Sunday Science: Frost Quakes - WCAX.COM Local Vermont News, Weather and Sports-

Sunday Science: Frost Quakes

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SOUTH BURLINGTON, Vt. -

Once you chip away the snow that's packed in now, this crack right here looks like any other piece of pavement that has taken a beating from the elements. Except that it might be evidence of a frost quake. 

"It actually sounded like there was a truck or something that hit the back of our office and I went out back to see if ice had fallen or something like that, but nothing there," says Enterprise employee Phil Seidel. "I was checking a car back in a little later in the afternoon and I actually tripped over this crack here."

Reporter: "And so you guys definitely didn't notice this before then?"

Seidel: "No, absolutely not."

Frost quakes, or cryoseisms, happen when rain soaks the ground and then a flash freeze sweeps in to harden it. When water freezes into ice it expands and can break the ground.

"You can hear a booming sound and you can feel the shaking. But it's very localized. These are very localized events because they're shallow events," says Vermont State Geologist Larry Becker. "You don't feel them over a wide area."

Though Becker says frost quakes are actually pretty common, it is rare for them to cause damage like you see in the Enterprise parking lot.

"In general these are not very energetic events," he says. "You don't see the breaks in the ground, they're underneath the snow, usually it's a shallow layer of snow cover."

Becker says the freezing rain from December's ice storm, followed by a sharp cold -- and with little snow cover on the ground to act as insulation-- were perfect conditions to create the quakes.

We've had hundreds of people writing in the last few weeks saying they have heard these mysterious booms, some wondering if trees had fallen, others saying that Jack Frost just might be knocking on their doors.

Becker says it's hard to say for sure that what people are hearing and what happened in the Enterprise parking lot are frost quakes because seismic reports have yet to confirm any. But what people describe fits the bill.

"It's not every year that you hear a lot of reports about them but we have seen them before in Vermont," he says.

Becker says people shouldn't be concerned. The quakes aren't strong enough to do much more than localized breaking of soil or rock or maybe knock something off a shelf. And more often than not they're a phenomeon you might hear, but you're probably not going to find any evidence.

 

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