New research into an Icelandic eruption has shed light on how the Earth’s crust forms, according to a paper published today in Nature. When the Bárðarbunga volcano, which is buried beneath Iceland’s Vatnajökull ice cap, reawakened in August 2014, scientists had a rare opportunity to monitor how the magma flowed through cracks in the rock away from the volcano.
New research into an Icelandic eruption has shed light on how the Earth’s crust forms, according to a paper published today in Nature.
When the Bárðarbunga volcano, which is buried beneath Iceland’s Vatnajökull ice cap, reawakened in August 2014, scientists had a rare opportunity to monitor how the magma flowed through cracks in the rock away from the volcano.
The molten rock forms vertical sheet-like features known as dykes, which force the surrounding rock apart.
Study co-author Professor Andy Hooper from the Centre for Observation and Modelling of Earthquakes, volcanoes and Tectonics (COMET) at the University of Leeds explained: “New crust forms where two tectonic plates are moving away from each other. Mostly this happens beneath the oceans, where it is difficult to observe.
“However, in Iceland this happens beneath dry land. The events leading to the eruption in August 2014 are the first time that such a rifting episode has occurred there and been observed with modern tools, like GPS and satellite radar.”
Although it has a long history of eruptions, Bárðarbunga has been increasingly restless since 2005. There was a particularly dynamic period in August and September this year, when more than 22,000 earthquakes were recorded in or around the volcano in just four weeks, due to stress being released as magma forced its way through the rock.
Using GPS and satellite measurements, the team were able to track the path of the magma for over 45km before it reached a point where it began to erupt, and continues to do so to this day. The rate of dyke propagation was variable and slowed as the magma reached natural barriers, which were overcome by the build-up of pressure, creating a new segment.
The dyke grows in segments, breaking through from one to the next by the build up of pressure. This explains how focused upwelling of magma under central volcanoes is effectively redistributed over large distances to create new upper crust at divergent plate boundaries, the authors conclude.
As well as the dyke, the team found ‘ice cauldrons’ – shallow depressions in the ice with circular crevasses, where the base of the glacier had been melted by magma. In addition, radar measurements showed that the ice inside Bárðarbunga’s crater had sunk by 16m, as the volcano floor collapsed.
Continue reading at the University of Leeds.
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