November 18, 2010

‘Geologic Unrest’ Preceded Icelandic Volcano Eruptions

The eruption of the Icelandic volcano Eyjafjoell earlier this year followed a long, threatening warming period in which the volcano rumbled and bulged, scientists reported on Wednesday.

Vulcanologists from the US, Iceland, Sweden and the Netherlands studied satellite images and checked data from GPS movement monitors to construct a gradual representation of events.

"Several months of unrest preceded the eruptions, with magma moving around downstairs in the plumbing and making noise in the form of earthquakes," Kurt Feigl, a professor of geosciences at the University of Wisconsin at Madison, said in a statement.

The eruption of the volcano ejected a cloud of ash which affected more than 100,000 flights and millions of passengers.

The vulcanologists, reporting in the British journal Nature, said they stepped up observations of the volcano in mid-2009, when a GPS station on the southern side of Eyjafjoell suddenly showed movement of close to half an inch.

The volcano was experiencing several seismic episodes daily by January 2010, signaling the inflow of magma into its roots. Eventually, the volcano's sides bulged out by more than 6 inches before the first eruption on March 20.

It took nearly a month for the volcano to start to deflate, which surprised scientists, given that volcanoes usually "shrink" as molten rock and scorching gases flow from the chamber.

A second eruption occurred on April 14, in which lava broke through a channel under the ice on the mountain's summit causing an "explosive" reaction as water flashed to steam and gas escaped from bubbles in the magma.

The result was a cloud of ash that rose into the sky up to 30,000 feet and causing misery for millions of stranded air travelers.

Scientists were unsure why the volcano erupted when it did. One reason could have been that magma intruded into the volcano's heart through a network of conduits and chambers.

"The explosiveness of the eruption depends on the type of magma, and the type of magma depends on the depth of its sources," Feigl said.

"We're a long way from being able to predict eruptions, but if we can visualize the magma as it moves upward inside the volcano, then we'll improve understanding of the processes driving volcanic activity," he concluded.


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