What Are Icequakes and Where Do They Happen?
Icequakes happen when water in the ground freezes very quickly and expands. As groundwater becomes ice, it breaks up the soil and rocks around it. In some cases, it can even cause cracks in the ground above. A major event may cause a fracture visible on the ground, ground shaking, tremors, vibrations, or explosive noises easily confused with an earthquake. This type of ground shaking event is not an earthquake. Earthquakes occur much deeper in the ground and are not associated with cold periods.
Icequakes are also called frost quakes or cryoseisms, a seismic event that may be caused by a sudden cracking action in frozen soil or rock saturated with water or ice. As water drains into the ground, it may eventually freeze and expand under colder temperatures, putting stress on its surroundings. This stress builds up until relieved explosively in the form of a cryoseism.
Another type of cryoseism is a non-tectonic seismic event caused by sudden glacial movements. This movement has been attributed to a veneer of water which may pool underneath a glacier sourced from surface ice melt. Hydraulic pressure of the liquid can act as a lubricant, allowing the glacier to suddenly shift position. This type of cryoseism can be very brief, or may last for several minutes.
The requirements for a cryoseism to occur are numerous; therefore, accurate predictions are not entirely possible and may constitute a factor in structural design and engineering when constructing in an area historically known for such events. Speculation has been made between global warming and the frequency of cryoseisms.
They’re common across Antarctica. Experts there say Earth’s coldest continent has had hundreds of thousands of them in recent years. They’ve also shared that most icequakes happen at night when temperatures drop. Rising temperatures cause Antarctic ice to melt. This makes water that can freeze again to cause an icequake.
When ice in Antarctica melts, it often makes an icy slush. At night, as temperatures drop, the top layer of this slush freezes quickly. As the liquid below the surface starts to freeze, it expands. This causes the top layer to warp and crack. This causes an icequake, much weaker than earthquakes but it makes a loud pop or boom.
They also occur in Greenland, most often near glaciers. You might also hear an icequake in Canada, as well as in the midwestern and northeastern United States. On January 1, 2018, Alberta experienced icequakes near Gull Lake, Pigeon Lake, Wabamun Lake, and Lac Ste. Anne. These icequakes were local magnitude (ML) near 2.0 and residents felt the ground movement. Residents said they heard loud boom (or popping) sounds and felt ground shaking that rattled houses – loud and intense enough to wake them from sleep.