Everyone has heard of the “sonic boom.”  You know, the sound created when an object traveling through the air faster than the speed of sound breaks the sound barrier sending shockwaves through the air?

Now have you ever heard of a “cold boom”?  Technically known as a cryoseismic boom, this phenomenon is reserved only for the coldest of temperatures, and considered pretty rare for the lower latitudes of the continental United States.  The boom sound is created by a cryoseism, which is a mini explosion within the ground caused by the rapid expansion of frozen water.

This cool phenomenon shocked the Upper Midwest last weekend, and more recently parts of Canada including Toronto over the weekend, when temperatures crashed with the arrival of arctic cold fronts rapidly freezing any water and moisture underground.  A quick search for “strange booms” on Twitter revealed these cryoseisms have been heard from Green Bay, to Chicago, to Toronto in the past week.

While considered harmless, these cryoseismic booms certainly caused a stir waking several people from their slumber.

So next time you hear a loud boom during a cold outbreak, it was likely a rare cryoseismic “cold boom!”

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