Months of volcanic restlessness preceded the eruptions this spring of Icelandic volcano Eyjafjallajökull, providing insight into what roused it from its centuries of slumber. An international team of researchers analyzed geophysical changes in the dormant volcano leading up to its eruptions in March and April 2010. Scientists suggest that magma flowing beneath the volcano may have triggered its reawakening.

Lead study author Freysteinn Sigmundsson at the University of Iceland, Kurt Feigl, professor of geoscience at the University of Wisconsin-Madison, and collaborators from Iceland, Sweden, and the Netherlands watched the deformation of the volcano’s edifice using a combination of satellite imaging and GPS surveying. They found that Eyjafjallajökull swelled for 11 weeks before it began to erupt in March 2010 from one flank, a culmination of 18 yrs of intermittent unrest.

In late summer 2009, a subtle shift at a GPS station on the volcano’s flank prompted Sigmundsson and his colleagues to begin monitoring the mountain more closely. In early January 2010, the rate of deformation and the number of earthquakes began to increase. As the deformation and seismic unrest continued, the researchers installed more GPS stations near the mountain. The instruments detected more rapid inflation, indicating that magma was moving upwards through the “plumbing” inside the volcano.

By the time the volcano began to erupt on March 20, 2010, the volcano’s flanks had expanded by more than 6 in. as magma intruded into a series of underground structures called dikes and sills. Although many volcanoes deflate as magma flows out of shallow chambers during an eruption, Eyjafjallajökull maintained the same inflated shape through mid-April, when the first eruption ended.

After a two-day pause, the volcano began to erupt again on April 22nd. The lava broke through a new vent under the ice-capped summit of the mountain. This second eruption exploded as gas escaped from bubbles in the magma, fragmenting the rock into tiny particles called “tephra.” Aggravating the explosion, steam blew out of the vent as hot lava melted a pathway through the ice in a matter of days. The resulting plume rose high into the atmosphere, disrupting air traffic over Europe for weeks and stranding millions of travelers.

Why did Eyjafjallajökull erupt when it did? The scientists suggest that magmatic intrusions deep within the volcano started the processes leading to the eruption. “It was the meeting of two different magma types, one residing under the summit area, and another in the evolving intrusion, that triggered the explosive eruption,” said Sigmundsson.

The researchers are also currently studying the structures inside the volcano, such as magma chambers and intrusive conduits, by extracting information from the sensors installed around Eyjafjallajökull.

Illustration of the 3D geometry (left) and timing of events (right column) at Eyjafjallajökull volcano. The first three panels in the time series show distinct intrusive episodes of magma that caused measurable deformation and seismic events in 1994, 1999, and in the first several months of 2010. The fourth panel illustrates the first eruption, between March 20 and April 12, 2010, when basaltic magma (red) erupted onto the Earth’s surface on the flank of the mountain. The fifth panel shows the  second eruption, between April 14 and May 22, when a different type of magma (trachyandesite, shown in orange), erupted explosively under the ice-capped summit.

Satellite radar images were obtained from TerraSAR-X, a satellite operated by the German Space Agency (DLR). Funding was provided by a RAPID grant from the U.S. National Science Foundation, the Icelandic Research Fund, the University of Iceland, and the Icelandic government.

National Science Foundation
www.nsf.gov

::Design World::

---

Filed Under: Green engineering

 

---