Have You Heard a Frost Quake? | Boundary Waters Blog

Have You Heard a Frost Quake?

I have listened to the sound of booming ice on the river and the loud cracks and bangs as the house or deck freezes but I don’t think I’ve ever heard a frost quake. I’m not sure I’ve even heard the term “frost quake” before.  If you’re like me and have no clue what one is then read on.

Who, What, Why: What are frostquakes?

Loud explosions heard in parts of Canada are being blamed on a phenomenon called frostquakes, says Tom Geoghegan.

Ontario is no stranger to temperatures approaching -20C (-4F) but in recent days the winter freeze has been accompanied by unusual sound effects – bangs waking people up.

@sydney_grieve was one of many to tweet: “Heard a loud bang outside of my room at 2am. My whole family was searching the house thinking someone broke in. #frostquake”

Emergency services in the Greater Toronto Area received reports of loud noises, prowlers and thuds on the roof. Few of those calling in expected to be told it was probably the weather.

Known to experts as cryoseisms, frostquakes happen when moisture that has seeped into the ground freezes very quickly. It expands and builds up pressure, causing the frozen soil or rock near the surface to crack, emitting a sound that people have likened to a sonic boom.

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The answer

  • The loud cracking of frozen soil caused by expanding ice beneath the surface
  • It is uncommon and requires a plunge in temperatures following wet weather

They’re not very common because they require such a rapid change in temperature. In southern Ontario, a drop from 5C (41F) to about -20C (-4F) was preceded by an ice storm, which ensured there was a lot of moisture in the ground that became ice.

That doesn’t happen every year, says Geoff Coulson of Environment Canada, who says the term “frostquake” is new to him. It’s like a very weak earthquake and the house might shake but there is hardly ever significant damage, he says, and it will only be felt or heard within a kilometre (0.6 miles) at most.

One peculiarity is that it rarely sounds like it is coming from below, due to the way the soundwave travels – one couple thought a truck had hit their house, while others feared a tree had fallen on the roof.

“The peak time is between 3am and 8am, and that’s related the depth of cold at that time,” he says. But sometimes the ice slowly builds and the explosion may happen days after the temperature drops.

Frostquakes have been reported before – northern US states such as Ohio had a similar experience in 2011. But the phenomenon was not widely reported until this winter, says Coulson, largely due to social media.

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