Cryoseism

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A cryoseism, also known as a frost quake^[1]^[2] or ice quake, is a non-tectonic seismic event caused by a sudden freezing action in soil or rock materials saturated with water or ice.^[3] As water seeps down into the rock, it freezes and expands, putting stress on surrounding rock. This builds up until it is relieved explosively in a cryoseism.^[4]

Cryoseisms can also be caused by sudden glacial movements, due to the formation of a thin veneer of liquid water under a glacier from surface melting. Usually, a glacier would stick to the rough bedrock, but the hydraulic pressure acts as a lubricant, allowing it to slide several metres at once.^[5]^[6] This type of cryoseism can last thousands of seconds long.^[7]

As the requirements for cryoseisms to occur are not yet defined, their prediction is still not possible. Cryoseisms constitute a significant factor in structural design and engineering.^[3] Links have been made between global warming and the frequency of cryoseisms.^[7]

1 Effects
2 Occurrences
- 2.1 Location
- 2.2 Precursors
3 See also
4 References

[edit] Effects

Cryoseisms are often mistaken for minor or intraplate earthquakes.^[3]^[8] Although the outward signs of a cryoseism often appear similar to those of an earthquake, with tremors, vibrations, ground cracking and related noises^[2] such as thundering or booming sounds,^[4] cryoseisms can be distinguished from earthquakes through meteorological and geological conditions.^[3] Cryoseisms can have an intensity of up to VI on the Modified Mercalli Scale.^[3] Furthermore, cryoseisms often exhibit high intensity in a very localized area,^[2] in the immediate proximity of the epicenter,^[8] as compared to the widespread effects of an earthquake.^[3] The vibrations of a cryoseism are lower frequency than normal earthquakes as well.^[5] As a result, some seismic monitoring stations may not record a cryoseism.^[8] Although cryoseisms release drastically less energy than tectonic events, and their seismic waves have stronger attenuation,^[9] it should be noted that cryoseisms can still cause damage or significant effects at the site.^[2]

Some reports have indicated the presence of "distant flashing lights" before or during a cryoseism, possibly due to the electrical changes when the rocks are compressed.^[4] Cracks and fissures can also appear, as the ground may contract and split apart from the cold.^[2]^[8] These cracks can range from several centimetres to several kilometres long, and are usually superficial, with a single linear fracture or multiple ones as well as small vertical and moderate lateral displacement.^[3]

An ice quake prevented Walter Wellman and his team from venturing to the north pole in 1898.^[10]

[edit] Occurrences

[edit] Location

US States with reported cryoseisms.

Geocryological processes have been reported to cause tremors as early as 1818.^[3] In the United States, such events have been reported in the states of Connecticut,^[2] Maine,^[2] Massachusetts,^[2] Michigan,^[11] upstate New York,^[2] Vermont^[2]^[8] and Wisconsin,^[1] all in the Northern and Northeastern United States.^[4] Cryoseisms have also surfaced in Ontario, Canada.^[12] Also, some glacier related phenomena have been reported in Greenland,^[13] Alaska,^[14] the Antarctic Prince Charles Mountains^[15]and Ross Island,^[9] and Iceland (Grímsvötn).^[16]

[edit] Precursors

Cryoseisms typically occur when temperatures decrease from above freezing to subzero rapidly, in the first cold snap of spring.^[2]^[8] They usually occur from midnight to dawn, during the coldest part of the night.^[3] However, glacier related cryoseisms could occur in the warmer months of summer, due to the permanent nature of glacial ice.^[5] Typically, cryoseisms occur 3 to 4 hours after significant changes in temperature.^[17] Due to the perennial or seasonal frost conditions involved with cryoseisms, these events are limited to temperate climates which experience seasonal variation with subzero winters. Furthermore, the ground must be saturated with water, which can be caused by snowmelt, rain, sleet or flooding.^[3] Usually, the site of a cryoseism has little or no snow cover to insulate the ground.^[2]^[3] Geologically, an area would be most susceptible to cryoseisms if the ground is made of permeable materials like sand or gravel, which are affected by frost action.^[3] Usually, after large cryoseisms, there is no reported seismic activity for several hours, an indication that accumulated stress has been relieved.^[17]