Saturday, October 17, 2009

Rhyolitic volcanoes

Rhyolitic volcanoes: the ones to watch in Nature.
The Chaitén volcano in Chile erupted unexpectedly and explosively on 1 May 2008, and it is still erupting. The eruption has displaced over 5,000 people, and resulted in millions of dollars of lost revenue in Chile. It has also provided geophysicists the rare opportunity of directly observing a rhyolite magma fuelled eruption — the cause of some of Earth's largest explosive volcanic eruptions. Jonathan Castro and Donald Dingwell present petrological and experimental evidence to show that the hydrous rhyolite magma at Chaitén ascended very rapidly, with velocities of the order of a metre per second. Such rapid ascent, contrasting markedly with the behaviour of most silicic magmas, implies a transit time from storage depths greater than 5 km to the near surface of only 4 hours, leaving little warning time for such eruptions. This work suggests that rhyolitic volcanoes that have been active during the Holocene — the past 10,000 years or so — should be closely monitored, especially those near major centres of population.

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