More weird weather in Chicago from the polar vortex

Extreme cold causes bizarre things to happen, and that was certainly the case Wednesday in Chicago when a series of loud booms were reported.

The temperature in Chicago dropped to 23 below zero early Wednesday, one of the coldest readings ever recorded in the city.

What Chicago residents heard were likely “frost quakes,” also known by the dull geological term “cryoseisms.”

They occur when a rapid drop in temperature leads to a quick freeze, which causes the rock or soil to burst rather than just slowly expand, according to meteorologist Keith Heidorn. The rapid bursting sounds like noisy quake, along with possible shaking. 

Some people think their homes are being broken into or gunshots are being fired.

Frost quakes are too small to be picked up by a seismograph, so they’re difficult to prove, geologist Jeri Jones of Jones Geological Services said last year. Jones said they only be heard about 300 feet away. 

Dave Call, a meteorologist at Ball State University, said to think of a bottle of liquid in a freezer, expanding and exploding. “It’s more of a noise phenomenon, like a balloon popping, than a physical danger,” Call said earlier this month.

He compared frost quakes to the familiar phenomenon of potholes: Water seeps into cracks in the pavement, freezes and expands.

“I thought I was crazy!” Chastity Clark Baker said on Facebook, according to WGN. “I was up all night because I kept hearing it. I was scared and thought it was the furnace.”

Unfortunately, frost quake damage normally is not covered by a homeowners insurance policy. 

Folks in Chicago, and elsewhere in the Midwest, soon won’t have to worry about frost quakes as temperatures soar into the 30s and 40s by the weekend. 

Contributing: Abbey Zelko, the York (Pa.) Daily Record; Seth Slabaugh, the Muncie (Ind.) Star Press

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