Perfect Snow Donuts

Mike Stanford, an avalanche-control expert with the state Department of Transportation (WSDOT), found a pleasant surprise while he was doing some avalanche-control work.

Stanford found frozen doughnuts of snow on the top of Washington Pass in the North Cascades. These perfectly shaped doughnuts had rolled down the mountainside and frozen in place!

Some of the larger snow rollers, as they are commonly called, was about 24 inches tall, he said. They were even large enough for him to put his head through the hole.

Stanford commented that snow rollers form when there is a hard layer on the snow, covered by several more inches of dense snow. "Then you add a steep slope and a trigger such as a clump of snow falling out of a tree or off of a rock face."

As gravity pulls a clump down, it usually rolls down the hill and collapses, creating what the WSDOT calls a pinwheel. Or it will not roll at all, and come down in an avalanche of snow. But if the snow is the perfect density and temperature, it rolls down leaving a hole in the center, Stanford said.

via Spluch