Watching volcanoes deflate aids ash forecast

Two hours into Grímsvötn's May 2011 eruption.

Björn Oddsson

Nobody likes being stuck in an airport by a cascade of cancelled flights, uncertainly adrift in the vagaries of rescheduling. These circumstances are usually brought about by lousy weather, as many travelers in the US were reminded over the holidays. But that’s not the only monkey wrench in Mother Nature’s bag of tricks.

Erupting volcanoes can hurl up huge clouds of ash made of microscopic particles of volcanic glass, a situation that creates a serious risk for airplane engines. Eruptions of Iceland’s Eyjafjallajökull in 2010 and Grímsvötn in 2011 each wreaked havoc on the air travel system as flights were diverted around their ash clouds. A group of researchers led by Sigrún Hreinsdóttir studied data collected during the Grímsvötn eruption, and they think they may have discovered something that could help: a way to improve forecasts of how that dangerous plume of ash will change over time.

The volcanic mouth of Grímsvötn sits beneath an ice cap, with only one point of rock along its rim piercing the glacial mantle. A very precise GPS station and a device that measures tilting sit on that point to help monitor the volcano’s behavior. Volcanoes like Grímsvötn actually swell a bit while the magma chamber fills and pressurizes—until the pressure is so great that they erupt.