World's Largest Calderas

The Biggest of the "supervolcanoes"

Caldera name: La Pacana Country:Chile Location:23.10 S
Size (km): 67.25 W 60 x 35 Most recent eruption:Pliocene


Caldera name:Pastos Country:Grandes Bolivia Location:21.45 S
Size (km):67.51 W 50 x 40 Most recent eruption:8.3 Ma


Caldera name:Kari Kari Country:Bolivia Location:19.43 S
Size(km):65.38 W 30 Most recent eruption:Unknown


Caldera name:Cerro Galan Country:Argentina Location: 25.57 S
Size (km):65.57 W 32 Most recent eruption:2.5 Ma


Awasa Ethiopia 7.18 N 38.48 E 40 x 30 Unknown

Toba Indonesia 2.60 N 98.80 E 100 x 35 74 ka

Tondano Indonesia 1.25 N 124.85 E 30 x 20 Quaternary


Maroa/
Whakamaru NewZealand 38.55 S 176.05 E 40 x 30 500 ka

Taupo New Zealand 38.78 S 176.12 E 35 1,800 yr

Yellowstone1 USA-WY 44.58 N 110.53 W 85 x 45 630 ka

La Garita USA-CO 37.85 N 106.93 W 75 x 35 27.8 Ma

Emory USA-NM 32.8 N 107.7 W 55 x 25 33 Ma

Bursum USA-NM 33.3 N 108.5 W 40 x 30 28-29 Ma

Longridge
(McDermitt)1 USA-OR 42.0 N 117.7 W 33 ~16 Ma

Socorro USA-NM 33.96 N 107.10 W 35 x 25 33 Ma

Timber
Mountain USA-NV 37 N 116.5 W 30 x 25 11.6 Ma

Chinati
Mountains USA-TX 29.9 N 104.5 W 30 x 20 32-33 Ma

Long Valley USA-CA 37.70 N 118.87 W 32 x 17 50 ka

greater Maly
Semiachik/Pirog2 Russia 54.11 N 159.65 E 50 ~50 ka

greater Bolshoi
Semiachik2 Russia 54.5 N 160.00 E 48 x 40 ~50 ka

greater
Ichinsky2 Russia 55.7 N 157.75 E 44 x 40 ~50 ka

greater
Pauzhetka2 Russia 51 N 157 E ~40 300 ka

greater
Ksudach2 Russia 51.8 N 157.54 E ~35 ~50 ka



* Ma is million years ago, ka is thousand years ago, Pliocene is 5.3-1.8 Ma, Quaternary is 1.8-0 Ma.
1Yellowstone and Longridge are the ends of a chain of several large calderas extending beneath the Snake River Plain, each comparable in size.
2The Russian calderas are informally named here for the smaller modern calderas and active volcanoes that lie within them.

Source: Cambridge Volcanology Group caldera database


geology.about.com/library/b...lderas.htm

Ancient "Supervolcano" Rocked Washington State
Richard A. Lovett
for National Geographic News

February 6, 2007
An ancient "supervolcano" in what is now Washington State spewed steam and billowed ash in amounts that dwarf the eruption of Mount St. Helens in 1980, new research shows.

The blow-up occurred in two major bursts about 3.7 million years ago in the northern Cascade Range, creating flows of searing-hot gas and belching out some 33 cubic miles (137 cubic kilometers) of ash.

It wasn't the first eruption to occur there, said David Tucker, a research associate at Western Washington University. And it wasn't the last either.

The newly discovered mega-eruption brings to six the tally of ancient volcanoes known to have blown in the Cascades, Tucker said.

"We know there were at least some small volcanoes [at the site]," he said.

"We don't know what kind, because they were obliterated. Now they exist merely as little bits of rock."

The blasts, he added, would have killed all life for several miles around and dumped ash over a vast area downwind.

"These are big eruptions—on the small end of what have been called supervolcanoes," Tucker said.

"If something went off like that today, a long way into British Columbia would be severely impacted." (See Washington State map.)

If it happened in the southern end of the Cascades in Oregon, "thick ash would probably fall in the Midwest [U.S.]."

Tucker's research appears in the March/April issue of the Geological Society of America Bulletin.

At Least Six Giant Eruptions

The first of the two eruptions that rocked the northern Cascades formed a giant crack, Tucker said.

When the crack widened, the ground on one side dropped like a trap door swinging down. The section of earth fell more than 3,000 feet (1,000 meters).

Vast quantities of ash then filled the hole, and rivers of ash and superheated air rushed away with enough momentum to flow over surrounding mountains, incinerating everything in their paths.

(See an interactive feature on how volcanoes work.)

The second eruption occurred about a hundred thousand years later, when the upper end of the trap door dropped, forming a roughly rectangular crater measuring 5 miles by 2.5 miles (8 kilometers by 4 kilometers).

The best known ancient eruption to have occurred in the Cascades is the one that produced Oregon's Crater Lake, only 7,700 years ago. (Download a wallpaper photo of Crater Lake.)

"I suspect there are a number of others," Tucker said. "Part of my research in the future will focus on finding more."

He compared the Cascades supervolcano event to the eruption of the Indonesian island of Krakatau (or Krakatoa), which exploded in 1883, killing 36,000 people.

"Actually, Krakatoa was small compared to [the ancient Cascades eruption]."

Krakatau ejected approximately 10 cubic miles (25 cubic kilometers) of rock and ash when it blew its top.

The two eruptions described by Tucker involved a total of about 30 cubic miles (130 cubic kilometers) of magma "in a period of probably a day or two [each]," Tucker said.

Since then the site has been quiet, as volcanic activity has shifted 15 miles (25 kilometers) southwest, to the present location of 10,778-foot (3,285-meter) Mount Baker, near the city of Bellingham.

No one knows if Mount Baker, or another peak in the Cascades, might someday produce a similar mammoth eruption, Tucker said.




news.nationalgeographic.com/news....html

Geologists Reveal Secrets Behind Supervolcano Eruption

Newswise — Researchers at Rensselaer Polytechnic Institute have discovered what likely triggered the eruption of a “supervolcano” that coated much of the western half of the United States with ash fallout 760,000 years ago.

Using a new technique developed at Rensselaer, the team determined that there was a massive injection of hot magma underneath the surface of what is now the Long Valley Caldera in California some time within 100 years of the gigantic volcano’s eruption. The findings suggest that this introduction of hot melt led to the immense eruption that formed one of the world’s largest volcanic craters or calderas.

The research, which is featured in the March 2007 edition of the journal Geology, sheds light on what causes these large-scale, explosive eruptions, and it could help geologists develop methods to predict such eruptions in the future, according to David Wark, research professor of earth and environmental sciences at Rensselaer and lead author of the paper.

The 20-mile-long Long Valley Caldera was created when the supervolcano erupted. The geologists focused their efforts on Bishop Tuff, an expanse of rock that was built up as the hot ash cooled following the eruption. The researchers studied the distribution of titanium in quartz crystals in samples taken from Bishop Tuff.

A team from Rensselaer previously discovered that trace levels of titanium can be analyzed to determine the temperature at which the quartz crystallized. By monitoring titanium, Wark and his colleagues confirmed that the outer rims of the quartz had formed at a much hotter temperature than the crystal interiors. The researchers concluded that after the interiors of the quartz crystals had grown, the magma system was “recharged” with an injection of fresh, hot melt. This caused the quartz to partly dissolve, before starting to crystallize again at a much higher temperature.

Analyses of titanium also revealed that the high-temperature rim-growth must have taken place within only 100 years of the massive volcano’s eruption. This suggests that the magma recharge so affected the physical properties of the magma chamber that it caused the supervolcano to erupt and blanket thousands of square miles with searing ash.

“The Long Valley Caldera has been widely studied, but by utilizing titanium in quartz crystals as a geothermometer we were able to provide new insight into the reasons for its last huge eruption,” Wark said. “This research will help geologists understand how supervolcanoes work and what may cause them to erupt, and this in turn may someday help predict future eruptions.”

The research was funded through a grant from the National Science Foundation.

Wark was assisted in his research by Wes Hildreth of the U.S. Geological Survey; Frank Spear, Rensselaer professor of earth and environmental sciences and department chair; Bruce Watson, Institute Professor at Rensselaer, and Daniele Cherniak, research associate professor of earth and environmental sciences at Rensselaer.

About Rensselaer
Rensselaer Polytechnic Institute, founded in 1824, is the nation’s oldest technological university. The university offers bachelor’s, master’s, and doctoral degrees in engineering, the sciences, information technology, architecture, management, and the humanities and social sciences. Institute programs serve undergraduates, graduate students, and working professionals around the world. Rensselaer faculty are known for pre-eminence in research conducted in a wide range of fields, with particular emphasis in biotechnology, nanotechnology, information technology, and the media arts and technology. The Institute is well known for its success in the transfer of technology from the laboratory to the marketplace so that new discoveries and inventions benefit human life, protect the environment, and strengthen economic development.


www.newswise.com/articles/view/527849/

Crater of Ancient Supervolcano Discovered at Kamchatka
Eruption of such a volcano could be ten thousand times more powerful than that of an ordinary one

VLADIVOSTOK, April 2, vladivostoktimes.com Scientists have discovered caldera of an ancient supervolcano at Kamchatka, RIA Novosti reports.

"The eruption of the Kamchatka supervolcano took place more than about a million and a half years ago," Vladimir LEONOV, the Scientific Secretary of the Institute of Volcanology and Seismology of the Far Eastern Branch of the Russian Academy of Sciences, said to RIA PrimaMedia.

Now the volcano has "cooled off," so some specialists say it would be incorrect to speak of any possibility of new eruptions.

The report on the first study of the newly-found giant caldera was presented at the scientific conference dated to Volcanologist's Day, March 30, held in Petropavlovsk-Kamchatskiy.

According to Mr. LEONOV, people have known no such geological formations at Kamchatka up till now. The discovered caldera is a giant oval 35 kilometres long. The caldera is stretched between the head of the Paratunka River and Banniye hot springs. Scientists suppose that these particular springs might be heated by the warmth of the ancient super-volcano.

Supervolcanoes' calderas have kindled scientists' interest all over the world recently. The most well-known one is the Yellowstone Caldera measuring about 55 by 72 kilometres.

"Judging by geological data, the eruptions of the super-volcano happened there with an interval of around 640 thousand years. About 640 thousand years have passed since the time of the last eruption, and if no changes have occurred in the mechanism of the super-volcano, we can expect a new powerful eruption," a representative of the Institute said.

Supervolcanoes are giant cavities beneath the earth's surface that are continuously filled with magma that arrives from the bosom of the earth. The pressure formed there can induce eruption ten thousand times more powerful than any known volcanic eruptions. On the surface, supervolcanoes are recognized by calderas - giant craters that form when magma chambers sink.

The last supervolcano eruption occurred 74 thousand years ago in the region where Sumatra is located today. Then the average temperature in the Northern Hemisphere fell 21 degrees Centigrade. Some researchers also speculate that most living things perished then, brushing the evolution 2 million years back.


vladivostoktimes.ru/show.php

Researchers uncover 'stirring' secrets of deadly supervolcanoes
Researchers from The University of British Columbia and McGill University have simulated in the lab the process that can turn ordinary volcanic eruptions into so-called “supervolcanoes.”


The study was conducted by Ben Kennedy and Mark Jellinek of UBC’s Dept. of Earth and Ocean Sciences, and John Stix of McGill’s Dept. of Earth and Planetary Sciences. Their results are published this week in the journal Nature Geoscience.

Supervolcanoes are orders of magnitude greater than any volcanic eruption in historic times. They are capable of causing long-lasting change to weather, threatening the extinction of species, and covering huge areas with lava and ash.

Using volcanic models made of Plexiglas filled with corn syrup, the researchers simulated how magma in a volcano’s magma chamber might behave if the roof of the chamber caved in during an eruption.

“The magma was being stirred by the roof falling into the magma chamber,” says Stix. “This causes lots of complicated flow effects that are unique to a supervolcano eruption.”

“There is currently no way to predict a supervolcano eruption,” says Kennedy, a post-doctoral fellow at UBC and lead author on the paper. “But this new information explains for the first time what happens inside a magma chamber as the roof caves in, and provides insights that could be useful when making hazard maps of such an eruption.”

The eruption of Mount Tambora in Indonesia in 1815 – the only known supervolcano eruption in modern history – was 10 times more powerful than Krakatoa and more than 100 times more powerful than Vesuvius or Mount St. Helens. It caused more than 100,000 deaths in Indonesia alone, and blew a column of ash about 70 kilometres into the atmosphere. The resulting disruptions of the planet’s climate led 1816 to be christened “the year without summer.”

“And this was a small supervolcano,” says Stix. “A really big one could create the equivalent of a global nuclear winter. There would be devastation for many hundreds of kilometres near the eruption and there would be would be global crop failures because of the ash falling from the sky, and even more important, because of the rapid cooling of the climate.”

There are potential supervolcano sites all over the world, most famously under Yellowstone National Park in Wyoming, the setting of the 2005 BBC/ Discovery Channel docudrama Supervolcano, which imagined an almost-total collapse of the world economy following an eruption.

Source: University of British Columbia



www.physorg.com/news131289102.html

Supervolcano may be brewing beneath Mount St Helens

From New Scientist:

IS A supervolcano brewing beneath Mount St Helens? Peering under the volcano has revealed what may be an extraordinarily large zone of semi-molten rock, which would be capable of feeding a giant eruption.

Magma can be detected with a technique called magnetotellurics, which builds up a picture of what lies underground by measuring fluctuations in electric and magnetic fields at the surface. The fields fluctuate in response to electric currents travelling below the surface, induced by lightning storms and other phenomena. The currents are stronger when magma is present, since it is a better conductor than solid rock.

Graham Hill of GNS Science, an earth and nuclear science institute in Wellington, New Zealand, led a team that set up magnetotelluric sensors around Mount St Helens in Washington state, which erupted with force in 1980. The measurements revealed a column of conductive material that extends downward from the volcano. About 15 kilometres below the surface, the relatively narrow column appears to connect to a much bigger zone of conductive material.

This larger zone was first identified in the 1980s by another magnetotelluric survey, and was found to extend all the way to beneath Mount Rainier 70 kilometres to the north-east, and Mount Adams 50 kilometres to the east. It was thought to be a zone of wet sediment, water being a good electrical conductor.

However, since the new measurements show an apparent conduit connecting this conductive zone to Mount St Helens - which was undergoing a minor eruption of semi-molten material at the time the measurements were made - Hill and his colleagues now think the conductive material is more likely to be a semi-molten mixture. Its conductivity is not high enough for it to be pure magma, Hill says, so it is more likely to be a mixture of solid and molten rock.

Gary Egbert of Oregon State University in Corvallis, who is a magnetotellurics specialist but not a member of Hill's team, is cautious about the idea of a nascent supervolcano where Mount St Helens sits. "It seems likely that there's some partial melt down there," given that it is a volcanic area, he says. "But part of the conductivity is probably just water."

If the structure beneath the three volcanoes is indeed a vast bubble of partially molten rock, it would be comparable in size to the biggest magma chambers ever discovered, such as the one below Yellowstone National Park.

Every few hundred thousand years, such chambers can erupt as so-called supervolcanoes - the Yellowstone one did so about 640,000 years ago. These enormous eruptions can spew enough sunlight-blocking ash into the atmosphere to cool the climate by several degrees Celsius.

Could Mount St Helens erupt like this? "A really big, big eruption is possible if it is one of those big systems like Yellowstone," Hill says. "I don't think it will be tomorrow, but I couldn't try to predict when it would happen."

Further measurements probing the structure of the crust beneath the other volcanoes in the area could help determine if the zone connects to them all, Hill says. He presented his team's results on 27 May at the Joint Assembly geophysics meeting in Toronto, Canada.



www.newscientist.com/article...ens.html

'Rosetta Stone' of supervolcanoes discovered in Italian Alps
September 21st, 2009

Scientists have found the "Rosetta Stone" of supervolcanoes, those giant pockmarks in the Earth's surface produced by rare and massive explosive eruptions that rank among nature's most violent events. The eruptions produce devastation on a regional scale -- and possibly trigger climatic and environmental effects at a global scale.

A fossil supervolcano has been discovered in the Italian Alps' Sesia Valley by a team led by James E. Quick, a geology professor at Southern Methodist University. The discovery will advance scientific understanding of active supervolcanoes, like Yellowstone, which is the second-largest supervolcano in the world and which last erupted 630,000 years ago.

A rare uplift of the Earth's crust in the Sesia Valley reveals for the first time the actual "plumbing" of a supervolcano from the surface to the source of the magma deep within the Earth, according to a new research article reporting the discovery. The uplift reveals to an unprecedented depth of 25 kilometers the tracks and trails of the magma as it moved through the Earth's crust.

Supervolcanoes, historically called calderas, are enormous craters tens of kilometers in diameter. Their eruptions are sparked by the explosive release of gas from molten rock or "magma" as it pushes its way to the Earth's surface.

Calderas erupt hundreds to thousands of cubic kilometers of volcanic ash. Explosive events occur every few hundred thousand years. Supervolcanoes have spread lava and ash vast distances and scientists believe they may have set off catastrophic global cooling events at different periods in the Earth's past.

Sesia Valley's caldera erupted during the "Permian" geologic time period, say the discovery scientists. It is more than 13 kilometers in diameter.

"What's new is to see the magmatic plumbing system all the way through the Earth's crust," says Quick, who previously served as program coordinator for the Volcano Hazards Program of the U.S. Geological Survey. "Now we want to start to use this discovery. We want to understand the fundamental processes that influence eruptions: Where are magmas stored prior to these giant eruptions? From what depth do the eruptions emanate?"

Sesia Valley's unprecedented exposure of magmatic plumbing provides a model for interpreting geophysical profiles and magmatic processes beneath active calderas. The exposure also serves as direct confirmation of the cause-and-effect link between molten rock moving through the Earth's crust and explosive volcanism.

"It might lead to a better interpretation of monitoring data and improved prediction of eruptions," says Quick, lead author of the research article reporting the discovery, "Magmatic plumbing of a large Permian caldera exposed to a depth of 25 km.," in Geology.

Calderas, which typically exhibit high levels of seismic and hydrothermal activity, often swell, suggesting movement of fluids beneath the surface.

"We want to better understand the tell-tale signs that a caldera is advancing to eruption so that we can improve warnings and avoid false alerts," Quick says.

To date, scientists have been able to study exposed caldera "plumbing" from the surface of the Earth to a depth of only 5 kilometers. Because of that, scientific understanding has been limited to geophysical data and analysis of erupted volcanic rocks. Quick likens the relevance of Sesia Valley to seeing bones and muscle inside the human body for the first time after previously envisioning human anatomy on the basis of a sonogram only.

"We think of the Sesia Valley find as the 'Rosetta Stone' for supervolcanoes because the depth to which rocks are exposed will help us to link the geologic and geophysical data," Quick says. "This is a very rare spot. The base of the Earth's crust is turned up on edge. It was created when Africa and Europe began colliding about 30 million years ago and the crust of Italy was turned on end."

Bristish researchers introduced the term "supervolcano" in the last 10 years. Scientists have documented fewer than two dozen caldera eruptions in the last 1 million years.

Besides Yellowstone, other monumental explosions have included Lake Toba on Indonesia's Sumatra island 74,000 years ago, which is believed to be the largest volcanic eruption on Earth in the past 25 million years.

Described as a massive climate-changing event, the Lake Toba eruption is thought to have killed an estimated 60% of humans alive at the time.

Another caldera, and one that remains active, Long Valley in California erupted about 760,000 years ago and spread volcanic ash for 600 cubic kilometers. The ash blanketed the southwestern United States, extending from California to as far west as Nebraska.

"There will be another supervolcano explosion," Quick says. "We don't know where. Sesia Valley could help us to predict the next event."

Source: Southern Methodist University (news : web)



www.physorg.com/news172766088.html