U Chicago Team Discovers Millions Of "Icequakes" On Ross Ice Shelf When Melt Freezes At Night

[hatrack]

The icy continent’s enigmatic earthquakes have begun to come under far closer scientific scrutiny as of late. East Antarctica, for example, was long assumed to be lacking in earthquakes – strange, considering that it’s undergoing prolonged extension by tectonic forces, which should be activating plenty of faults. As it happens, research released last summer found that the apparent aseismicity was down to a data bias: there simply weren’t enough seismic stations on Antarctica before 2007, and when they were set up, dozens of quakes were detected.

Ice quakes are not exactly a new idea, but as before, little was known about their presence and triggering mechanisms simply because we didn't have the instrumentation in place. Seismometers may have once again come to our rescue, but this time around, they aren't picking up on bona fide tectonic tremblors.

Ice quakes, despite the name, aren’t really earthquakes. They might be releasing seismic waves that can be picked up by seismometers, but make no mistake, there are no tectonic forces at work here causing ice to snap on this scale. In fact, these ice quakes are perhaps more related to those frost quakes, or cryoseisms, that were being picked up in Chicago during the recent onslaught of the polar vortex. As wet soil freezes over, the water within it expands and, coming up against the earth around it, can suddenly snap, creating very localized tremors.

EDIT

To wit, the researchers set up a seismometer array on the McMurdo Ice Shelf in Antarctica during a recent summer, from November 2016 to January 2017. Near a slush-filled, prone-to-melting part of the shelf, they detected millions of small ice quakes during that time. The fact that these quakes only seemed to take place during a 6-to-12-hour period in the evening, and that they didn’t take place in areas of dry ice, betrayed their origin: the interaction of multiple ice layers during a diurnal thaw-freezing cycle was the only sensible explanation here. A simple computer model, which simulated the daily transfer of heat to and from the surface ice, confirmed their suspicions.

EDIT

https://www.forbes.com/sites/robinandrews/2019/02/28/thousands-of-quakes-rock-antarcticas-ice-shelves-at-night-heres-why/#825544f233ae

[littlemissmartypants]

1. aseismicity, cryoseisms

I love language and DU, especially when they both collide. Interesting post. Thanks hatrack.