December 17, 2014
Icelandic volcano leads to new insight into Earth’s crust formation
Chuck Bednar for redOrbit.com - Your Universe Online
An in-depth analysis of the August 2014 volcanic eruption in Iceland has shown that a new layer of the Earth’s crust is forming beneath the lava-spewing rupture, according to new research published online Monday in the journal Nature.Professor Andy Hooper of the Centre for Observation and Modelling of Earthquakes, volcanoes and Tectonics (COMET) at the University of Leeds and his colleagues made the discovery while studying the Bárðarbunga volcano, gaining new insight into how crust forms in the process.
The eruption, which gave them a rare chance to monitor magma flowing through cracks in the rock away from the volcano, which is buried beneath Iceland’s Vatnajökull ice cap. The molten rock formed dykes, or vertical sheet-like features which force the surrounding rock apart.
“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,” Hooper explained in a statement. “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.”
While Bárðarbunga has a long history of eruptions, the researchers said that it has become increasingly active since 2005, and went through an especially dynamic period this past August and September. During a four-week period, over 22,000 earthquakes were recorded in or around the volcano due to stress being released as magma forced its way through the rock.
The volcano’s activity gave Hooper and his fellow researchers to observe a dyke as it formed using satellite imagery and GPS measurements, according to The Verge. The study authors said that they were able to track the magma’s path for approximately 28 miles (45 kilometers) before it reached the point where it began to erupt, which it continues to do to this very day.
They found that the rate of dyke propagation was variable, slowing as the magma reached natural barriers. It managed to overcome those barriers, however, by building up pressure and creating a new segment. This explains how focused upwelling of magma underneath a volcano winds up being redistributed over large areas to create new upper crust at divergent plate boundaries.
“Our observations of this event showed that the magma injected into the crust took an incredibly roundabout path and proceeded in fits and starts,” Professor Hooper said, according to Nature World News. “Initially we were surprised at this complexity, but it turns out we can explain all the twists and turns with a relatively simple model, which considers just the pressure of rock and ice above, and the pull exerted by the plates moving apart.”
Furthermore, he and his co-authors discovered shallow depressions in the ice cap with circular crevasses. These so-called ice cauldrons were where magma had melted the base of the glacier, they explained. Radar measurements also revealed that the ice within Bárðarbunga’s crater had sunk by roughly 52 feet (16 meters) as the floor of the volcano started to collapse.
“Using radar measurements from space, we can form an image of caldera movement occurring in one day,” said study co-author and COMET PhD student Karsten Spaans. “Usually we expect to see just noise in the image, but we were amazed to see up to 55cm of subsidence.”