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What's a frost quake? The phenomenon could be the source of recent booms in York County

Written by Abbey Zelko/The York Daily Record | Jan 4, 2018 5:56 PM
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(York) -- Have you heard a mysterious boom this winter and couldn't figure out what caused it?

Don't worry. You're not alone.

Several people in York County have reported hearing booms since early December, said geologist Jeri Jones of Jones Geological Services.

Jones, who has been studying geology for 38 years, believes the sounds are caused by cryoseisms or "frost quakes," a phenomenon that occurs when the soil freezes and expands.

"Sometimes, you can actually see a crack running through your yard in the soil when it happens," he said.

Jones has been receiving reports of frost quakes from all over York County for the past four or five years, he said.

"It always happens about when we get our coldest spell - the first coldest spell of the year," he said.

The most recent one he is aware of occurred Tuesday in Monaghan Township. Three neighbors reported hearing a boom around 5:25 p.m. However, another York Countian reported hearing a boom as recently as Thursday morning, according to a post on Facebook.

Frost quakes are too small to be picked up by a seismograph, so they're difficult to prove, Jones said. They're not very loud, usually don't cause much shaking and can only be heard about 300 feet away. Jones compared the volume to the sound of a truck driving past the house.

But because the only people who reported hearing the boom in Monaghan Township were three neighbors who live close to each other, Jones feels confident that boom was most likely a frost quake.

"Based on the weather that's been going on up here, the timing for those is pretty good," he said.

Jones said he doesn't expect to hear many more reports of frost quakes this winter because, after more than a week of below-freezing temperatures, the ground is already frozen in most areas of the county. Frost quakes only happen the first time the ground freezes, he said.

But if someone does hear one, he encourages them to report it by emailing him at jonesgeo@comcast.net.

This story comes to us through a partnership between WITF and The York Daily Record

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