ice
February 20, 2015

Tennessee explosions are just tiny frost-quakes

Chuck Bednar for redOrbit.com - @BednarChuck

If you’re one of the Tennessee residents that has been awakened by loud explosions recently, you have an unusual weather phenomenon known as cryoseisms to thank for your lack of sleep.

What is a cryoseism?

According to WKRN News in Nashville, several people living in middle Tennessee have heard what they describe as “loud booms” or “explosions” in the middle of the night. Some have called the local news or even 911 believing that they might be gun shots or transformers exploding, but as it turns out, there’s actually a scientific explanation for the phenomenon.

A cryoseism, also known as an ice quake or a frost quake, is described by the Maine Geological Survey as a natural phenomenon which produces ground shaking and noises similar to those of an earthquake. They are caused by sudden deep freezing of the ground, which usually occurs when temperatures quickly fall from above freezing to below zero.

Frost quakes are most common when there is no snowfall to help insulate the ground, and they are unique in that they are localized events, the agency noted. They release vibrations that sometimes travel distances of a few hundred yards.

Tiny frigid earthquakes

They don’t release as much energy as earthquakes, but they can generate a significant impact right at the site – enough to jar people awake. Cryoseisms typically occur during the coldest part of the night (between midnight and dawn), and under the right conditions they can occur over several hours or even on successive nights.

[STORY:  Methane Release From Earthquakes Feeds Global Warming]

As the Associated Press reported last February, damage resulting from frost quakes is rare, but experts advise anyone who has experienced one to check their homes for damage to water or gas lines, as well as cracks in the foundation in their homes. In January 2014, a cryoseism created a 100-food crack in the driveway of one Wisconsin homeowner, the wire service added.

The National Weather Service told WKRN news that cryoseismic booms are usually caused by the quick expansion of frozen water within the surface. When groundwater freezes, it expands and puts added stress on the surrounding rock or soil. The explosive sounds are the result of the built-up pressure being released.

[STORY: Looking At Snow Depth With NASA Data]

A 1979 study from the University of Wisconsin–Milwaukee Department of Geological Sciences reported that cryoseisms typically occur three to four hours after a significant cooling event, and that following a large frost quake, little to no seismic activity will be detected for several hours, indicating that the accumulated stress from the temperature change has been relieved.

The Tennessee news outlet said that it had received reports of frost quakes from Ashland City, Hermitage, Hohenwald, Nolensville and other locations in the middle part of the state. Officials from the Maine Geological Survey said that there have previously been reports of such incidents in upstate New York, Vermont, Massachusetts, Connecticut, and Maine.

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