A "frost quake" happens when moisture in the ground suddenly freezes and expands. If conditions are just right, the soil or bedrock breaks like a brittle frozen pipe, generating mysterious noises that range from an earthquake-like rumble to sharp cracking sounds sometimes mistaken for falling trees.
This winter has been ripe for frost quakes, known technically as cryoseism. Temperatures have been frigid, but occasional warm-ups have allowed for thawing. And the temperature swings have sometimes been abrupt.
Damage is not common, but it happens. In Waupun, Wis., a frost quake last month created a 100-foot crack in a driveway. Homeowner Dennis Olssen told authorities the boom was so loud he thought it was an explosive until he learned that neighbors experienced the same thing.
VIDEO ABOUT THE FROST QUAKE IN TORONTO THIS WINTER (From Global Toronto):
FULL ABC NEWS ARTICLE: http://abcnews.go.com/US/wireStory/mysterious-noises-traced-rare-frost-quakes-22380996