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GPS Data, Satellite Images Used to Study Icelandic Caldera

June 1, 2015  - By

This Landsat 8 image, Caltech acquired on Sept. 6, 2014, is a false-color view of the Holuhraun lava field north of Vatnajökull glacier in Iceland. The Bárðarbunga caldera is visible in the lower left of the image under the ice cap.
Photo: U.S. Geological Survey / Caltech

Access to satellite images and GPS data has allowed scientists to document the collapse of the Bárðarbunga caldera, a volcano beneath the Vatnajökull ice cap in Reykjavik, Iceland.

Mark Simons, a professor of geophysics at the California Institute of Technology (Caltech), traveled to Reykjavik with 15 students and two faculty members on Aug. 16, 2014, to lead a tour of the volcanic, tectonic, and glaciological highlights of Iceland. That day, earthquakes occurred  — the seismicity was related to the Bárðarbunga caldera.

Simons is one of the leaders of a Caltech and Jet Propulsion Laboratory (JPL) project known as the Advanced Rapid Imaging and Analysis (ARIA) program, which aims to use a growing constellation of international imaging radar satellites that will improve situational awareness and response following natural disasters, according to Caltech. Under the ARIA umbrella, Caltech and JPOL, managed for NASA by Caltech, had formed a collaboration with the Italian Space Agency (ASI) to use its COSMO-SkyMed (CSK) constellation — consisting of four orbiting X-Band radar satellites — following such events.

CSK used an interferometric synthetic aperture radar (InSAR) technique to gather images of the surface of the glacier above the caldera. By the evening of Aug. 28, Caltech says the first interferogram showed that the ice above the caldera was subsiding at a rate of 19.685 inches a day.

Simons took the data to researchers at the University of Iceland who were tracking Bárðarbunga’s activity on Aug. 29.

“At that point, there had been no recognition that the caldera was collapsing. Naturally, they were focused on the dyke and all the earthquakes to the north,” Simons said. “Our goal was just to let them know about the activity at the caldera because we were really worried about the possibility of triggering a subglacial melt event that would generate a catastrophic flood.”

The flood never occurred, but Caltech says the researchers at the University of Iceland increased their observations of the caldera with radar altimetry flights and installed a continuous GPS station on the ice overlying the center of the caldera.

The Icelandic researchers published a paper in December 2014 in Nature about the Bárðarbunga event, largely focusing on the dyke and eruption. Simons and his colleagues have developed a model to describe the collapsing caldera and the earthquakes produced by that action. The new findings appear in the Geophysical Journal International.

Bryan Riel, a graduate student in Simons’s group and lead author on the paper, used the interferogram of the Bárðarbunga area, along with four others collected by CSK in September and October, to show that the earthquakes were not the primary cause of the surface deformation inferred from the satellite radar data.

“What we know for sure is that the magma chamber was deflating as the magma was feeding the dyke going northward,” Riel said in the article. “We have come up with two different models to explain what was actually generating the earthquakes.”

“Because we had access to these satellite images as well as GPS data, we have been able to produce two potential interpretations for the collapse of a caldera — a rare event that occurs maybe once every 50 to 100 years,” Simons said. “To be able to see this documented as it’s happening is truly phenomenal.”

About the Author: Joelle Harms

Joelle Harms is the digital media manager for GPS World. Harms completed her undergraduate degree at Ohio University where she earned a Bachelor of Science in Journalism and creative writing specialization from the E.W. Scripps School of Journalism. She specifically creates content for GPS World and Geospatial Solutions digital properties including newsletters, videos, social media and websites.