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Iceland's Volcano Exposes How Calderas Are Really Form

Nearly two years ago, Europe experienced its biggest volcanic explosion for 240 years. Now, a present study of the volcanic explosion has provided extraordinary information about the development of calderas, the unwell understood arrangements some volcanic outbreaks leave behind.

The Bardarbunga eruption in fact released 10 times as much volcanic solid, up to two cubic km (half a cubic mile),as its more prominent predecessor.

A team of researchers led by Professor Magnus Gudmundsson of the University of Iceland has described the process that created the caldera in the journal Science. Calderas form when a magma lake inside a volcano evacuates. Material directly above it collapses, leaving a dejection that in some cases fills and turns into a lake. Calderas have been seen on other moons and planets and can be the size of big cities. Only six have formed ever since 1900, and since it is not precisely safe to watch their formation close by, there is still much more about them we do not know, counting the problem, which is whether the collapse causes the lake to empty, or vice versa. According to Gudmundsson, Bardarbunga's magma lake lay 12 km (7.5 miles) under the surface. Instead of being forced to go straight up, the magma gets through a wall in its comprising dike, rolling beneath the Earth for 45 km (28 miles) until it found a room where it could come to the surface. The settling of the rock layer has been caused 77 earthquakes of magnitude 5 and beyond. The team's explanations indicate that the magma's escape led the caldera's formation, rather than being caused by it, but only one example is not enough to determine if this is each time the case.

What Bardarbunga was doing directly above the surface was nothing related to what was happening underneath the ground. Peter Hartree via Wikimedia Commons. cc-by-sa-2.0

Ending the course of six months, an already deep ball, 11 km (7 miles) at its widest size, sunk 65 m (213 feet). The ground initially sank 1 m (3.3 feet) a day, reducing through the 181 days the outbreak continued.

Co-author Dr.Eoghan Holohan, of the GFZ German Research Center for Geosciences, said in a statement, "With an area of 110 square km (42 square miles), this is the biggest caldera collapse ever examined. The results provide the indistinct picture yet of the start and evolution of this puzzling geological process."

The authors traced the magma's course by detecting distortions in seismic waves passing over the Earth. They detected that the river of escaping magma from the volcano’s cavity was an impressively consistent system: Surprises either at the cavity or where magma touched the surface spread all the way to the other end of the lava flow.

Living up to Iceland's reputation as the unique land of ice and fire, the Bardarbunga caldera lies underneath the Vatnajokull glacier, Europe's biggest, causing the caldera to fill with ice. Co-author Dr.Thomas Walter, of the GFZ, said, "The incident was a blessing in disguise as the outbreak could have happened right beneath the ice. In that situation, we'd have had a water vapor explosion with a volcanic ash cloud even greater and longer lasting than the one that monitored the outbreak of Eyjafjallajokull in 2010."

The work's journal was part of a different issue in Science on natural risks. By the values of other observed caldera developments, Bardabunga was remarkably shallow. Whereas covering a bigger area than any we have previously observed in formation, it is small compared to super-volcanoes such as those at Yellowstone.

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