by Caleb, KE0FOE
Also known as cryoseisms, frost quakes are non-tectonic seismic events. This means they’re not caused by the shifting of the Earth’s tectonic plates. Frost quakes are caused by a sudden rapid freezing of ground and bedrock, usually when temperatures quickly go from above freezing to below zero. As moisture absorbed in the rock and soil freezes, it expands. This puts a great amount of stress on the areas around it. Eventually, the stress is too much and the soil and rock will crack in an “explosive” manner, creating a loud sound and even shaking the ground surface. Since temperatures are coldest in the overnight hours, most people experience frost quakes in the middle of the night.
More information about Frost Quakes can be found on Wikipedia: https://en.wikipedia.org/wiki/Cryoseism