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Rock Doc: A step forward in predicting volcanic eruptions

By E. Kirsten Peters, College of Agricultural, Human & Natural Resource Sciences

Peters-e-k-2010-80PULLMAN, Wash. – There are two main things most people would like to know about particular volcanoes: when is the next eruption and how big will it be? Scientists in Iceland have taken a step forward in monitoring volcanoes to best predict when they will erupt and the size of the eruptions.

In May 2011, a volcano in Iceland named Grímsvötn erupted. It generated a 12-mile-high plume of volcanic debris that temporarily grounded airplanes as far away as Great Britain.

The problem wasn’t as great, though, as one that occurred a year earlier when another Icelandic volcano erupted. The 2010 eruption – from the Eyjafjallajökull volcano – grounded many flights across northern Europe and made major headlines at the time.

Info from GPS measurements

The 2011 Grímsvötn eruption was recently written about in the journal Nature Geoscience to illustrate a research advance that may help with predictions of volcanic activity. Because scientists knew the volcano was coming to life, they had placed a global positioning system (GPS) monitor on its flank.

About an hour before Grímsvötn erupted, the GPS device – rigged to send readings to scientists in real time – registered ground movement of a couple of feet.

Data from a GPS site “can tell you not only that there’s unrest at a volcano, but that it’s about to erupt and then how high its plume will be,” said Sigrún Hreinsdóttir, speaking to Nature Geoscience. Hreinsdóttir is a geophysicist at the University of Iceland and one of the authors of the journal article.

Ice sheet in the way

Obviously, the more information known, the better, when it comes to eruptions. Any information about timing can help people evacuate areas likely to be affected. And knowing how high the volcanic plume may reach can help pilots and air traffic controllers as they try to adapt to a rapidly unfolding situation.

Grímsvötn is a truly active volcano, so inquiring minds may want to know why it’s not thoroughly covered in GPS monitors. The answer is that much of the volcano lies beneath an ice sheet.

Ice sheets have their own movement issues, so monitoring them won’t give you good information about a volcano. Researchers did what they could to attach a GPS device on a rare, rocky outcrop above the ice.

Checking work with next eruption

Next came a bit of math. The researchers didn’t want to just record ground movement; they wanted to estimate what they could about what such movement meant for changes in pressure in the underground magma chamber. Such pressure tends to correspond to the size of the eventual ash plume.

It’s long been the case that seismic instruments have been used to monitor tremors and give general predictions of when an eruption will occur. But the GPS measurements have the advantage of giving information about the size of the eruption to come, Hreinsdóttir explained.

The new GPS approach with the magma-pressure calculations needs further testing.

“We need another eruption to prove we are right,” Hreinsdóttir said.

 

Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.

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