TWO types of magma and very odd plumbing 鈥� that鈥檚 wot dunnit.
Iceland鈥檚 Eyjafjallaj枚kull volcano took the world by surprise when it erupted in April and brought European airspace to standstill. Now a study of earthquake recordings and satellite data on deformations in the mountain has explained the eruption.
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Most active volcanoes have a single chamber that fills with magma, then pops. Instead, Eyjafjallaj枚kull has a series of shallow horizontal chambers that lie parallel to each other, says Freysteinn Sigmundsson of the University of Iceland in Reykjavik. As magma rises, it forms new horizontal sheets. Some began to form over 18 years ago, and in March the magma started to trickle out of an opening on the flank of Eyjafjallaj枚kull (see graphic; Nature, ).
And that might have been it, had the fresh magma in one sheet not bumped into a different type of magma, possibly lingering from the last eruption, 200 years ago. 鈥淭he two had different compositions, temperatures and gas content and their meeting triggered the explosive eruption,鈥� says Sigmundsson.
