“Residents in the frigid Midwest have been startled during the polar vortex by shuddering booms.

“They weren’t gunshots. They weren’t explosions. It appears, they may have been frost quakes, better known to weather geeks as cryoseisms—a deep-freeze phenomenon that even the scientist who coined the term has trouble explaining.

““What we believe is happening is when there is a significant plunge in the air temperature and the saturated soil cools quickly, the ice in the ground can expand rapidly enough to create a loud boom noise at the surface,” geologist Steven Battaglia told the Daily Beast.”

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