|Image Source: AccuWeather.com|
It might be cold enough in Chicago right now to make the ground shake.
Local news station WGN reported today (Jan. 30) that its viewers had heard "frost quakes" in the city overnight. And though the reports in Chicago are still unconfirmed, frost quakes are indeed a real thing.
Frost quakes, or "cryoseisms," occur when water trapped underground freezes suddenly as the temperature drops, causing it to expand. (Water expands as it freezes.) All that rapidly expanding water underground can split rocks and put stress on the soil, causing loud booms. Frost quakes are fairly rare events and difficult to positively identify. A huge blast that shook northwest Calgary, Canada, in 2014 was widely attributed to a loud cryoseism, but researchers never confirmed that as the cause.
For a frost quake to occur, at least three conditions are required, according to "Frost Quakes: Forecasting the Unanticipated Clatter," published online in 2015 in the meteorology journal Weatherwise. First, rain or snowmelt saturates the ground with water. Second, there's little to no snow on the ground, which otherwise blankets the soil and protects it from sudden temperature changes. Third, the temperature rapidly drops, freezing the earth.
The Polar Vortex Might Be Causing 'Frost Quakes' in Chicago, Rafi Letzter, Live Science