Chicago's minus temperatures – previously lower on Thursday than in Alaska and Antarctica – have reportedly triggered a loud, ground-shaking phenomenon: so-called "frostquakes."
Chicago WGN-9 reported that residents heard a "loud boom" Wednesday night when temperatures were well below zero.
POLAR VORTEX CREATES CHICAGO RIVER TO 'SMOKE', FREEZING AS SUBZERO TEMPERATURES
The event was probably caused by frostquakes – or "cryoseisms" as they are formally called, that occur when Water trapped underground suddenly freezes when the temperature drops and expands, "explained Live Science. As the water expands, pressure builds up under the water pressure
VIRAL PHOTO OF CHICAGO INMATES EXPANDING IN FREEZING THE WEATHER THAT Jail TELLS EXPLANATION OF DECLARATION
"It's more a noise phenomenon like a balloon blast than a physical hazard "Dave Call, a meteorologist at Ball State University, told Muncie Star Press of Frostquakes.
In some cases "rivets" have actually been observed After hearing the loud boom of a frostquake, "Popular Science" reported the phenomenon.
Although they may sound similar, frostquakes are not the same as earthquakes ̵