Dear Tom,
Why is snow slippery?
Victoria Giesso, Chicago
Dear Victoria,
A thin layer of snow is slippery because, broadly speaking, it acts as a lubricant between our feet and the ground underneath. Deep snow, of course, is not slippery because it offers plenty of traction.
Ice, however, is genuinely slippery, and that is the more relevant issue. Based on new research at the University of California and elsewhere, we now understand that the surface of ice, regardless of the temperature that prevails outside, is covered with a layer of molecules that vibrate very rapidly, and they effectively give the ice surface liquid properties. That makes ice slippery.
It’s similar to the phenomenon that makes water-covered ice extremely slippery.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
