What Is an Ice Quake? Alaska Hit With Cryoseism Amid Northwest Heat Wave

Two ice quakes have been recorded in Alaska amid the record heat wave engulfing the Pacific Northwest.

United States Geological Survey (USGS) data shows that the two quakes occurred separately on Monday evening and Wednesday evening. Both hit near to the city of Juneau, which borders Canada.

Monday's quake hit at a magnitude of 2.7 and struck at a depth of 6.6 kilometers (a little over 4 miles). Wednesday's quake hit at a magnitude of 2.6 at a depth of 9.4 kilometers (around 5.8 miles).

At that strength, neither quake was likely to have been strongly felt, if at all.

An ice quake is a geological event in which ice expands during sudden warm periods and is unable to accommodate the change in volume, according to the Alberta Geological Survey (AGS).

This causes cracks and ridges to form in the ice, which can produce seismic waves that may then be recorded by seismographs. Ice quakes are not the same as earthquakes, which are instead caused by the shifting movements of tectonic plates.

Ice quakes may also be referred to as frost quakes, though the AGS makes a distinction between the two. It states that a frost quake occurs when very wet soil freezes quickly and expands, which then puts stress on the soil and causes it to fracture.

The Encyclopedia Brittanica, however, uses that same definition for both ice quakes and frost quakes.

Both are examples of a cryoseism—in which snow, ice, or rock suddenly cracks because of changes in stress, whether it be expansion or contraction.

Further complicating matters is the fact that scientists have known for years that melting glaciers have caused earthquakes in areas that are otherwise stable.

In a March 2021 research article, scientists found that ice loss near Alaska's Glacier Bay National Park has influenced the timing and location of earthquakes in the area.

In a summary of the paper, the University of Alaska Fairbanks, with which the study's lead author is affiliated, said the weight of glaciers can cause the land beneath them to sink. Likewise, this land can rise again when the glaciers melt.

Chris Rollins, the lead author, found a subtle correlation between this earth rebound effect and earthquakes.

Whatever the cause of the Alaska ice quakes, the fact remains that northwestern parts of North America are experiencing unusually hot temperatures at the moment.

In the Canadian province of British Columbia, in a village called Lytton, the country's all-time hottest temperature record was broken three times, with the highest recorded on Tuesday at 121.28F.

Crack in ice
A photo shows parts of a glacier in the Kenai Mountains near Primrose, Alaska, in September 2019. Ice quakes and frost quakes occur due to quick changes in stress. Joe Raedle/Getty