Why Does Snow Squeak When You Step On It?

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With Winter Storm Jonas expected to dump tons of snow on a large swath of the East Coast over the next few days, you might be trying to figure out if you have enough bread, milk, and eggs (and booze!) at home to get through the weekend. We’re also pondering another important question—why is snow, which is so quiet when it’s falling out of the sky, so loud on the ground, squeaking, creaking, and crunching under our boots? (If you’re not from a snowy part of the country, you can hear what we’re talking about in the video below).

Snow is made up of ice crystals. While ice is a solid, it actually has a thin (as in, a few nanometers) quasi-liquid layer (QLL) on its surface. Michael Faraday, better known for his work on magnetism and electrochemistry, first suggested this idea in the 1850s. While scientists have confirmed it since then, the origins and many of the characteristics of the QLL are unclear.

One thing we do know, though, is that the thickness of the QLL depends on temperature. When snow is warmer, the QLL around all those ice crystals is softer. When you step on the snow, the National Snow and Ice Data Center explains, you compress the crystals, but the liquid allows them to quietly slide past each other. When snow is colder and the QLL is stronger, there’s more friction between the crystals, and they don’t slide so easily. When you step on colder snow, the crystals rub against each other and also break, making that familiar squeaking sound.

Around 14 degrees Fahrenheit seems to the dividing line between squeaky and non-squeaky snow. Temperatures in the region getting hit by Jonas will be well above that through the weekend, so we’re probably in for a quiet storm.

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January 22, 2016 - 9:30am
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