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A cryoseism is a seismic event that can be caused by a sudden disruptive action produced in the frozen ground or in the rock saturated with water or ice. When water infiltrated into the ground freezes, the increase in volume puts stress on the surrounding rock.
The tension builds up until it is released sometimes explosively, resulting in a so-called cryoseism. The ice at the base of the glacier can remain anchored to the rock for a long time, but the hydraulic pressure acts as a lubricant, causing it to suddenly slide many meters.
This type of cryoseism can be short-lived or remain active for a few minutes. The genesis of cryoseisms is not yet fully understood; their prediction is not yet possible and is an important factor in structural design and engineering.
Typically cryoseisms occur when temperatures decrease rapidly until they drop below zero in the first period of intense cold in spring. They usually occur between midnight and dawn, during the coldest hours of the night. However, glacier-related cryoseisms can also occur in the warmest months of summer, due to the permanent nature of ice in glaciers.
In general, cryoseisms occur in the three to four hours following significant changes in temperature.
Cryoseisms and their dangers
The perennial or seasonal frost conditions linked to cryoseisms limit these events to temperate climates where seasonal variations give rise to winters with temperatures below 0 °C.
The area of a cryoseism is generally covered with little or no snow which would have the effect of thermally insulating the soil. Geologically, areas made up of permeable materials such as sand or gravel, which are susceptible to the action of frost, are the most likely candidates for freezing.
After large cryoseisms, there is generally no seismic activity for several hours, indicating that the accumulated voltage has been discharged. Freezing earthquakes are often confused with minor earthquakes or interplate earthquakes.
Although the outward signs often appear similar to an earthquake, with tremors, vibrations, cracking of the ground, and related crashes such as the sound of thunder or bombs, cryoseisms can be distinguished from earthquakes by meteorological and geological conditions.
