Frostquakes may become more frequent due to climate change, researchers believe. © Christoph Hardt/imago/Symbolbild
The little-studied phenomenon of frostquakes is known from the USA, Canada and Finland. Climate change could make these tremors even more pronounced.
Oulu (Finland) – Sudden cracks in frozen ground can cause tremors to the earth's surface, such as the recent cold spell in the United States in February. These so-called frostquakes are usually harmless, but are often accompanied by seemingly menacing rumble of thunder. In some cases, the still relatively unexplored quakes can also cause damage to houses or infrastructure at extremely low temperatures. Due to advancing climate change, this weather phenomenon could become more frequent, researchers believe.
Frostquakes known from Canada, USA and Finland – accompanied by thunder, crashing or banging
Residents of Chicago reported loud bangs related to the shaking of the frozen ground in February during the extreme cold spell in the United States. Reports of this phenomenon have so far come from the USA, Finland and Canada, although the noise is sometimes described as a loud crash or rumble of thunder. Occasionally, the releasing tensions in the ground also resemble gunshots, as a video shows:
Damage to buildings possible: In Finnish city, cracks in the ground are sometimes 25 centimetres wide due to frost quakes
Unlike earthquakes, the vibration of frostquakes does not come from the depths, but is caused by bursting ice on the surface. The phenomenon was particularly evident in 2016 in the Finnish city of Oulu, which is located about 600 kilometers north of the capital Helsinki and thus in the subarctic zone.
In Talvikangas, a suburb of Oulu, 26 frostquakes occurred within a few hours, accompanied by loud crashes and causing several cracks in the ground as well as a 25-centimeter-wide gap. This is the result of a study by the Geological Survey of Finland, which was reported by the online science portal Spektrum. Damage to infrastructure and buildings is possible in such cases.
This is how frostquakes occur: a lot of moisture in the soil, followed by extreme cold snap
These weather phenomena, also known as ice quakes, occur when soils have absorbed a lot of moisture and there is a drastic drop in temperature afterwards. Then the water freezes and expands, which can subsequently lead to the described stresses, vibrations and sometimes cracks in the ground. Anyone who has ever put a warm beer bottle in the freezer and forgotten it there is quite familiar with the phenomenon of expanding water and the power it develops.
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However, there is a second theory about the origin of the ice quakes: the temperature differences in the different soil layers themselves could cause the stresses and not the expanding water. Frost earthquakes are comparatively unexplored, partly because the tremors often occur in sparsely populated areas such as the Arctic.
More frostquakes due to climate change, as global warming has a greater impact on the Arctic
Compared to tectonic earthquakes, frost earthquakes are less predictable and observable. However, researchers found a connection between the air temperature and the formation of the ice quakes. A team of researchers led by Jarkko Okkonen investigated the phenomenon in more detail and succeeded for the first time in recording the seismic activity of frostquakes. "In our study, we present a method to investigate the relationship between thermal stress and frostquakes," the scientists say.
To the publication
The data from the study "Connection between thermal stress and frost quakes" by the authors Jarkko Okkonen, Nikita Afonin, Emma Riikka Kokko, Elena Kozlovskaya, Kari Moisio and Roseanna Neupauer of the Geological Survey of Finland, the University of Oulu and the University of Coloarado Boulder were presented at the General Assembly of the European Geosciences Union in April 2023.
Link to the study
"We show that a rapid drop in temperature can cause a thermal stress that is higher than the fracture toughness and strength of the soil-ice mixture," the research team said. The incident in the city of Oulu was due to a rapid drop in air temperature from minus twelve to minus 29 degrees, it said. The conditions for ice quakes are especially favorable when a drastic cold snap is preceded by a mild and humid weather period, and the ground is covered by a layer of snow that is not too thick. Climate change favors extreme weather events and, according to experts, could make the sequence of mild weather and subsequent extreme frost more frequent.
According to the study, climate change could increase the number and intensity of frostquakes, as global warming is having a greater impact on the Arctic and warming it faster than other places in the world. However, there is still a lot of work ahead of the researchers: "The observations of recent decades and the analysis of the effects of climate change predict significant changes in snowpack and snowmelt, but the consequences for frozen ground and related phenomena such as frostquakes are unclear," the study says. However, the consequences of climate change are also becoming increasingly clear in other areas. Researchers at the University of Colorado, for example, found that more than half of all lakes worldwide lose water.