It’s been awfully cold in many parts of the US this week. As I tried to ignore the wicked wind outside, I thought, hmm, this is frost quake season. Sure enough, the Chicago area, hit hard by an Arctic air blast, reported frost quakes this week.
Frost quakes cause localized noise and shaking
Most people have never heard of frost quakes (sometimes called cryoseisms, although this normally refers to cracking of lake and sea ice). New scientific observations suggest that populations in regions prone to frigid winter temperatures will experience them more often. So, now is the time to get up to speed on this icy topic of spooky geology.
Frost quakes are one cause for mysterious booms and shaking heard by northern residents who are not used to earthquakes. They are not uncommon in the upper Midwest and New England, from January to March. Caused by the rapid expansion of water (thermal stress) as it freezes underground, the energy from the expansion releases suddenly, creating a cracking or booming sound, breaking rock layers, fracturing roads, and ripping tree roots.
Frost quakes are more likely to occur where the ground is saturated (after heavy rains or having a high groundwater table) and when rapid freezing occurs – when the temperatures drop to far below freezing over 8 hours.
Frost quakes are not deadly
Frost quake events are very localized and short-lived, however, if the explosive expansion happens near homes or structures, there is the chance that the shaking can cause moderate damage similar to small earthquakes. Frost quakes cannot create shaking and damage to the extent that a geologic quake can, but ground fractures and heaves can damage foundations, land surfaces, and roads. Frost tremors, which have more irregular waveforms, are less violent expressions of the stress release.
Lessons from Finland
Finland seems to be particularly susceptible to frost quakes. In January 2023, the Finnish town of Talvikangas experienced 26 frost quakes in 7 hrs, the greatest number recorded so far. A recent study from Finland will soon be published showing that wetlands, swamps, and irrigated areas, will more likely experience frost quakes.
- Frost quakes are a growing problem in Finland and other sub-Arctic countries
- Frost Quakes Shake Up Finland’s Wetlands
Frost quakes are typically associated with lack of snow cover. Snow provides some insulation against the rapid freezing that creates the stress leading to the sudden release. Climate change suggests that greater rainfall and less snow will be the trend in northern areas. The reduction in Arctic ice creates a destabilization of the Jetstream that allows frigid air masses to dip south, resulting in the cold zap like we got this month.
As the Finnish study showed, we would be wise to take frost quakes more seriously, as their occurrences may be increasing. Certain structures (utility lines, roads, water towers, power generating facilities, bridges, etc.) should be evaluated for risk from frost quakes even though they are outside typical fault-related seismic risk zones.
More: History of mystery booms