University Park PA (SPX) Jan 26, 2009
When volcanoes erupt, pinpointing the regions at high risk for lethal hazards and deciding whether or not to evacuate a resistant population comprise the most difficult problems faced by hazards managers. Now a team of volcanologists has a program that maps potential problem areas quickly, taking much of the guesswork out of decision making and evacuations.
"We wanted to be able to predict the areas affected by pyroclastic flows from volcanoes," said Christina Widiwijayanti, post-doctoral fellow in geosciences. "Pyroclastic flows and surges are the phenomena that kill most people when volcanoes erupt."

A pyroclastic flow consists of hot rocks, ash and superheated gases that rapidly flow down from the area of dome collapse on a volcano. Pyroclastic surges are similar, but less dense. They are a kind of hot ash hurricane that can escape the confines of river valleys. Both types of currents are dangerous and frequently lethal.

"In many volcanic crises, a hazard map for pyroclastic flows and surges is sorely needed, but limited time, exposures or safety aspects may preclude fieldwork, and insufficient computational time or baseline data may be available for adequately reliable dynamic simulations of future pyroclastic flow or surge events," the researchers note in a paper published in the Bulletin of Volcanology, Online First.

The researchers, working with Steve P. Schilling, U.S. Geological Survey Cascades Volcano Observatory, looked at an existing procedure created by Schilling called LAHARZ, a geographical information system (GIS) method intended to map hazard zones for volcano-induced mudflows.

"The approach worked for water-saturated mud flows, we thought maybe it would work for hot pyroclastic flows," said Barry Voight, professor emeritus of geosciences. "So we looked at the eruption data and developed some new ways of forecasting areas of impact, particularly for the ash hurricanes."

The researchers used data from eruptions of a variety of volcanoes including the Soufriere Hills Volcano, Montserrat; Mount Merapi, Indonesia; Mount Unzen, Japan, and Colima, Mexico to develop a predictive equation for mapping the hazard. The equation considered the cross sectional area of the flows, the area covered and the amount of material in the flow, and is embedded in the GIS.

"What we are doing is looking at the volcano to see, for each valley system, how far the hot flows of rock and ash can come," said Dannie Hidayat, post doctoral fellow in geosciences. "We can outline the area of potential surge damage and this can be used by decision makers on whether to evacuate or to put people on high alert to evacuate."

Widiwijayanti and Hidayat have personal interests in volcanoes having grown up in Indonesia in close proximity to dangerous erupting volcanoes. Indonesia has 129 active volcanoes. The slopes of Mount Merapi are the home of a quarter million people and Widiwijayanti's family home is within reach of Merapi ash falls.

"Using this program, we can produce maps long before the eruption takes place and they can be kept on the shelf for immediate use, or we can produce maps as needed as soon as there is an indication of impending pyroclastic explosions," said Widiwijayanti.

The program creates maps that outline where the rock and ash will flow for different prospective volumes of material expelled. The volumes are color coded. Also included are mapped lines that indicate the extent of the hot ashy surge for both high and low volumes.

Currently, the program will map hazard zones for pyroclastic flows that go outward and down from the volcano's dome, but the researchers believe that it could also be applied to those pyroclastic eruptions that are column explosions, throwing up mixtures of rock, ash and gas into the air before they come down and form hot radial currents.

"The topology data is available online at good resolution for worldwide sites, so anyone who has GIS can run the simulation," said Widiwijayanti.

This method has already been used twice in eruption crises: once at Merapi in 2006 and in Montserrat in 2006-2009 to quickly and effectively create pyroclastic flow maps.

"I expect this method to make a difference in volcano hazards mitigation," said Voight.

"These maps can be created quickly, in a few days and e-mailed anywhere in the world. We do not need anyone on the ground to study the situation nor do we need a physics-based model to obtain robust curves. This approach saves time and saving time can save lives. We can now avoid being 'too little and too late' in our mitigation response."

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For the first time, scientists have been able to “see” and trace lightning inside a plume of ash spewing from an actively erupting volcano.

When Alaska's Mount Redoubt volcano began rumbling back to life in January, a team of researchers scrambled to set up a system called a Lightning Mapping Array that would be able to peer through the dust and gas of any eruption that occurred to the lightning storm happening within. Lightning is known to flash in the tumultuous clouds belched out during volcanic eruptions.

The lightning produced when Redoubt finally erupted on March 22 was "prolific," said physicist Paul Krehbiel of New Mexico Tech. Check out the image.


"The lightning activity was as strong or stronger than we have seen in large Midwestern thunderstorms," Krehbiel said. "The radio frequency noise was so strong and continuous that people living in the area would not have been able to watch broadcast VHF television stations."

Lightning mapping arrays are increasingly being used by meteorologists to issue weather warnings, but have only been deployed at volcanoes twice before.

Thousands of individual segments of a single lightning stroke can be mapped with these arrays, and later analyzed to reveal how lightning initiates and spreads through a thunderstorm, or in a volcanic plume.

After setting up the arrays, researchers waited nearly two months for Redoubt's first eruption, but the wait was worth it.

"For the first time, we had the Lightning Mapping Array on site before the initial eruption," said scientist Sonja Behnke of New Mexico Tech.

The eruptions that continued to occur on March 22 and 23 provided plenty of data, and the arrays returned dramatic information about the electricity created within volcanic plumes, and the resulting lightning. As of today, Redoubt has erupted several times since its initial eruption on March 22.

"The data will allow us to better understand the electrical charge structure inside a volcanic plume," said scientist Ron Thomas of New Mexico Tech. "That should help us learn how the plume is becoming electrified, and how it evolves over time."

A recent study in the journal Nature found that volcanic plumes spin like tornadic thunderstorms, a finding which helps to explain the lightning storms, as well as the waterspouts and dust devils produced by some volcanic plumes.

The New Mexico Tech researchers plan to compare the Redoubt data with observations taken from Chaiten Volcano in Chile last year. The project was funded by the National Science Foundation.

Redoubt hasn't finished making noise yet; after quieting down for a few days, Redoubt exploded again, with the last major eruption occurring on March 28. Scientists at the Alaska Volcano Observatory expect the eruptions will continue periodically for weeks to months.

www.livescience.com

Columbus OH (SPX) Oct 27, 2009
Researchers here have discovered the pivotal role that volcanoes played in a deadly ice age 450 million years ago. Perhaps ironically, these volcanoes first caused global warming - by releasing massive amounts of carbon dioxide into the atmosphere. When they stopped erupting, Earth's climate was thrown off balance, and the ice age began.
The discovery underscores the importance of carbon in Earth's climate today, said Matthew Saltzman, associate professor of earth sciences at Ohio State University.

The results will appear in the journal Geology, in a paper now available online.

Previously, Saltzman and his team linked this same ice age to the rise of the Appalachian Mountains. As the exposed rock weathered, chemical reactions pulled carbon from Earth's atmosphere, causing a global cooling which ultimately killed two-thirds of all species on the planet.

Now the researchers have discovered the other half of the story: giant volcanoes that formed during the closing of the proto-Atlantic Ocean - known as the Iapetus Ocean - set the stage for the rise of the Appalachians and the ice age that followed.

"Our model shows that these Atlantic volcanoes were spewing carbon into the atmosphere at the same time the Appalachians were removing it," Saltzman explained. "For nearly 10 million years, the climate was at a stalemate. Then the eruptions abruptly stopped, and atmospheric carbon levels fell well below what they were in the time before volcanism. That kicked off the ice age," he said.

This is the first evidence that a decrease in carbon from volcanic degassing - combined with continued weathering of the Appalachians - caused the long-enigmatic glaciation and extinction in the Ordovician period.

Here is the picture the researchers have assembled: 460 million years ago, during the Ordovician, volcanoes along the margin of what is now the Atlantic Ocean spewed massive amounts carbon dioxide into the atmosphere, turning the world into a hothouse. Lava from those volcanoes eventually collided with North America to form the Appalachian Mountains.

Acid rain - rich in carbon dioxide - pelted the newly exposed Appalachian rock and wore it away. Chemical reactions trapped the carbon in the resulting sediment, which formed reefs in the vast seas that covered North America.

For about 10 million years, the volcanoes continued to add carbon to the atmosphere as the Appalachians removed it, so the hothouse conditions remained stable. Life flourished in the warm oceans, including abundant species of trilobites and brachiopods.

Then, 450 million years ago, the eruptions stopped. But the Appalachians continued weathering, and atmospheric carbon levels plummeted. The Earth swung from a hothouse to an icehouse.

By 445 million years ago, glaciers had covered the south pole on top of the supercontinent of Gondwana (which would eventually break apart to form the continents of the southern hemisphere). Two-thirds of all species had perished.

When they started this research, Saltzman and his team knew that Earth's climate must have changed drastically at the end of the Ordovician. But they didn't know for certain that volcanoes were the driving force, explained Seth Young, who did this research for his doctoral degree at Ohio State. He is now a postdoctoral researcher at Indiana University.

"This was not necessarily what we expected when we started investigating, but as we combined our data sources, the story began to fall into place," Young said.

Using a computer model, they drew together measurements of isotopes of chemical elements - including strontium from rocks in Nevada and neodymium from rocks in Virginia and Pennsylvania - with measurements of volcanic ash beds in the same locations. Then they factored in temperature models developed by other researchers.

The ash deposits demonstrated when the volcanoes stopped erupting; the strontium levels indicated that large amounts of volcanic rock were being eroded and the sediment was flooding Earth's oceans during this time; and the neodymium levels pinpointed the Appalachians as the source of the sediment.

The new findings mesh well with what scientists know about these ancient proto-Atlantic volcanoes, which are thought to have produced the largest eruptions in Earth's history. They issued enough lava to form the Appalachians, enough ash to cover the far ends of the earth, and enough carbon to heat the globe. Atmospheric carbon levels grew 20 times higher than they are today.

This study shows that when those volcanoes stopped erupting, carbon levels dropped, and the climate swung dramatically back to cold. The timing coincides with today's best estimates of temperature fluctuations in the Ordovician.

"The ash beds start building up at the same time the Appalachian weathering begins, but then the record of volcanism ends, and the temperature drops," Saltzman said. "Knowing these details can help us understand how carbon in the atmosphere is changing Earth's climate today."

Next, the researchers will examine the role of the ancient volcanic ash more closely. While the ash was in the atmosphere - before it settled around the globe - it might have blotted out the sun, and cooled the earth somewhat. Saltzman and his team want to make some estimate of this short-term cooling effect to refine their computer model.

Meanwhile, Young is just starting to re-analyze the same rock samples, this time looking for a different isotope - sulfur. This, he hopes, will offer clues to how much oxygen was in the oceans, and how that oxygen may have affected life in the Ordovician.


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