Snow Donuts
Naturally occuring snow "doughnuts" spotted along Washington's North Cascades Highway, State Route 20.

They're sometimes called snow rollers. They form when there is a hard layer on the snow on a steep slope and it gets covered by several more inches of dense snow. Then all it takes is 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 may roll down the hill and collapse, creating what the WSDOT avalanche control crews call a pinwheel. Or it may 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. As soon as the sun comes out and it warms up, the doughnuts will be gone, faster than a visit from Homer Simpson.
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