World's most dangerous volcanoes can erupt much more quickly than believed

Washington, October 8 (ANI): A new study has revealed that some of the world's most dangerous volcanoes can erupt much more quickly than scientists had suspected.

According to a report in National Geographic News, the study took into account the massive 2008 eruption of Chile's Chaiten volcano.

When townspeople at the base of the Chaiten volcano first felt earthquakes on April 30, 2008, they had only 30 hours to get out before the long-dormant volcano began to blow its top.

On May 3, 2008, magma rocketed up through Earth's crust, moving .1 miles (5 kilometers) up to the Chaitin volcano's surface in only about four hours.

An enormous eruption column soared 12 miles (19 kilometers) into the sky.

Thousands of Chaiten villagers had enough time to evacuate. But future victims who live in the shadows of these so-called rhyolitic volcanoes may not be so lucky.

Rhyolitic volcanoes are largely fueled by a silica-based, very flow-resistant magma and they tend to build pressure over time before erupting violently.

Rhyolitic volcanoes erupt so infrequently that scientists hadn't had a chance to observe one until Chaiten.

The eruptions may go 10,000 years between episodes.

"The largest eruptions on the planet have been rhyolitic," said study co-author Jonathan Castro of the Institut des Sciences de la Terre in Orleans, France. "So, you might have fewer of these volcanoes, but they pack a way bigger punch," he added.

Castro and colleagues studied crystalline evidence of Chaiten's pre-eruption magma temperature, pressure, and water content to discover how the volcano had erupted so quickly.

Deep inside a rhyolitic volcano, the mostly silica-based magma is thinned by water and other fluids.

Pressure from above keeps the water in place.

But as the magma rises toward the surface, the pressure eases until nearly all the water is removed-making the material one of the most viscous liquids known in nature.

Meanwhile, the extracted water forms a layer of bubbles, increasing pressure on the surrounding sticky magma. Eventually, that built-up pressure breaks to the surface in an explosive eruption.

Ongoing eruptions are continuing to rebuild Chaiten's dome.

"Fine ash and larger blocks, up to the size of a house, come rumbling out," said study co-author Donald Dingwell, of the University of Munich in Germany.

"They can go straight up or tumble down the side of the mountain. Those pyroclastic flows are very hot and very fast. They can asphyxiate you, burn you, bury you alive, or crush you under debris," he added. (ANI)