MADISON, WI. (THECOUNT) — Residents of Madison, Wisconsin reported hearing a series of loud booms Thursday.

The “sudden explosive sounds,” that were enough to make some Madison residents jump out of bed, are called Ice quakes, aka, frost quakes, occurring when water in the ground freezes and expands, according to officials.

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The expansion of ice can create very loud, frequent pops and crackles, say officials. But there’s no need to be alarmed; the booms, although noisy, are basically harmless.

Did you hear a loud ‘boom’ today?! We’re actually getting several reports around the area… and there’s nothing to fear! Those pops and booms are called ice quakes; they’re caused by the water in the ground freezing & expanding, source Channel3000

Reports of ice quakes are very common in the northern Midwest after large drops in temperature.

Geo facts: Madison, the capital city of Wisconsin, lies west of Milwaukee. It’s known for the domed Wisconsin State Capitol, which sits on an isthmus between lakes Mendota and Monona. The Wisconsin Historical Museum documents the state’s immigrant and farming history. The city’s paved Capital City State Trail runs past Monona Terrace, a lakefront convention center designed by Frank Lloyd Wright – wikipedia.