., 2005, SO2
conversion rates at Lascar and Soufriere Hills volcanoes: 9th Gas Workshop,
Palermo, Italy, May 1-10.
Tassi, F., Viramonte, J., Vaselli, O., Poodts, M., Aguilera, F., Martinez,
C., Rodriguez, L.A., and Watson, I.M., 2004, First geochemical data from
fumarolic gases at Lascar volcano, Chile: 32nd International Geological
Congress, Florence, August 20-28, 2004.
Background. Lascar is the most active volcano of the northern Chilean
Andes. The andesitic-to-dacitic stratovolcano contains six overlapping
summit craters. Prominent lava flows descend its NW flanks. An older,
higher stratovolcano 5 km to the E, Volcan Aguas Calientes, displays a
well-developed summit crater and a probable Holocene lava flow near its
summit (de Silva and Francis, 1991). Lascar consists of two major edifices;
activity began at the eastern volcano and then shifted to the western cone.
The largest eruption of Lascar took place about 26,500 years ago, and
following the eruption of the Tumbres scoria flow about 9,000 years ago,
activity shifted back to the eastern edifice, where three overlapping
craters were formed. Frequent small-to-moderate explosive eruptions have
been recorded from Lascar in historical time since the mid-19th century,
along with periodic larger eruptions that produced ashfall hundreds of
kilometers away from the volcano. The largest historical eruption of Lascar
took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit
and ashfall in Buenos Aires.
Information Contacts: Raul Becchio and Jose G. Viramonte, Instituto
GEONORTE and CONICET, Universidad Nacional de Salta, Buenos Aires 177,
Salta 4400, Argentina (Email: viramont@unsa.edu.ar; URL:
www.unsa.edu.ar/natura/); Lizzette A. Rodriguez and Matthew Watson,
Michigan Technological University, Houghton, MI 49931, USA (Email:
larodrig@mtu.edu; URL: www.geo.mtu.edu/volcanoes/); Felipe Aguilera,
Universidad Catolica del Norte, Avenida Angamos 0610, Antofagasta, Chile
(Email: faguilera@ucn.cl; URL: www.ucn.cl/FacultadesInstitutos/
Fac_geologia.asp); Silvia Castro Godoy, GEOSAT-AR Project, SEGEMAR, Buenos
Aires, Argentina (Email: silvia_castro_godoy@hotmail.com, URL:
www.segemar.gov.ar/sensores...tos.htm); Matt Patrick and
Rob Wright, HIGP-University of Hawaii, Honolulu, HI 96822, USA (Email:
patrick@higp.hawaii.edu; URL: www.higp.hawaii.edu/volcanology.html);
Sergio Haspert and Ricardo Valenti, VAAC Buenos Aires - Div. VMSR, Servicio
Meteorologico Nacional, Argentina (Email: vmsr@meteo.edu.ar, URL:
www.meteofa.mil.ar/).
Rotorua
New Zealand
38.08°S, 176.27°E; summit elev. 757 m
All times are local (= UTC + 11 hours)
Bulletin v. 26, no. 3 reported hydrothermal activity at Rotorua on 26
January 2001 involving the ejection of mud and ballistic blocks. Bulletin
v. 28, no. 12 reported that the New Zealand Institute of Geological and
Nuclear Sciences reported two subsequent hydrothermal eruptions in Rotorua
caldera at Kuirau Park around 1100 on 6 November 2003 (figure 19). The
eruptions occurred just meters from the site of the large blowout in 2001.
The area is known for this kind of geothermal activity. The following
information is primarily from Ashley Cody.
Figure 19. Rotorua is the NW-most caldera of the Taupo volcanic zone, in
the Bay of Plenty region of New Zealand's North Island. Courtesy of UNAVCO.
In late May 2004 a geothermal well ~40 m deep at Tokaanu on Lake Taupo
(~100 km S of Rotorua) blew out suddenly, erupting mud and scalding waters
to ~15 m high and flooding surrounding properties for several days until it
could be quenched and a new headworks fitted. This well may have been
standing open and just suddenly began boiling, since its casing seemed to
be intact.
About 0100 on Saturday 29 June 2004 the blowout of a geothermal well in
Rotorua blew muddy water and rubbly debris to ~15 m high and showered muck
over houses and cars to a radius of ~100 m accompanied by noise "like a jet
aircraft." It went on until about 0400 on 30 June 2004 when it was quenched
with a pumped cold water supply. It was cement-grouted shut a few days
later. The well was 100 m deep and cased to 47.5 m.
Starting 18 July 2004 in the early afternoon, many earthquakes were
strongly felt by many people in the area ~30 km N of Rotorua and ~20 km NW
from Kawerau, in the northern North Island, or central Bay of Plenty. By 23
July more than 200 earthquakes were recorded in this area, most at less
than 10 km depth.
In Lake Rotoehu, about 20 km N of Rotorua city, eyewitnesses reported a
water column 100 m high that occurred at the same time as a strongly-felt
ML 5.4 earthquake at about 1600 on 18 July 2004 at ~5 km depth. Shortly
afterward a big series of waves occurred on the lake, and swept up beaches
much higher than ever seen before.
Ground rupturing was reported at several sites along southern shores of
Lake Rotoehu. Many houses were evacuated due to damage such as walls
breaking apart and houses shifting off their foundations. The main road was
blocked in many places and more than 200 houses were evacuated due to their
becoming unsafe to live in. Several people were killed by trees falling
down banks onto cars and houses during the earthquakes.
On Thursday 17 March 2005 at about 1435, a blowout was observed from the
northern end of Ruapeka Bay on Lake Rotorua, at Ohinemutu. It shot dark
grey muddy waters and steam to ~6 m for 3-4 minutes. An eyewitness called
the council safety inspector, Peter Brownbridge. On 18 March at about 1500,
the safety inspector saw two more shots each ~1 m high from the same spot
in the lake. This previously unknown vent is ~25 m NW from a clear flowing
hot spring known simply as S1233, in the bed of the lake just 10 m W of the
tip of Muruika Point. This is where a prehistoric account relates of a
sunken village, where a sudden disturbance occurred one night and many
people were killed. From verbal genealogy records, this event may have
occurred about early 1700s-1720s. Today rows of timber posts are still
standing below water level in the lake here.
According to a report in The Dominion Post by Mike Watson on 21 April 2005,
one of the largest hydrothermal eruptions in the Rotorua area since 1948
took place about 1030 on 19 April 2005 and was witnessed by two farmers
(figure 20).
Figure 20. The geothermal eruption roughly midway between Rotorua and Taupo
on 19 April 2005 left a 50-m wide crater. Courtesy of Ashley Cody.
A huge column of hot steam, mud and rocks was thrown 200 m in the air. The
eruption happened in an inaccessible area at Ngatamariki scenic reserve,
close to the Waikato River, and about 8 km from Orakei Korako geothermal
springs, roughly halfway between Taupo and Rotorua. The column was visible
10 km away and left a 50 m-wide crater and two hectares of debris. With the
energy now taken out of the vent, no further eruption was expected.
The major part of the eruption lasted about two hours but it was still
spewing steam up to 10 m high five hours later. The eruption sent out
7,000-10,000 m^3 of material. Mud and 50 cm-diameter rocks covered a 70-100
m radius from the crater site, which had previously been covered by 2
m-high blackberry bushes and fallen trees (figure 21). The ground may take
months to cool. According to Ashley Cody, the site had been heating up in
the past year, with three new hot springs forming.
Figure 21. The hydrothermal eruption roughly halfway between Taupo and
Rotorua left ash and mud covering the surrounding area to a depth of 4 m
(light-colored material on ground surface, coating some trees, and choking
the stream). Courtesy of Ashley Cody.
Background. The 22-km-wide Rotorua caldera is the NW-most caldera of the
Taupo volcanic zone. Rotorua is the only single-event caldera in the Taupo
volcanic zone and was formed about 220,000 years ago following eruption of
the >340 km^3 rhyolitic Mamaku Ignimbrite. Although caldera collapse
occurred in a single event, the process was complex and involved multiple
collapse blocks. The major city of Rotorua lies at the S end of the lake
that fills much of the caldera. Post-collapse eruptive activity, which
ceased during the Pleistocene, has been restricted to lava dome extrusion
without major explosive activity. The youngest eruptive activity at Rotorua
consisted of the eruption of three lava domes less than 25,000 years ago.
The major thermal areas of Takeke, Tikitere, Lake Rotokawa, and
Rotorua-Whakarewarewa are located within the caldera or outside its rim.
Whakarewarewa contains New Zealand's last remaining active geyser field.
Information Contacts: Ashley Cody and Ron Keam, Physics Department, The
University of Auckland, Private Bag 92-019, Auckland, New Zealand (Email:
ashley.cody@wave.co.nz, r.keam@auckland.ac.nz); Mike Watson, The Dominion
Post.
White Island
New Zealand
37.52°S, 177.18°E; summit elev. 321 m
All times are local (= UTC + 11 hours)
White Island was last reported on in Bulletin v. 29 no. 3, covering the
period to March 2004. At that time, approximately two years had passed
since any significant eruption, but the New Zealand Institute of Geological
and Nuclear Sciences (GNS) continues to monitor White Island. This report
is a summary of their brief reports.
From April 2004 until June 2005, seismicity and hydrothermal activity at
White Island remained at low levels, with some brief periods of weak to
moderate volcanic tremor recorded during September to November of 2004. The
level of the crater lake has risen significantly over this period, from
12-13 m below the overflow level in April 2004 to only 3-4 m below overflow
level in June 2005 (figure 22). Some of this increase was caused by
landslides in July 2004 and by heavy rains in May 2005. Steam and gas
emissions have been minor, with the exception of a large plume visible from
the mainland on 15 October 2004. The alert level remained at 1 (on a scale
of 0-5), indicating some degree of unrest but no threat of eruption.
Figure 22. The crater lake on White Island, taken 9 January 2005, when the
lake level was about 5 m below the overflow level and rising. Courtesy of
Franz Jeker.
Background. Uninhabited 2 x 2.4 km White Island, one of New Zealand's most
active volcanoes, is the emergent summit of a 16 x 18 km submarine volcano
in the Bay of Plenty about 50 km offshore of North Island. The 321-m-high
island consists of two overlapping andesitic-to-dacitic stratovolcanoes;
the summit crater appears to be breached to the SE because the shoreline
corresponds to the level of several notches in the SE crater wall. Volckner
Rocks, four sea stacks that are remnants of a lava dome, lie 5 km NNE of
White Island. Intermittent moderate phreatomagmatic and strombolian
eruptions have occurred at White Island throughout the short historical
period beginning in 1826, but its activity also forms a prominent part of
Maori legends. Formation of many new vents during the 19th and 20th
centuries has produced rapid changes in crater floor topography. Collapse
of the crater wall in 1914 produced a debris avalanche that buried
buildings and workers at a sulfur-mining project.
Information Contacts: Institute of Geological and Nuclear Sciences (GNS),
Private Bag 2000, Wairakwi, New Zealand (URL: www.gns/cri.nz);
GeoNet, a project sponsored by the New Zealand Government through these
agencies: Earthquake Commission (E.C.), Geological and Nuclear Sciences
(GNS), and Foundation for Research, Science and Technology (FAST). Geonet
can be contacted at the above GNS address (URL:
www.geonet.org.nz/contact.htm); Franz Jeker, Rigistrasse 10, 8173
Neerach, Switzerland (Email: franz.jeker@swissonline.ch).
__________________________________________________________
Global Volcanism Program, NHB E-421 Tel: (202) 633-1800
Smithsonian Institution Fax: (202) 357-2476
Washington, DC 20560-0119 Email: gvp@si.edu
Internet: www.volcano.si.edu/
-
Re: GVN Bulletin
Thu, August 18, 2005 - 1:23 AM****************************************************
Bulletin of the Global Volcanism Network, June 2005
****************************************************
From: Ed Venzke <venzke@volcano.si.edu>
Bulletin of the Global Volcanism Network
Volume 30, Number 6, June 2005
Colima (Mexico) Explosions through June 2005,
with repeated dome growth and destruction
Soufriere Hills (Montserrat) Abundant ash-laden
plumes, pyroclastic flows, and local ashfall
St. Helens (Washington, USA) Extrusion of
smooth-surfaced dome lavas that later crumbled; explosions
Ebeko (Kurile Islands, Russia) Small ash deposits
in January 2005 but plumes later became infrequent
Shiveluch (Kamchatka, Russia) Lava dome growth,
ash falls, pyroclastic flows during early to mid-2005
Karymsky (Kamchatka, Russia) Several ash plumes,
including two to ~ 8 km altitude, during mid-2005
Canlaon (Philippines) May 2005 ash ejections
ceasing after the 25th as monitored parameters declined
Kilauea (Hawaii, USA) During November
2004-January 2005 lava flows continued to enter the sea
Tungurahua (Ecuador) Ash plumes and LP earthquakes still common in 2004-2005
McDonald Islands (S Indian Ocean) Satellite
infrared data suggests a new unwitnessed eruption
Editors: Rick Wunderman, Catherine Galley, Edward Venzke, and Gari Mayberry
Volunteer Staff: Robert Andrews, William Henoch,
Jacquelyn Gluck, Jerome Hudis, and Stephen Bentley
Colima
Mexico
19.514°N, 103.62°W; summit elev. 3,850 m
All times are local (= UTC - 6 hours)
Small to moderate explosive eruptions have been
common at Colima since 1999, some blasting
material as high as 11 km altitude and at times
sending pyroclastic flows to 5 km runout
distances. Between these explosive eruptions,
andesitic lava from the main intracrater vent
sometimes formed small, short-lived lava domes.
The feeder lavas, cryptodomes, and occasional
domes were blasted out during subsequent
eruptions. A table of significant eruptive events
at Colima during July 1999 to June 2005 (Luhr and
others, in press) produced this tally for the
number of days where plumes went over 2 km above
the summit (~6 km altitude): in the latter half
of 1999, three days; 2000, one day; 2001, four
days; 2002, four days; 2003, 15 days; 2004, ~24
days; and in the first half of 2005, 31 days.
Eruptions discussed in aviation reports from the
Washington Volcanic Ash Advisory Center (VAAC)
became a significant source of data starting in
2003, and formed the basis of many entries in the subsequent years.
Extrusions during September-November 2004 formed
a new lava dome in the active crater, and two
lava flows descended from that crater along the N
and WNW flanks (BGVN 30:01). After lava effusion
ceased, intermittent explosions and exhalations
followed. In the same pattern mentioned above,
the dome was later destroyed by Vulcanian-style
explosions that produced eruption plumes and in
some cases, pyroclastic flows (BGVN 30:03).
The number of seismic events decreased during
December 2004-February 2005 (figure 1), and with
some important exceptions, remained under 10
events per day until as late as the end of June
2005. During this reporting interval, April-June
2005, intermittent explosions continued (figure
1). Explosions that generated pyroclastic flows
were known to have continued through at least 5 July.
Figure 1. The number of daily earthquakes
ascribed to rockfalls and pyroclastic flows
(heavy line) and to explosions and exhalations
(dashed line) at Colima during September
2004-June 2005. Double arrows show the beginning
(B) and the end (E) of the lava extrusion in late
2004. A label indicates the period when
occasional large explosions took place (an
interval that began on 10 March and continued
through June 2005). Courtesy of Colima Volcano Observatory.
Comparatively large explosions began to occur
starting 10 March 2005 (BGVN 30:03). The largest,
accompanied by pyroclastic flows, were
particularly vigorous from 24 May to 5 June. As
in March 2004 the explosions consisted of
Vulcanian-style gas-and-ash explosions. Some of
the April-June explosions issued material that
reached as high as ~10 km altitude, and
pyroclastic flow runout distances reached up to
~5.1 km, an increase over those in March 2004
(when maximum runout distances only reached ~2.8 km).
When photographed on 25 May 2005 the dome and
unconsolidated material filled much of the
crater, although the intracrater area was
anything but flat (figure 2). By comparison, a
photo of the crater taken on 16 June 2005,
following many large Vulcanian explosions, shows
its upper portion to be essentially empty (figure 3).
Figure 2. At Colima on 25 May 2005 the crater
contained considerable dome and unconsolidated
material, filling it to near the rim. Several
weeks later, after further explosions had driven
considerable material out, the upper crater was
left with substantial open space (see next
photo). Courtesy of Colima Volcano Observatory.
Figure 3. Photo of Colima's crater after the
comparatively large explosions that began in
March 2005. This photo was taken on 16 June
looking from the S. Eruptions had removed much of
the crater fill and a small dome from the upper
crater. Small impact craters pocked the crater
floor. An erosion channel had developed across
crater's S rim, presumably due to the passage of
pyroclastic flows associated with the recent
explosions. The notch in the rim has been
prominent since 2004 and has emptied and perhaps
grown considerably since the photo taken 25 May
2005. Despite the changes seen in this photo, the
explosions had left the crater walls intact and
without evidence of fractures. Courtesy of Colima Volcano Observatory.
The March-June explosive sequence removed the
2004 lava dome, and left a crater ~260 m across
and ~30 m deep (figure 3). No significant
deformation of the volcanic edifice was recorded
before or during the large explosions (table 1).
After the explosion of 5 June, residents were
evacuated from Juan Barragan, a small village ~10
km SE of the summit. Smaller explosions at Colima
typically take place at the rate of several per day.
Table 1. Main characteristics of the largest
explosions seen at Colima during May-June 2005.
Column heights and ash cloud velocities came from
remote-sensing data and reports furnished by the
Washington VAAC. The highest velocity, 15 m/s,
corresponds to 54 km/hour. Courtesy of Colima Volcano Observatory.
Time of Altitude of Direction
and average Length of the Length of
explosion (UTC) the column horizontal
velocity ash cloud in km* pyroclastic flows
of the ash cloud
24 May (0009) 9.7 km W (7.7
m/s) 204 km 3.5 km
30 May (0826) 8.5 km SE (15
m/s) 102 km 4 km
02 Jun (0449) 6 km S (5.1
m/s) 74 km 4.5 km
05 Jun (1920) 7.6 km W-SE (7.7
m/s) 222 km 5.1 km
Reference: Luhr, J., Navarro-Ochoa, C., and
Savov, I., (in press), Petrology and mineralogy
of lava and ash erupted from Volcan Colima,
Mexico, during 1999-2005: Special Volume on the
Colima Volcano, from the University of
Guadalajara (edited by Francisco Nunez-Cornu).
Background. The Colima volcanic complex is the
most prominent volcanic center of the western
Mexican Volcanic Belt. It consists of two
southward-younging volcanoes, Nevado de Colima
(the 4,320 m high point of the complex) on the N
and the 3,850-m-high historically active Volcan
de Colima at the S. A group of cinder cones of
probable late-Pleistocene age is located on the
floor of the Colima graben west and east of the
Colima complex. Volcan de Colima (also known as
Volcan Fuego) is a youthful stratovolcano
constructed within a 5-km-wide caldera, breached
to the S, that has been the source of large
debris avalanches. Major slope failures have
occurred repeatedly from both the Nevado and
Colima cones, and have produced a thick apron of
debris-avalanche deposits on three sides of the
complex. Frequent historical eruptions date back
to the 16th century. Occasional major explosive
eruptions (most recently in 1913) have destroyed
the summit and left a deep, steep-sided crater
that was slowly refilled and then overtopped by lava dome growth.
Information Contacts: Observatorio Vulcanologico
de la Universidad de Colima, Colima, Col., 28045,
Mexico (Email: ovc@cgic.ucol.mx); Washington
Volcanic Ash Advisory Center (VAAC), NOAA-NESDES,
Satellite Analysis Branch, 5200 Auth Road, Camp Springs, MD 20746 USA.
Soufriere Hills
Montserrat, West Indies
16.72°N, 62.18°W; summit elev. 915 m
All times are local (= UTC - 4 hours)
Soufriere Hills was last reported on in BGVN
30:03, covering November 2004 to March 2005,
during which time the volcano remained quiet,
with seismic signals, gas emissions and rockfalls
all decreasing. This report, from Montserrat
Volcano Observatory (MVO), covers the period from
late March 2005 to July 2005. The volcano
continued to be relatively quiet through April
and early May, with activity increasing somewhat
through June and several explosive events in late
June and in July. Table 2 summarizes the
seismicity and SO2 emissions during the period of this report.
Table 2. Geophysical and geochemical data
recorded at Soufriere Hills, 25 March 2005 to 15
July 2005. * Only measurement during report
period. **12-hour system failure may have caused
events to be missed. Courtesy of MVO.
Report date Seismicity Number of
earthquakes SO2 flux (metric tons/day)
(2005) level Hybrid VT
LP Rockfalls Range Daily average
25 Mar-01
Apr low 1 5 1 -- 186-369 290
01 Apr-08
Apr low 1 7 1 -- 280-650 400
08 Apr-15
Apr low -- 19 -- -- 261-1877 619
15 Apr-22
Apr -- 7 37 -- 1 122-957 365
22 Apr-29
Apr -- 7 31 -- -- 112-330 304
29 Apr-06
May -- 1 4 -- 1 276-644 439
06 May-13
May -- 1 38 -- 1 221-537 398
13 May-20
May -- 3 18 -- -- 222-363 286
20 May-27
May -- -- 67 -- -- 880* --
27 May-03
Jun -- -- 8** -- -- 167-392 261
03 Jun-10
Jun -- -- 17 -- 1 142-671 399
10 Jun-17
Jun elevated 17 46 20 7 170-750 460
17 Jun-24
Jun elevated 8 4 5 3 430-1150 627
24 Jun-01
Jul elevated 19 15 5 -- 300-700 470
01 Jul-08
Jul elevated 15 9 11 11 241-1700 767
Seismic activity at Soufriere Hills remained at
low levels throughout March and most of April
2005. Beginning on 15 April, vigorous
steam-and-ash venting occurred on the NW side of
Soufriere Hills crater and continued throughout
the period of this report. Average daily SO2
emissions were generally lower than the long-term
eruption average of 500 tons/day, but increased in July to above the average.
On 13 June at 0600 an ash plume reached a height
of ~2.4 km altitude and drifted NE, depositing
light ash in Lookout, Geralds, and St. Peters.
Starting around 10 June, seismic and volcanic
activity were at elevated levels. The ash venting
that began on 13 June declined in intensity
during the following week. The ash venting was
caused by the rapid release of steam and other
volcanic gases, possibly triggered by intense
rainfall on the night of 12 June. Ash analyses
from this episode did not indicate fresh magma.
On 27 June a steam and ash cloud at ~3 km
altitude was reported to be drifting W. By 28
June satellite imagery showed a plume of ash and
steam at ~1.8 km altitude extending NW. Periodic
episodes of intense ash venting continued,
culminating in an explosive event on 28 June at
1306. During the event, ballistics were ejected
onto the Farrell's plain (to the NW), and a
column collapse produced pyroclastic flows. The
pyroclastic flows reached the sea at the Tar
River delta (to the NE), and a smaller volume of
material flowed into the top of Tyre's Ghaut (to
the N). Ash showed no evidence of fresh magma.
Preliminary analysis of recent ground deformation
data from the GPS network at the volcano showed
that deflation during April to mid June 2005 had
later reversed, and the volcano appeared to be
inflating. Periodic ash venting continued and an
explosion occurred on 3 July at 0130, which was
similar to the explosion on 28 June.
An explosive event at 0301 on 18 July caused
widespread ash fallout between Fogarty Hill on
the island's NW and Brodericks Yard on the
island's SW and almost certainly led to
pyroclastic flows to the sea in Tar River. This
explosion was similar to, but slightly bigger
than, the explosion on 3 July, and ash venting
and pyroclastic flows combined to cause dramatic
ash clouds which reached to at least 6 km. Winds
blew the ash plume in a NW direction causing
significant ash fall in Old Towne, Iles Bay,
Salem, Olveston, Woodlands and St Peters. The
maximum depth of ash measured by scientists in
inhabited areas was 1.5 to 2.0 mm; the deepest
ash was recorded at Weekes. Activity subsequently
returned to background levels.
The MVO collected ash samples from the affected
areas to determine whether it was new material
from depth or older material from the dome. Ash
collected after the 28 June and 3 July 2005
events showed no evidence of new magmatic material.
On 28 July 2005, the Moderate Resolution Imaging
Spectroradiometer (MODIS) flying onboard the Aqua
satellite acquired an image of a plume of
volcanic ash drifting westward in a slightly
curving shape as it departs Soufriere Hills (in
the middle of the image, figure 4).
Figure 4. A MODIS image of an ash plume from
Soufriere Hills acquired on 28 July 2005. N is
towards the top. The plume was visible for over
100 km, but conspicuous portions of the plume
continued beyond the W (left) side of this image
between the arrows. A Washington VAAC report from
that day suggested a plume to ~ 5 km altitude and
70-300 km long, blown W. Several islands
neighboring Montserrat (M) are labeled: A,
Antigua; B, Barbuda; G, Guadeloupe; N, Nevis; and
SK, St. Kitts. For scale, the distance between
the centers of the islands of Montserrat and
Antigua is ~ 55 km. Some islands are ringed in
bright blue-green, the possible result of coral
reefs in shallow water, sediment, phytoplankton,
or some combination of these conditions. Image
and some elements of the caption courtesy of Jeff
Schmaltz, MODIS Rapid Response Team, NASA.
Background. The complex andesitic Soufriere Hills
volcano occupies the southern half of the island
of Montserrat. The summit area consists primarily
of a series of lava domes emplaced along an
ESE-trending zone. Prior to 1995, the youngest
dome was Castle Peak, which was located in
English's Crater, a 1-km-wide crater breached
widely to the E. Block-and-ash flow and surge
deposits associated with dome growth predominate
in flank deposits. Non-eruptive seismic swarms
occurred at 30-year intervals in the 20th
century, but with the exception of a 17th-century
eruption, no historical eruptions were recorded
on Montserrat until 1995. Long-term
small-to-moderate ash eruptions beginning in that
year were later accompanied by lava dome growth
and pyroclastic flows that forced evacuation of
the southern half of the island and ultimately
destroyed the capital city of Plymouth, causing
major social and economic disruption to the island.
Information Contact: Montserrat Volcano
Observatory (MVO), Fleming, Montserrat, West Indies (URL: www.mvo.ms/).
St. Helens
Washington, USA
46.20°N, 122.18°W; summit elev. 2,549 m
All times are local (= UTC - 8 hours)
Throughout the period covered by this report,
March 2005 to July 2005, growth of the new lava
dome inside the crater of St. Helens continued,
accompanied by low rates of both seismicity and
gas and ash emissions. The hazard status remained
at 'Volcano Advisory' (Alert Level 2); aviation
color code Orange. Results from a digital
elevation model produced from imagery taken on 21
February showed the highest part of the new lava
dome was 12 m higher than on 1 February; during
that 3 week period the volume of dome and
surrounding uplift had increased by 3 million
cubic meters. The average rate of growth
continued at ~2 m^3/s. Figure 5 shows four views
of changes to the lava dome during the period of
this report. Figure 6 shows the seismicity and
the time of the larger recognized explosions.
Figure 5. Four views into St. Helens's crater
from different perspectives and dates, focusing
on the new dome. A: 15 March 2005, view from NE.
The whaleback is close to its maximum length of
500 m. Note that the glacier's heavily crevassed,
half-moon shaped, E (left) arm lies squeezed
between the growing dome and crater wall. Vent is
steaming at lower-right whaleback. B: 3 May 2005,
view from N. The whaleback has been breaking
apart for several weeks. Note the large slab of
smooth gouge-covered surface moving E (left). C:
21 June 2005, view from NW. Note the development
of broad talus on W (right) flank of dome. An
isolated body of smooth gouge-covered surface to
the right of the main spine is emerging from
talus. D: 26 July 2005, view from E crater rim.
The smooth, gouge-covered spine continues to
crumble as a result of M$ 3 earthquakes and
rockfalls. A large slab of March whaleback is
visible at left. Most of the dome surface is now
talus and disintegrating older whalebacks. By the
end of July, the spine had been reduced to a
highly fractured stump. All photos courtesy of USGS CVO.
Figure 6. Magnitude of located earthquakes at
Mount St. Helens through 27 July 2005 (Pacific
Northwest Seismograph Network). Vertical lines
represent the time of moderate explosions. Note
periods of earthquakes M > 3 that accompanied
dome break-ups in December, April, and July.
Courtesy of CVO and the Pacific Northwest Seismograph Network.
During 2-7 March, dome growth accompanied low
rates of both seismicity and gas and ash
emissions. Parts of the growing lava dome
continued to crumble, forming rockfalls and
generating small ash clouds that drifted out of
the crater. The bulging ice on the deformed E arm
of the glacier in the crater continued to move
rapidly N at about 1.2 m per day (figure 7).
Figure 7. A view of the growing dome at St.
Helens from the Sugar Bowl camera just before the
8 March 2005 explosion. The Sugar Bowl digital
camera takes a picture every hour from its
housing on the NE flanks. The image data are
transmitted to a more accessible spot immediately
after the pictures are taken. Courtesy of CVO.
A small explosive event began at approximately
1725 on 8 March. The eruption lasted about 30
minutes with intensity gradually declining
throughout; a fine dusting of ash from this event
later fell ~100 km to NW (in Yakima, and
Toppenish, Washington). By 0200 on 9 March, the
leading edge of the faint, diffuse plume had
reached ~300 km to the E (over western Montana).
After the explosion scientists found the lava
dome intact. They recognized ballistics (up to ~1
m in diameter) as far as the N flank of the old
lava dome and a lack of them along or beyond the
crater rim. The explosion vented from the NNW
side of the new lava dome, very near the source
of the 1 October 2004 and 16 January 2005 explosions (figure 8).
Figure 8. The 8 March 2005 explosion at St.
Helens viewed from the Sugar Bowl camera. This
shot was taken at about 1727 hours and 42 seconds on 8 March. Courtesy of CVO.
The explosion on 8 March was one of the largest
steam-and-ash emissions to occur since renewed
activity began in October 2004. The Cascades
Volcano Observatory (CVO) lost radio signals from
three monitoring stations in the crater soon
after the event started. The event followed a few
hours of slightly increased seismicity not then
interpreted as precursory. There were no other
indications of an imminent change in activity.
After the 8 March explosion, St. Helens only
emitted steam, and seismicity dropped to a level
similar to that during the several hours prior to
the explosion. Gas emissions were very low,
essentially unchanged from those measured in late
February. The hazard status for the ongoing
eruption, 'Volcano Advisory (Alert Level 2),'
mentioned the possibility of events like the 8
March explosion occurring without warning. That
assessment remained unchanged and the hazard status stayed the same.
Analysis of aerial photographs indicated that as
of 10 March the topographic changes in the crater
resulting from growth of the new dome and
consequent glacier deformation had a combined
volume of about 45 million m^3. The current
eruption contributed new materials amounting to
about two-thirds the volume of the old lava dome.
From March 2005 through July 2005, growth of the
new lava dome continued. Rates remained low for
both seismicity and gas and ash emissions. CVO
noted that during such eruptions, episodic
changes in the level of activity can occur over
days to months. During about 26-27 March, a group
of M 2 to M 3 earthquakes occurred beneath the
volcano, a level of activity considered normal during dome-emplacing volcanism.
A series of large (M >=3) earthquakes occurred
during 3-4 April, in addition to the typical
array of smaller events. Observations on 6 April
revealed that the smooth whaleback-shaped portion
of the growing lava dome was broken by numerous
fractures, and the edges had crumbled greatly.
Several deep gashes on the E, N, and W sides
frequently produced rockfalls and accompanying
ash clouds. On 10 April the new dome continued to
fracture and spread laterally. As a consequence,
the dome's summit dropped by a few tens of meters
over 2-3 weeks, leaving isolated high-standing
remnants. This broken pattern was apparent in a
photograph on 3 May (figure 5B).
Earthquakes steadily decreased in magnitude and
number through mid-April. A GPS receiver 200 m N
of the new dome crept steadily NNW at ~10 cm per
day. The combination of the GPS measurements
adjacent to the lava dome and the qualitative
estimate of lateral spreading suggested that
extrusion of new lava continued during April.
On the morning of 28 April there were reports of
minor amounts of ashfall in the eastern part of
the Portland metropolitan area, ~80 km SSW of St.
Helens. There was no evidence of a new explosion.
CVO scientists determined that large convective
storms over the Cascades on 27 April entrained
ash generated by the frequent hot rockfalls from
the growing lava dome and kept it in suspension
to fall out as far away as Portland.
During early May poor weather obscured the
volcano. Seismic and ground deformation activity
remained unchanged. Through much of the night of
4-5 May, however, VolcanoCam images detected
intermittent glow from the new dome. The camera
is mounted at the Johnston Ridge Observatory at
an elevation of 1,400 m and ~6.5 km NNW of the
volcano, a spot W of the S part of Spirit Lake.
During 11-12 May images from the mouth of the
crater showed the new spine of lava at the N end
of the dome continuing to grow. Data from seismic
and GPS instruments in the crater and on the
outer flanks continued to lack significant
changes over the past few weeks. Through the end
of May, lava extrusion continued at the N end of
the new lava dome, while the high spines
continued to crumble. Other parts of the lava
dome moved at the relatively low velocity of
about 30 cm/day or remained stagnant. Table 3
compares the older dome with the new one as of 3 May 2005.
Table 3. A comparison of the old (1980-86) and
new (2004-) domes at St. Helens. The new dome
started in October 2004, and the reported data
reflects conditions seen until 1 February 2005. Courtesy of CVO.
Names Unnamed (the "old" dome) The "new" dome
(unofficially
called "the whaleback")
Growth period 1980-1986 (six
years) October 2004-February 2005 (and ongoing)
Size - length ~ 1.1 km in diameter ~ 475 m long
Size - width ~ 1.1 km in diameter ~ 152 m wide
Elevation / 2.2 km, nearly 267
m As of 1 February 2005, 2.3 km, nearly 415 m
vertical height above the 1980
crater above the 1980 crater floor, 152 m above the top
floor.
of the old 1980-86 lava dome, and 213 m above
the
2000 glacier surface. The new dome's top
reached
an elevation ~ 40 m below Shoestring
Notch on the crater's SE rim.
Volume ~ 75 x 10^6 m3 ~ 44 x 10^6 m3
Around 4 June the rate of motion of a GPS unit on
the NE part of the new dome slowed slightly,
continuing to creep eastward and northward at a
rate of several centimeters per day, but no
longer rising vertically. The lava spine,
however, continued to grow. Through the end of
June 2005, seismic and deformation data continued
trends similar to the previous few weeks, with
small earthquakes approximately every 5 minutes,
little to no movement of the old lava dome, minor
movement of the N end of the new lava dome, and
continued growth of the lava spine. Observations
made on 15 June revealed that the lava spine
continued to grow and that temperatures in cracks
near the base of the spine were near 700°C.
Thermal data from 15 June suggested that much of
the W part of the dome was moving upward, as well
as southward. During the last week of June, the
smooth lava spine continued to grow at a rate of
about 1.8-3.7 m per day. Rockfalls from the top
of the spine kept its height from increasing by
that same rate. Analysis of a digital elevation
model made from imagery acquired on 15 June
showed that the total volume addition to the
crater since September 2004 had reached almost 60 million cubic meters.
On 2 July at 0630 a rockfall from the growing
lava dome removed a large piece of the dome's
top, producing an ash plume that rose above the
crater rim and generating a substantial seismic
signal. Persistent smaller rockfalls from the
growing lava dome built talus aprons on the W and NE flanks of the dome.
On 12 July, CVO reported that rates of seismicity
and ground deformation at Mount St. Helens had
declined during the previous two weeks to some of
the lowest levels since the eruption began in
September 2004. A similar lull occurred in December 2004.
Beginning 15 July and continuing through the end
of the month, the growing spine and other high
areas of the dome to the south produced numerous
large rockfalls, most of which were associated
with earthquakes of about M 3 (figure 9). Diffuse
ash plumes that rose hundreds of meters above the
rim were produced by the larger rockfalls. By the
end of July most of the smooth gouge-covered
surface of the spine had disintegrated, and the
spine was reduced to a highly fractured, but
still-extruding, stump surrounded by rapidly growing aprons of rockfall debris.
Figure 9. Rockfall and accompanying ash cloud on
26 July 2005 as viewed from station Brutus on the
crater's E rim. Rockfall originated from the
steep, fractured top of an inclined spine. Note
boulders (light-colored specks against shadow)
shooting ahead of ash cloud. Another spine is
extruding from ground just behind the lower end
of the ash cloud. Courtesy USGS and CVO.
Background. Prior to 1980, Mount St. Helens
formed a conical, youthful volcano sometimes
known as the Fuji-san of America. During the 1980
eruption the upper 400 m of the summit was
removed by slope failure, leaving a 2 x 3.5 km
horseshoe-shaped crater now partially filled by a
lava dome. Mount St. Helens was formed during
nine eruptive periods beginning about 40-50,000
years ago and has been the most active volcano in
the Cascade Range during the Holocene. Prior to
2200 years ago, tephra, lava domes, and
pyroclastic flows were erupted, forming the older
St. Helens edifice, but few lava flows extended
beyond the base of the volcano. The modern
edifice was constructed during the last 2200
years, when the volcano produced basaltic as well
as andesitic and dacitic products from summit and
flank vents. Historical eruptions in the 19th
century originated from the Goat Rocks area on
the N flank, and were witnessed by early settlers.
Information Contacts: Cascades Volcano
Observatory (CVO), U.S. Geological Survey, 1300
SE Cardinal Court, Building 10, Suite 100,
Vancouver, WA 98683-9589, USA (URL:
vulcan.wr.usgs.gov/; Email:
GSCVOWEB@usgs.gov); Pacific Northwest Seismograph
Network (PNSN), Seismology Lab, University of
Washington, Department of Earth and Space
Sciences, Box 351310, Seattle, WA 98195-1310, USA
(URL: www.pnsn.org/; Email: seis_info@ess.washington.edu).
Ebeko
Kurile Islands, Russia
50.68°N, 156.02°E; summit elev. 1,156 m
All times are local (= UTC +11 hours)
A few gas-and-steam plumes from Ebeko were
reported during February-April 2004 (BGVN 29:04).
The most recent previous eruption was in January
1991. On 30 January 2005 the Kamchatka Volcanic
Eruptions Response Team (KVERT) raised the
Concern Color Code at Ebeko from Green to Yellow
after reports of a strong smell of sulfur on 27
and 28 January in the town of Severo-Kurilsk, ~7 km from Ebeko.
Observations by Leonid and Tatiana Kotenko in
Severo-Kurilsk during May-July 2004 included
occasional gas-and-steam plume rising as high as
250 m above the volcano during clear weather and
fumarolic plumes moving close to the ground.
There was no visible activity in August, but a
few plumes were seen again from September to November.
During 28 January, a white gas-and-steam plume
was seen from Severo-Kurilsk rising 400 m above
the volcano. Summit observations the next day
revealed a yellow-gray, 5-m-diameter, column
rising 300 m from a vent on the NE side of the
active crater. Three ash layers 2-3 mm thick were
noted 10 m from the vent, and ash extended ~500 m
E into the crater. At this time a new 7 x 12 m
turquoise lake had developed in the SW part of
the active crater. The lake disappeared on 30
January, and there was intensive fumarolic
activity where it had been. Shallow earthquakes
were recorded at the Severo-Kurilsk seismic station.
On 1 February gas-and-steam plumes rose to 450 m
above Ebeko's crater and drifted NE. On 7
February a small emission of steam, gas, and
possibly ash rose ~1 km above the crater and
drifted ~12 km SE. On 8 and 9 February plumes
rose to 600 m and thin ash deposits were noted in the town of Severo-Kurilsk.
The following information came to KVERT from
observers in Severo-Kurilsk (Leonid and Tatiana
Kotenko). On 15-16 February a dark-gray column
rose up to 500 m above the crater. A dark-gray
plume extended 6 km E and a light-gray plume 7 km
SE. On 16 February ashfall together with snowfall
was noted over the strait to the E of Paramushir
Island. On 17 February a white column up to 250 m
above the crater was observed. On 12 February and
16-17 February a strong smell of a H2S was noted
at Severo-Kurilsk. On 18-19 February white
gas-and-steam columns 5 m in diameter rose from
the two vents up to 450 m above the crater and a
new lake (10 x 10 m) on the floor of the active
crater was observed. On 25 February white
gas-and-steam plumes rose to 450 m and 1,000 m
above the crater. Gas-and-steam plumes were also
observed on 1-2, 4-5, and 9 March. No ash was
seen. A strong smell of H2S was noted at
Severo-Kurilsk on 25 February and 2 March.
About 20 seismic events of less than Ml 2.0 were
observed during 1-9 March at the Severo-Kurilsk
seismic station. No seismic activity was observed
from 12 to 14 March. On 15 March two seismic
events were noted. There was no seismicity during
18-25 March, so KVERT reduced the hazard status
from Yellow to Green, the lowest level.
The Russian Emergency Situations Ministry's
Sakhalin department reported renewed activity on
27 June in the form of emission clouds rising to
a maximum height of 200 m above the crater and
drifting SW. KVERT did not report any activity,
and the Concern Color Code for Ebeko remained at Green.
Background. The flat-topped summit of the central
cone of Ebeko volcano, one of the most active in
the Kuril Islands, occupies the northern end of
Paramushir Island. Three summit craters located
along a SSW-NNE line form Ebeko volcano proper,
at the northern end of a complex of five volcanic
cones. Blocky lava flows extend W from Ebeko and
SE from the neighboring Nezametnyi cone. The
eastern part of the southern crater of Ebeko
contains strong solfataras and a large boiling
spring. The central crater of Ebeko is filled by
a lake about 20 m deep whose shores are lined
with steaming solfataras; the northern crater
lies across a narrow, low barrier from the
central crater and contains a small, cold
crescent-shaped lake. Historical activity,
recorded since the late-18th century, has been
restricted to small-to-moderate explosive
eruptions from the summit craters. Intense
fumarolic activity occurs in the summit craters
of Ebeko, on the outer flanks of the cone, and in lateral explosion craters.
Information Contacts: Olga Girina, Kamchatka
Volcanic Eruptions Response Team (KVERT), a
cooperative program of the Institute of Volcanic
Geology and Geochemistry, Far East Division,
Russian Academy of Sciences, Piip Ave. 9,
Petropavlovsk-Kamchatskii 683006, Russia (Email:
girina@kcs.iks.ru); Alaska Volcano Observatory
(AVO), cooperative program of the U.S. Geological
Survey, 4200 University Drive, Anchorage, AK
99508-4667, USA (URL: www.avo.alaska.edu/;
Email: tlmurray@usgs.gov), the Geophysical
Institute, University of Alaska, P.O. Box 757320,
Fairbanks, AK 99775-7320, USA (Email:
eisch@dino.gi.alaska.edu), and the Alaska
Division of Geological and Geophysical Surveys,
794 University Ave., Suite 200, Fairbanks, AK
99709, USA (Email: cnye@giseis.alaska.edu).
Shiveluch
Kamchatka, Russia
56.653°N, 161.360°E; summit elev. 3,283 m
All times are local (= UTC + 12 hours [+ 13 hours in March-June])
Following explosions from Shiveluch during 25
February to 4 March 2005 ash fell in
Ust'-Hairyuzovo, about 250 km W (BGVN 30:02).
From March 2005 until July 2005, Shiveluch
remained at Concern Color Code Orange. Throughout
March 2005 the lava dome at Shiveluch continued
to grow and on several days ash-and-gas plumes
and gas-and-steam plumes rose to a maximum of
~2.8 km above the dome. Satellite imagery showed
a thermal anomaly at the dome during the first
week of March and a large thermal anomaly over
the recent pyroclastic-flow deposit during 11-12
March. Between 5-28 March a new lava extrusion
added ~50 m height to the SW part of the dome.
During April 2005, intensive growth of the new
extrusion at the W part of the dome continued,
and the E and W parts of the lava dome became
nearly level. Gas-and-steam plumes rose to a
maximum of ~1.2 km above the dome during April
2005. Satellite imagery showed a large thermal
anomaly at the dome during mid-April and a small
anomaly associated with a pyroclastic flow on 19
April. On 25 April, a hot avalanche on the dome's
W side produced an ash plume that rose ~2 km
above the 2.5-km-high lava dome. Growth of the
dome continued during May 2005 with a new
extrusion to the W. Ash-and-gas plumes, some
rising 2 km above the dome, were frequent.
Satellite imagery showed a persistent thermal
anomaly at the lava dome throughout May.
The dome continued to grow during June 2005.
During 3-10 June, two shallow M 1.6-1.7
earthquakes occurred 0-5 km beneath the active
dome. Gas-and-steam plumes rose as high as 400 m
above the dome during June. A persistent thermal
anomaly was visible throughout June. Fumarolic
activity was reported during the week of 18-24
June. During the last week of June, satellite
imagery showed a persistent thermal anomaly, and
fumarolic activity produced steam to 4-5 km
altitude. On 30 June, ash-and-gas plumes rose 3-5
km altitude. and drifted NW. Hot avalanches of
volcanic material were also recorded. On 6 July
ash-and-gas plumes rose to ~7 km altitude and
drifted NW. On 7 July an 11-minute-long seismic
event occurred, and ash-and-gas plumes may have
reached a height of 10 km altitude. Around 8
July, KVERT raised the Concern Color Code from
Orange to Red, the highest level. On 8 July 2005,
video footage showed weak gas-and-steam plumes
rising to ~5 km altitude. On 9 July 2005, the
Concern Color Code was reduced to Orange.
Background. The high, isolated massif of
Shiveluch volcano (also spelled Sheveluch) rises
above the lowlands NNE of the Kliuchevskaya
volcano group. The 1300 cu km Shiveluch is one of
Kamchatka's largest and most active volcanic
structures. The summit of roughly 65,000-year-old
Strary Shiveluch is truncated by a broad
9-km-wide late-Pleistocene caldera breached to
the south. Many lava domes dot its outer flanks.
The Molodoy Shiveluch lava dome complex was
constructed during the Holocene within the large
horseshoe-shaped caldera; Holocene lava dome
extrusion also took place on the flanks of Strary
Shiveluch. At least 60 large eruptions of
Shiveluch have occurred during the Holocene,
making it the most vigorous andesitic volcano of
the Kuril-Kamchatka arc. Widespread tephra layers
from these eruptions have provided valuable time
markers for dating volcanic events in Kamchatka.
Frequent collapses of dome complexes, most
recently in 1964, have produced debris avalanches
whose deposits cover much of the floor of the breached caldera.
Information Contacts: Olga A. Girina, Kamchatka
Volcanic Eruptions Response Team (KVERT), a
cooperative program of the Institute of Volcanic
Geology and Geochemistry, Far East Division,
Russian Academy of Sciences, Piip Ave. 9,
Petropavlovsk-Kamchatskii 683006, Russia (Email:
girina@kcs.iks.ru), the Kamchatka Experimental
and Methodical Seismological Department (KEMSD),
GS RAS (Russia), and the Alaska Volcano
Observatory (USA); Alaska Volcano Observatory
(AVO), a cooperative program of the U.S.
Geological Survey, 4200 University Drive,
Anchorage, AK 99508-4667, USA (URL:
www.avo.alaska.edu/; Email:
tlmurray@usgs.gov), the Geophysical Institute,
University of Alaska, P.O. Box 757320, Fairbanks,
AK 99775-7320, USA (Email:
eisch@dino.gi.alaska.edu), and the Alaska
Division of Geological and Geophysical Surveys,
794 University Ave., Suite 200, Fairbanks, AK
99709, USA (Email: cnye@giseis.alaska.edu).
Karymsky
Kamchatka, Russia
54.05°N, 159.43°E; summit elev. 1,536 m
All times are local (= UTC + 12 hours)
During 1 January to mid-April 2004 (BGVN 29:04),
ash-and-gas explosions and gas plumes were
observed and seismicity remained generally above
background levels. From May to the beginning of
September 2004, seismic activity remained above
background levels, varying over this time from
100-800 small shallow earthquakes per day.
Ash-and-gas explosions and gas plumes to a
maximum height of 7.5 km were frequent. On 1
September 2004 an increase in activity led the
Kamchatka Volcanic Eruptions Response Team
(KVERT) to raise the Concern Color Code from
Yellow to Orange. From September to December
2004, seismicity remained above background
levels, and ash-and-gas explosions and ash plumes
were frequent. On 12 November the hazard status was lowered to Yellow.
Increasing seismicity, rock avalanches and
possible ash plumes to 2.5 km altitude led KVERT
to raise the Concern Color Code to Orange again
on 7 December 2004. On 28 December, an observed
eruption at Karymsky produced a plume composed
primarily of gas and steam, but with some ash,
that rose to ~1 km above the crater. Thermal
anomalies were also visible on satellite imagery
on 27 and 28 December. On 30 December the Tokyo
VAAC reported that a plume was present up to ~8 km altitude extending SW.
There were no seismic data from 12 December 2004
till late January 2005. Through January and
February thermal anomalies were frequently
visible on satellite imagery. Seismicity remained
above background levels from February 2005 through July 2005.
Through March and April 2005, ash-and-gas
explosions and gas plumes were frequent. Ash
deposits extended 10-15 km S and SW of the
volcano. On 20 April, volcanic bombs rose to 50 m
above the crater, and ash fell to the NE on 21
April. On 26 and 27 April, Strombolian activity
was seen in two of the volcano's craters;
volcanic bombs rose to ~300 m above the craters.
Ash fell to the SE on 22-23 April and
pyroclastic-flow deposits were seen on the NNW
flank of the volcano. During May 2005,
ash-and-gas explosions and plumes were again
frequent, and a thermal anomaly continued to be visible on satellite imagery.
Due to a decrease in seismic and volcanic
activity during 3-10 June, KVERT decreased the
alert level from Orange to Yellow. Seismic
activity increased starting on 22 June. Ash
explosions up to 3,000 m altitude traveling SW
were observed by pilots. According to seismic
data, about 10 ash-and-gas plumes and avalanches
occurred at the volcano. On 23 June KVERT
increased the alert level to Orange. Satellite
imagery of Karymsky showed a narrow ash-and-gas
plume at a height of ~3.5 km altitude on 30 June.
Based on interpretations of seismic data,
ash-and-gas plumes may have reached 3 km above the crater.
The Tokyo VAAC posted four messages on Karymsky
during the 90 days prior to 8 August 2005; in
each, ash was not identifiable from satellite.
The earliest, 18 May was similar to the last one,
on 23 June. Both noted a reported plume to FL100
('flight level 100' signifies 10,000 feet; 3.05
km altitude). Reports on 22 and 24 May both noted
ash to FL 120 (3.65 km altitude).
Background. Karymsky, the most active volcano of
Kamchatka's eastern volcanic zone, is a
symmetrical stratovolcano constructed within a
5-km-wide caldera that formed during the early
Holocene. The caldera cuts the south side of the
Pleistocene Dvor volcano and is located outside
the north margin of the large mid-Pleistocene
Polovinka caldera, which contains the smaller
Akademia Nauk and Odnoboky calderas. Most
seismicity preceding Karymsky eruptions
originated beneath Akademia Nauk caldera, which
is located immediately S of Karymsky volcano. The
caldera enclosing Karymsky volcano formed about
7600-7700 radiocarbon years ago; construction of
the Karymsky stratovolcano began about 2000 years
later. The latest eruptive period began about 500
years ago, following a 2300-year quiescence. Much
of the cone is mantled by lava flows less than
200 years old. Historical eruptions have been
vulcanian or vulcanian-strombolian with moderate
explosive activity and occasional lava flows from the summit crater.
Information Contacts: KVERT (see Shiveluch);
Tokyo Volcanic Ash Advisory Center (VAAC), Japan
Meteorological Agency, Tokyo Aviation Weather
Service Center, Haneda Airport 3-3-1, Ota-ku,
Tokyo 144-0041, Japan (URL:
www.jma.go.jp/JMA_HP/jma/...enter/vaac/;
Email: vaac@eqvol.kishou.go.jp).
Canlaon
central Philippines
10.412°N, 123.132°E; summit elev. 2,435 m
All times are local (= UTC + 8 hours)
Throughout May 2005, PHIVOLCS noted that
ash-and-steam emissions from Canlaon produced
plumes to 500-1,000 m above the volcano. The
hazard status remained at Alert Level 1. The SO2
flux remained above the 'normal' level of 500
metric tons/day (t/d) with values of 2,700 t/d on
1 May, 2,080 on 22 May, and 1,400 on 26 May.
According to news reports, flights to and from
nearby Kalibo airport were suspended on 3 May due to reduced visibility.
Although voluminous white steam continued to be
discharged from the active vent early in June
2005, after 25 May ash ejections stopped and ash
contents in the steam plume were significantly
reduced. On 3 June PHIVOLCS lowered the hazard
status of Canlaon from Alert Level 1 to Alert
Level Zero, listing a variety of reasons. For
one, they noted the downtrend in the SO2 gas
emission rate from a high of about 4,900 t/d, to
the prevailing level of 1,500 t/d. For another,
they noted the absence of significant seismic
activity before, during, and after the ash
emissions. And finally, they cited a lack of
significant observations indicating near-surface
hydrothermal activity. Since Canlaon has a
history of sudden outbursts, the public was
reminded to refrain from entering the 4-km-radius
Permanent Danger Zone (PDZ) and to coordinate
with PHIVOLCS and Disaster Management Councils in
any attempt to climb the volcano.
Background. Canlaon volcano (also spelled
Kanlaon), the most active of the central
Philippines, forms the highest point on the
island of Negros. The massive 2435-m-high
stratovolcano is dotted with fissure-controlled
pyroclastic cones and craters, many of which are
filled by lakes. The summit of Canlaon contains a
broad elongated northern caldera with a crater
lake and a smaller, but higher, historically
active crater to the south. The largest debris
avalanche known in the Philippines traveled 33 km
to the SW from Canlaon. Historical eruptions,
recorded since 1866, have typically consisted of
phreatic explosions of small-to-moderate size
that produce minor ashfalls near the volcano.
Information Contacts: Philippine Institute of
Volcanology and Seismology (PHIVOLCS), Department
of Science and Technology, PHIVOLCS Building,
C.P. Garcia Avenue, Univ. of the Philippines
Campus, Diliman, Quezon City, Philippines (URL:
www.phivolcs.dost.gov.ph/); Chris Newhall,
USGS, Box 351310, University of Washington,
Seattle, WA 98195-1310, USA(Email:
cnewhall@ess.washington.edu); Philippine Star (URL: www.philstar.com/).
Kilauea
Hawaiian Islands, USA
19.425°N, 155.292°W; summit elev. 1,222 m
All times are local (= UTC - 10 hours)
Activity at Kilauea through October 2004 was
previously reviewed in reports that included maps
showing the extent of key lava flows through most
of August 2004 (BGVN 29:09). During November 2004
through January 2005, lava flows were abundant
and made complex patterns. Their overall advance
can be seen by comparing maps of the extent of
the lava flows as of late August 2004 (figure 10)
and 2 February 2005 (figure 11).
Figure 10. Kilauea lava flows erupted during
activity from 1983-August 2004 of Pu`u `O`o and
Kupaianaha. Note the location of Kupaianaha, the
active vent area during 1986-1992, ~ 4 km ENE of
Pu`u `O`o. Courtesy of the U.S. Geological
Survey's Hawaiian Volcano Observatory.
Figure 11. Kilauea lava flows erupted during
activity from 1983-2 February 2005 of Pu`u `O`o
and Kupaianaha. Courtesy of the U.S. Geological
Survey's Hawaiian Volcano Observatory.
On 4 November 2004 lava from the Prince Kuhio
Kalaniana `ole (PKK) flow entered the sea,
forming a new delta seaward of the E end of the
old Lae'apuki delta. The PKK flow has been
continuously active since 26 July 2004, and lava
continued to enter the sea through 26 November
2004. This was the first time lava entered the
sea since the Banana lava flow ceased in early
August 2004. The Banana flow developed from
breakouts when lava escaped from the confines of
the Mother's Day lava tube, emerging near the
former Banana Tree kipuka. This flow stagnated
early in September 2004, and the Mother's Day
tube ceased carrying lava late in 2004.
During the first week in December 2004, the lava
flow at Lae'apuki abated. Activity resumed during
the second week along all areas of the PKK flow
from high on the Pulama pali fault scarp. By 13
December lava again entered the sea at the East
Lae'apuki delta. The flow moderated during the
second half of December with only several areas
of visible surface lava apparent on the Pulama
pali fault scarp and on the coast.
New vents opened at the southern base of Pu`u
`O`o on 19 January 2004 and fed the Martin Luther
King (MLK) flows (figure 11). The PKK flow
originated from two vents ~250 m S of the base of
Pu `u `O`o. By 2 February 2005 the PKK flow had
entered the sea at West Highcastle, Lae'apuki, and Ka`ili`ili (figure 11).
During January 2005, surface lava was visible
along the three main arms of the PKK flow as they
advanced downslope towards the coast (figure11).
The middle arm of the PKK flow was comparatively
small, and it failed to reach the ocean during
this reporting interval; it remained high on
Pulama pali. In contrast, lava from the E and W
arms of the PKK flow began to enter the ocean on
31 January. The large E arm of the PKK lava flow
fed the larger Ka`ili`ili entry. The W branch of
the PKK lava flow once supplied lava to Lae'apuki
(an E branch of the W arm), but later also began
feeding the West Highcastle ocean entry (the W branch of the W arm, figure 11).
Seismicity. After seven months of relative
quiescence renewed seismicity and numerous small
long-period (LP) events again became visible in
November 2004 on the North Pit seismogram.
Elevated activity began on 16 November, peaking
at over 2,000 events a day by late November
(figure 12). Nearly all of these earthquakes were
too small to catalog. To obtain this plot, a
daily event count was extrapolated from a
representative part of the North Pit (NPT)
seismogram. Scientists combined the counts for
two shallow (0-5 km deep) earthquake types, those
designated by HVO as short-period summit or
short-period caldera (SPC) and those designated
as shallow, long-period (long-period caldera A,
LPC-A) earthquakes. The similar frequency content
of these two kinds of earthquakes make them
difficult to distinguish on the drum record. In
addition, small-magnitude deeper earthquakes,
designated as long-period earthquakes originating
at depths over 5 km, may have also registered
within the summit caldera to appear on the plot,
although they would be expected to contain a
lower dominant frequency of oscillation than the
LPC-A earthquakes. Tremor episodes were rare or absent.
Figure 12. A time series of Kilauea's daily
earthquakes (SPC, LPC-A, and possibly LPC-C
types) registered at the summit during October
2004 through January 2005. Courtesy of U.S.
Geological Survey's Hawaiian Volcano Observatory.
A minor peak in seismicity occurred in later
January, during the two days before and after the
25 January inflation-deflation event. Most of the
events on 25 January appeared to be of the SPC variety.
Tilt and deformation. The tiltmeter record at
Kilauea summit (UWE) and Pu`u `O`o (POC) showed
numerous correlated tilt changes, with a short
time delay between UWE and POC stations and
larger magnitude delays at POC (figure 13). One
of the largest of these deformations took place
on 25-26 November and resulted in about 3
microradians of tilt at UWE, and 5 microradians
at POC. This was similar in character to the tilt
events of recent months, starting with fairly
rapid deflation, followed by a similar rate and
magnitude of inflation. Though they differ in
character from the deflation-inflation-deflation
(DID) cycles of the past few years, they seem to
be originating from the same shallow storage area
near Halemaumau, the crater at Kilauea's summit.
Figure 13. Electronic tiltmeter records from the
N flank of Pu`u `O`o cone (POC) and NW rim of
Kilauea caldera (UWE) for (A) October and
November 2004 and (B) December 2004 through
January 2005. Only the radial component is
plotted, i.e., the direction that maximizes
signal from the most common sources of tilt at
both locations. Courtesy of U.S. Geological
Survey's Hawaiian Volcano Observatory.
Kilauea continued to inflate over this reporting
period. The extension rate across the summit
increased dramatically in early January 2005,
from an average rate of about 8 cm/yr to over 40
cm/yr. There was a short inflation-deflation
event on 25 January, followed by about 2-3 days
of extremely rapid movement of the S flank;
continuous GPS stations on the S coast were
displaced by up to 2 cm. The pattern and rate of
motion are very similar to the slow earthquake of
November 2000. The slip event occurred during a
swarm of earthquakes (see seismic section
above), but the cumulative magnitude of these
earthquakes was not nearly as great as the
estimated equivalent moment magnitude of the slip.
Other large episodes of correlated multistation
tilt occurred on 14 December 2004 and 25 January
2005. In December, both UWE and POC recorded
deflationary tilts of about 4 and 2.5
microradians, respectively, over about 12 hours.
In mid-January, the summit started showing a high
rate of inflationary tilt, coinciding with the
increase in cross-summit extension, measured by
continuously recording GPS. In the early morning
of 25 January, summit tiltmeters and POC recorded
a rapid inflation (about 5.5 microradians in an
hour at UWE, 2 at POC) followed by an equal
amount of deflation over the next day. The event
was similar to the fairly frequent
deflation-inflation-deflation (DID) events at
Kilauea. Similarities included the apparent
source regions of the inflation, the seismic
signature, the delay time between the summit and
the rift zone, and the timing of increased activity.
SO2 emission rate measurements. Summit SO2
emission rates for October/November ranged from
80 to 130 metric tons per day (t/d) with an
average of 105 t/d (standard deviation, s.d.=20
t/d for 36 measurements made over 6 days).
Although this represents a slight decrease over
emission rates measured during the previous
reporting period, it does not represent a
significant change. Correlation spectrometer
(COSPEC) SO2 measurements along the Chain of
Craters Road yielded SO2 flux rates of
1,080-1,660 t/d with a mean value of 1,270 t/d
(s.d. of 260 t/d for 27 measurements made over 4
days). The drop in emissions, which began in May
2004, had continued through November 2004. A lack
of trade winds hindered SO2 flux measurements
during November and December. Six traverses on 6
December yielded an emission rate of 105 t/d
(s.d.=10 t/d) consistent with the more frequent
measurements made during September-October 2004.
The return of the tradewinds in early February
allowed measurements to resume and showed that
summit emissions had decreased markedly, likely
due to the heavy rainfall on 4 February.
Background. Kilauea volcano, which overlaps the E
flank of the massive Mauna Loa shield volcano,
has been Hawaii's most active volcano during
historical time. Eruptions of Kilauea are
prominent in Polynesian legends; written
documentation extending back to only 1820 records
frequent summit and flank lava flow eruptions
that were interspersed with periods of long-term
lava lake activity that lasted until 1924 at
Halemaumau crater, within the summit caldera. The
3 x 5 km caldera was formed in several stages
about 1500 years ago and during the 18th century;
eruptions have also originated from the lengthy
East and SW rift zones, which extend to the sea
on both sides of the volcano. About 90% of the
surface of the basaltic shield volcano is formed
of lava flows less than about 1,100 years old;
70% of the volcano's surface is younger than 600
years. A long-term eruption from the East rift
zone that began in 1983 has produced lava flows
covering more than 100 km^2, destroying nearly
200 houses and adding new coastline to the island.
Information Contact: Hawaiian Volcano Observatory
(HVO), U.S. Geological Survey, PO Box 51, Hawaii
National Park, HI 96718, USA (URL:
hvo.wr.usgs.gov/; Email: hvo-info@hvomail.wr.usgs.gov).
Tungurahua
Ecuador
1.467°S, 78.442°W: summit elev. 5,023 m
All times are local (= UTC - 5 hours)
The eruption of Tungurahua that began at the end
of December 2003 (BGVN 28:11) continued through
January 2004 (BGVN 29:01). Figure 14 shows an ash
plume emitted on January 2004 in a Moderate
Resolution Imaging Spectroradiometer (MODIS) image.
Figure 14. A NASA MODIS image showing an ash
plume from Tungurahua acquired 14 January 2004. N
is up; the plume's height and length were
undisclosed. Arrow points to Tungurahua and is
along the approximate trend of the densest
portion of the plume. The plume blew NE across
the Andes and remained visible well over the
thickly vegetated lowlands farther E. (Visible
Earth v1 ID 26233.) Courtesy of NASA. Inset map
showing major active Ecuadorian volcanoes courtesy of the USGS.
On 5 February 2004 there was a slight increase in
seismic activity at Tungurahua; steam emissions
rose to low levels, and small lahars traveled
down the volcano's W flank via the Achupashal and
Chontapamba gorges. On 9 February emissions of
steam, gas, and moderate amounts of ash occurred,
deposited to the W in the sectors of Pillate and
San Juan. During mid February, several avalanches
of incandescent volcanic blocks traveled ~1 km
down the volcano's flank. During late February
through mid April 2004, degassing continued at
Tungurahua with occasional explosions of steam,
gas, and ash, producing plumes to ~500 m above the volcano.
On 2, 11, and 15 March lahars traveled through
the Pampas sector. During the night of 28-29
March incandescent material was observed
avalanching on the upper slopes. From 30 March to
3 April, volcanic activity was at relatively low
levels, but emissions of steam and ash occurred,
and incandescence was visible in the crater. On 4
April at 1902 an explosion produced a plume
containing a moderate amount of ash that rose to
800 m above the crater, and on the evenings of 10
and 11 April, incandescence was visible in the crater.
Sulfur-dioxide flux measurements taken on 11
April were the highest measured for several
weeks; 1,600-1,700 metric tons per day. Heavy
rain during the afternoon and night of 13 April
triggered a lahar that cut the La Pampa section of the Banos-Pelileo road.
Volcanic activity at Tungurahua at the end of
April 2004 was at moderate levels. On 21 April, a
column of steam, gas, and ash rose to a height of
~1 km above the volcano and drifted NW. Ash fell
in Bilbao, Cusua, San Juan, Cotalo, Pillate, and
Juive sectors. A plume reached ~0.5 km on 22
April and deposited ash in the towns of Ambato
(to the NW) and Banos (to the N). During the
evening of 24 April, incandescence was visible in
the crater, and incandescent blocks rolled a few
meters down the volcano's NW flank.
Volcano-tectonic earthquakes on 27 and 28 April
preceded a slight increase in the number of
sudden explosions at Tungurahua on 30 April.
According to news reports, ash fell in the towns
of Cotalo, and San Juan (W of the volcano) on 1
and 2 May. The level of seismicity at Tungurahua
decreased on 4 May. On 12 May, an explosion
produced an ash cloud to ~3 km above the volcano
that drifted SW, and on 13 May seismicity
increased moderately, related to the increased
numbers of emissions. Incandescence was visible
at the lava dome during some nights.
From mid May through June, small-to-moderate
emissions of gas, steam, and ash continued at
Tungurahua. The highest rising plume reached ~2.5
km above the volcano on 23 May. On the morning of
19 May a mudflow occurred in the Pampas sector,
but it did not affect the highway. Strombolian
activity was visible in the crater on the evening
of 23 May. During 2-8 June, activity remained
moderate with several weak to moderate
explosions recorded per day. Sporadically
observed gas-and-ash and gas-and-steam plumes
rose up to 1 km above the summit. A strong
explosion on 5 June produced a gas-and-ash plume
that rose 2 km above the summit. All plumes
drifted W. Seismicity remained at moderate
levels. On 3 June, possible lahars were noted on the N and NW flanks.
Several explosions occurred on 10 June, with the
largest rising ~3 km above Tungurahua's summit
and drifting W. A small amount of ash fell in the
Pillate area, and a lahar destroyed a bridge in
the Bibao zone. During mid to late June, there
was a slight increase in volcanic activity at
Tungurahua in comparison to the previous weeks.
There were several emissions of steam, gas, and
moderate amounts of ash, and 5-10 explosions
occurred daily. Seismicity was characterized by long-period earthquakes.
From July through December 2004 the level of
volcanic and seismic activity diminished at
Tungurahua, with sporadic moderate explosions of
ash and gas. The highest rising plume reached
~1.5 km above the volcano. Seismicity was at
relatively low levels. Incandescence in the
crater was observed at night on several
occasions. Some explosions on 20 September
generated plumes with ash, causing ashfall in
Bilbao and Pondoa, and on the evening of 21
September, Strombolian activity was seen, with
volcanic blocks thrown as high as 200 m above the
volcano. On 27 October an explosion produced an
ash column to a height of ~3.5 km above the
volcano. During the evening, ash fell in the
towns of Banos, Runton, and El Salado. Explosions
on 31 October also deposited small amounts of ash
in Bilbao and Motilone, and on 15 November,
incandescence was observed in the crater of the
volcano and explosions generated steam columns
with moderate ash content that rose ~2 km above
the crater and drifted S. During 22-27 December,
activity at Tungurahua consisted of
small-to-moderate explosions, several long-
period earthquakes, and episodes of tremor.
Emissions of steam, gas, and small amounts of ash
rose a maximum of 1.5 km on 22 December.
Increased seismicity and volcanic tremor
registered at Tungurahua during early January
2005. There were eleven signals suggesting
volcanic emissions and one small explosion.
Seismicity then returned to a low level. On 11
January, steam plumes rose ~300 m above the
volcano and extended WNW, and incandescence was
observed emanating from the crater during 12-13
January. On 14 January, a white column of
steam-and-gas was observed that reached a height
of 500 m above the crater and extended to the NW.
A steam- and-gas plume reached a height of
200-300 m above the crater on 16 January, and extended SE.
The Washington Volcanic Ash Advisory Center
(VAAC) reported 18 January that an ash plume
reached ~5.5 km altitude and extended to the E of
Tungurahua's summit for ~15 km. During 19-24
January 2005, there were several emissions from
Tungurahua of steam, gas, and ash. The plumes
that were produced rose to a maximum height of ~1
km above the volcano and drifted in multiple
directions, small amounts of ash falling in the
sectors of Agoyan, San Francisco, Runton, Pondoa,
and Banos. Seismicity was at relatively low
levels. Ash emission from Tungurahua on the
evening of 25 January 2005 deposited a small
amount of ash in the sector of Puela; ash was
deposited on the volcano's N and W flanks on 26
January. The character of the eruption changed on
30 January to low-energy emissions of
predominately steam. This type of activity continued through 31 January.
Volcanic and seismic activity was at low levels
at Tungurahua during the period of February-mid
July 2005. Low- energy plumes were emitted, and
long-period earthquakes were recorded. Ashfall
was reported in towns near the volcano, including
Puela (SW of the volcano), San Juan de Pillate,
Cusuaua, and Quern. On 23 February the daily
sulfur-dioxide flux was 1,200 tons/day. On 27 and
28 February, rains generated lahars in the W zone
of the volcano into the gorges of Cusua and
Bilbao. A moderate explosion occurred 18 April at
2057 that sent incandescent volcanic blocks
rolling down the volcano's flanks. Ash fell S of
the city of Ambato. On 20 and 21 April rain
generated lahars that traveled down the volcano's
W flank near the settlement of Bilbao (8 km W).
An emission on 19 May around 1200 produced an
ash-and- steam plume to ~500 m altitude that
drifted N. On 7 June fine ash fell in the Puela
sector, ~8 km SW of the volcano. On 24 June a
narrow plume was identified in multispectal
satellite imagery about an hour after an ash
eruption was observed by the Instituto Geofisica.
The ash plume was at an altitude of ~5.5 km and
extended 35-45 km W from the summit. On 4 July
2005, low-energy plumes were emitted that rose to
a maximum of ~5.8 km altitude.
Table 4 gives examples of some seismic statistics
for several months during the reporting period
from the Instituto Geofisico-Escuela Politecnica Nacional (IG).
Table 4. Summary of available seismicity (number
of events) at Tungurahua during January
2004-March 2005 as published in IG monthly
reports of March 2004, October 2004, and April
2005. Courtesy of the Instituto Geofisico-Escuela Politecnica Nacional (IG).
Month/Year Long-period
Volcano-tectonic Emission Explosions Hybrid
Jan
2004 365 6 217 28 0
Feb
2004 255 8 147 16 0
Mar
2004 123 7 123 2 0
Aug
2004 620 5 142 22 0
Sep
2004 674 9 119 43 0
Oct
2004 390 14 168 53 0
Jan
2005 138 8 92 6 0
Feb
2005 113 20 29 0 0
Mar
2005 54 20 1 0 0
Background. Tungurahua, a steep-sided,
andesitic-dacitic stratovolcano that towers more
than 3 km above its northern base, is one of
Ecuador's most active volcanoes. Three major
volcanic edifices have been sequentially
constructed since the mid-Pleistocene over a
basement of metamorphic rocks. Tungurahua II was
built within the past 14,000 years following the
collapse of the initial edifice. Tungurahua II
itself collapsed about 3000 years ago and
produced a large debris-avalanche deposit and a
horseshoe-shaped caldera open to the west, inside
which the modern glacier-capped stratovolcano
(Tungurahua III) was constructed. Historical
eruptions have all originated from the summit
crater. They have been accompanied by strong
explosions and sometimes by pyroclastic flows and
lava flows that reached populated areas at the
volcano's base. Prior to a long-term eruption
beginning in 1995 that caused the temporary
evacuation of the city of Banos at the foot of
the volcano, the last major eruption had occurred
from 1916 to 1918, although minor activity continued until 1925.
Information Contacts: Geophysical Institute (IG),
Escuela Politecnica Nacional, Apartado
17-01-2759, Quito, Ecuador (URL:
www.igepn.edu.ec/); Washington Volcanic
Ash Advisory Center (VAAC), Satellite Analysis
Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science
Center Room 401, 5200 Auth Rd., Camp Springs, MD
20746 USA (URL: www.ssd.noaa.gov/);
Jacques Descloitres, MODIS Rapid Response Team,
NASA/GSFC, 8800 Greenbelt Road, Greenbelt, MD
20771, USA (URL:
earthobservatory.nasa.gov/Natur...ards/;
rapidfire.sci.gsfc.nasa.gov/).
McDonald Islands
Southern Indian Ocean
53.03°S, 72.60°E; summit elev. 230 m
The following report comes from Matt Patrick of
the HIGP Thermal Alerts Team. Two night-time
ASTER images (Band 10, 8.3 microns, at 90 m pixel
size) of McDonald Island show activity centered
on the NW shore of the island. The December 2002
image was examined some months ago, but it was
not determined whether the long-wave infrared
(IR) anomaly was genuine, since it was relatively
low intensity and there was no anomaly in the
shortwave IR. The most recent ASTER image (12
July 2005) shows a somewhat larger long-wave IR
anomaly, but more importantly, there are five
pixels in the shortwave IR (Band 9, 2.4 microns;
not shown) which are saturated, indicating this
is a significantly hot target. Based upon
McDonald's typical activity, the anomaly probably
reflects low-level effusive activity.
The first and only MODVOLC alert pixel showed up
in November 2004 (BGVN 29:12). These ASTER images
show that recent activity is centered around the
NW flank of the island, very close to shore.
Comparing the July 2005 image with the December
2002 image, there might be an indication of the
shoreline growing westward, but it is hard to
tell for sure with this resolution (90 meters).
The location of this activity is generally
consistent with recent BGVN reports: in 1999
steaming was observed on the N-NE part of the
island (BGVN 24:01), and a recent Landsat ETM
image indicated that island construction over the
last two decades has expanded the northern
portion of the volcano (BGVN 26:02 and 27:12).
Andrew Tupper noted that he found the hot spot
identification plausible. The question of edifice
collapse and possible tsunami generation
associated with McDonald Islands has recently
been a subject of interest but little technical
information is available on topics such as
edifice morphology and slope stability.
Background. Historical eruptions have greatly
modified the morphology of the McDonald Islands,
located on the Kerguelen Plateau about 75 km west
of Heard Island. The largest island, McDonald, is
composed of a layered phonolitic tuff plateau cut
by phonolitic dikes and lava domes. A possible
nearby active submarine center was inferred from
phonolitic pumice that washed up on Heard Island
in 1992. Volcanic plumes were observed in
December 1996 and January 1997 from McDonald
Island. During March of 1997 the crew of a vessel
that sailed near the island noted vigorous
steaming from a vent at the northern side of the
island along with possible pyroclastic deposits
and lava flows. A satellite image taken in
November 2001 showed the island to have more than
doubled in area since previous reported
observations in November 2000. The high point of
the island group had shifted to the northern end
of McDonald Island, which had merged with Flat Island.
Information Contacts: Matt Patrick, HIGP Thermal
Alerts Team, Hawai'i Institute of Geophysics and
Planetology (HIGP) / School of Ocean and Earth
Science and Technology (SOEST), University of
Hawai'i, 2525 Correa Road, Honolulu, HI 96822,
USA (hotspot.higp.hawaii.edu/, Email:
patrick@higp.hawaii.edu); Andrew Tupper, Darwin
Volcanic Ash Advisory Centre (VAAC), Commonwealth
Bureau of Meteorology, Northern Territory
Regional Office, PO Box 40050, Casuarina, NT
0811, Australia (URL:
www.bom.gov.au/info/vaac/; Email: darwin.vaac@bom.gov.au).
__________________________________________________________
Global Volcanism Program, NHB E-421 Tel: (202) 633-1800
Smithsonian Institution Fax: (202) 357-2476
Washington, DC 20560-0119 Email: gvp@si.edu
Internet: www.volcano.si.edu/
