Frost quakes, formally known as cryoseisms, are weather-related seismic events caused by the sudden cracking of frozen earth or rock, which has been saturated with water that turned into ice.
These quakes occur when water drains into the ground, freezes, and then expands rapidly when temperatures drop below freezing, causing the ground to crack and create mini-explosive sounds
Frost quakes need certain conditions to happen: significant rainfall, little snow cover, and a sufficient amount of water that can be affected deep underground by rapidly changing temperatures
A significant snow cover, as little as six inches, can act as an insulator for the ground, preventing the rapid freezing of water beneath the surface, thus inhibiting frost quakes
They can be loud enough to wake people from sleep or cause shock, but are generally not dangerous like earthquakes. The vibrations caused by frost quakes are usually not felt above ground
Unlike earthquakes, frost quakes are not related to the shifting of tectonic plates or rising magma. They are purely a result of weather conditions
While they can crack the ground and occasionally cause fissures to roads and sidewalks, frost quakes are rarely severe enough to cause harm or endanger safety
Frost quakes are instantaneous and hard to predict. They occur without warning but are generally harmless
The recent occurrence in Chicago was likely due to a rapid temperature drop following a period of melting snow, creating the perfect conditions for frost quakes
Some studies suggest that frost quakes could become more common due to climate change, with increasing occurrences of warm, wet winter air masses leading to more frequent conditions suitable for frost quakes