Iceland Volcano Proving Tough to Predict
Posted by
Target on 4/26/2010, 2:04 am
from http://news.sciencemag.org
by Richard A. Kerr on April 19, 2010 5:12 PM
'Silica-rich magma makes for more viscous-and thus more explosive-lavas and can be produced as some minerals crystallize out of subterranean magma. '
'Eyjafjallajokull is not divulging its longer-term intentions either. According to geophysicist Pall Einarsson of the University of Iceland, the magma feeding the current eruption seems to be coming from down deep rather than a shallow chamber. So it is impossible to gauge just how much magma could emerge during this episode of activity.'
'The best clues may come from the historical record. That isn't encouraging, according to volcanologist Lee Siebert, director of the Global Volcanism Program at the Smithsonian Institution in Washington, D.C. Ominously, three of the previous four eruptions at Eyjafjallajokull have been accompanied by eruptions at its neighbor Katla, according to Siebert's reading of the literature. '
'Eyjafjallajokull's most recent eruption, in 1821, rated a moderate two on the logarithmic volcanic explosivity index. This index runs from a nonexplosive zero to an eight; Mount St. Helens was a five. But Katla has produced 208 ash layers in the past 8400 years, some eruptions rating a four or even a five. Icelanders have a close eye on Katla, Einarsson says, but no sign of stirrings yet.'
http://news.sciencemag.org/sciencenow/2010/04/icelands-volcano-proving-tough-t.html |
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