But not Eyjafjallajökull.
The Icelandic volcano stirred in March and grounded European air travel has a peculiar kind of plumbing, scientists report in Nature. Freysteinn Sigmundsson and colleagues combined 20 years' worth of GPS, satellite, and seismic observations of the volcano see note how it changed over the years-and especially what was happening in the lead-up to this year's eruption.
"One of the surprises was the complexity of the plumbing system," Sigmundsson said. "There was not one main magma chamber active under the volcano capturing magma in 18 years of unrest preceding the eruption, as is often envisioned in models for the most active volcanoes on Earth. Rather, two or more discrete magmatic sources were involved, with magma of different composition."
The cause of Eyjafjallajökull's explosive eruption seemed to be the meeting of one body of magma, made up mostly of the common volcanic rock basalt, with another type of magma within the volcano, consisting largely of silica-rich trachyandesite," he said in an interview with MSNBC.
In January-two months prior to eruption-Eyjafjallajökull began to come to life with small earthquakes in the area and expansion of the mountain. Eventually, the sides of the volcano bulged by more than 15 centimetres (six inches) before the first eruption began on March 20. It took almost a month for the volcano to start to deflate, which is a surprise given that volcanoes "shrink," rather like a poorly-knotted balloon, as molten rock and scorching gases flow from the chamber.
This volcano's weird personality could help vulcanologists figure out the dynamic process happening in other magma chambers, says coauthor Kurt Feigl. He told the Guardian: "The explosiveness of the eruption depends on the type of magma, and the type of magma depends on the depth of its source. We're a long way from being able to predict eruptions. But if we can visualise the magma as it moves upward inside the volcano, then we will improve our understanding of the processes driving volcanic activity."
By Andrew Moseman
Reprinted with permission from Discover