NASHVILLE, Tenn. (WHTM) – A lot of middle Tennessee residents have called police, news stations and even 911 after hearing what they describe as loud booms or explosions in the middle of the night.
Some thought the booms were gun shots or exploding transformers, but there’s a scientific explanation.
WKRN-TV reports the residents are encountering a mysterious weather phenomenon called cryoseism.
Cryoseismic booms, or frost quakes, are caused when frozen water expands quickly in the ground, according to the National Weather Service.
When water runs into the ground and freezes, it expands when the temperature drops dramatically, putting stress on the surrounding soil or rock. The pressure is released with a booming sound and slight tremor.
The National Weather Service said the activity is completely harmless.
Cryoseism typically occurs in the Northeastern United States and Canada.