Chilean eruption highlights risk from 'rhyolitic' volcanoes

Oct 07, 2009
A cow is covered with ash of the Chilean Chaiten volcano near the border town of Los Cipreses, in the Argentine Patagonia, seen here in 2008. Magma from a Chilean volcano shot through Earth's crust at around a metre (3.25 feet) per second, a speed highlighting the perils from so-called rhyolitic volcanoes, scientists reported on Wednesday.

Magma from a Chilean volcano shot through Earth's crust at around a metre (3.25 feet) per second, a speed highlighting the perils from so-called rhyolitic volcanoes, scientists reported on Wednesday.

Volcanoes in this category provide some of Earth's most explosive events.

They are characterised by a dome of hardened magma which covers their central vent and can blow with catastrophic force, often with scant warning.

They include , Krakatoa and Mount St. Helens -- names that have gone down in history for inflicting loss of life and massive damage.

In the case of the Chaiten , in Chile's northern Patagonia, local residents at a town 10 kilometres (six miles) from the cone felt earthquakes at about 8 pm on April 30, 2008 that were powerful enough to knock objects off shelves.

The following day, the volcano erupted. On May 2, the volcano's lid, a caldera, was ripped off in a mighty blast.

Further eruptions continued for a week, distributing a blanket of ash in a wide swathe near the volcano.

Jonathan Castro of France's National Centre for Scientific Research (CNRS) and Donald Dingwell, of the Ludwig Maximilian University in Munich, Germany, collected ash samples and analysed crystals that are formed under specific conditions of pressure, temperature and water content.

They calculate that the magma took just four hours to ascend from a depth of more than five kilometres (three miles).

The surged upwards in the range of one metre (3.25 feet) per second before dispersing in an "explosive fragmentation" when it reached the surface.

"This result has implications for hazard mitigation because the rapidity of ascending rhyolite means that future eruptions may provide little warning," they write in the British .

The pair call for rhyolitic volcanoes that have not erupted since the last Ice Age, around 10,000 years ago, to be monitored.

"In more densely populated regions this would be essential to avoid a major volcanic disaster," they say.

(c) 2009 AFP

Explore further: Lightning plus volcanic ash make glass

add to favorites email to friend print save as pdf

Related Stories

New trigger found for volcanic eruptions

Sep 06, 2006

New insights into what might trigger the eruption of Mount St Helens and other potentially explosive volcanoes are reported today in Nature by scientists working at the University of Bristol, UK.

USGS to help Chile develop volcano early warning system

Jun 25, 2008

The U.S. Geological Survey is partnering with the Chilean government to develop a volcano early warning and emergency response system for the country after the historic eruption of Chaitén Volcano on May 2.

Bulge in Central Oregon may be a volcano

Sep 14, 2005

Scientists studying a land bulge near Bend, Ore., think a new volcano may be forming. A group from the U.S. Geological Survey is studying the swelling in Earth's crust. It is nearly two-thirds the size of Portland, Ore. ...

Recommended for you

Lightning plus volcanic ash make glass

21 hours ago

In their open-access paper for Geology, Kimberly Genareau and colleagues propose, for the first time, a mechanism for the generation of glass spherules in geologic deposits through the occurrence of volcan ...

A new level of earthquake understanding

Mar 03, 2015

As everyone who lives in the San Francisco Bay Area knows, the Earth moves under our feet. But what about the stresses that cause earthquakes? How much is known about them? Until now, our understanding of ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.