Glaciers and Earthquakes: What Happens When They Shake

When a glacier breaks apart in an enormous calving event, this is part of a "glacial quake" that can be picked up on seismic instruments around the world. These events have been increasing in number in recent years, according to a release.

Scientist Tavi Murray and colleagues at Columbia University, Swansea University, Newcastle University, and others wanted to find out what was happening when the earth shakes like this, according to a release.

They have released a report published by the journal Science, in which they say that when a giant iceberg falls over with enough force, it pushes back on the glacier, making the glacier move backward and downward for several minutes, as Science Daily said.

"Imagine that you could go and just push on the front of the glacier with your thumb, really hard, so hard that you could reverse the direction that the front of the glacier is moving," researcher Meredith Nettles, of Columbia University, told NPR. "And then you let it go. And that backward and then forward motion is actually recorded in the GPS data from the front of the glacier."

The scientists conducted their research on Greenland's Helheim Glacier, using cameras, GPS sensors, and the global seismographic network, for 55 days in 2013, according to a release.

During that time, the glacier retreated about a mile, and researchers captured details of ten large-scale calving events. They saw how the icebergs fell away from the glacier and temporarily reversed its course, causing glacial earthquakes that measure about magnitude five on the Richter Scale, according to a release.

Read about accelerating glaciers here. https://currents.ucsc.edu/05-06/11-14/glacier.asp