الاثنين، 29 أبريل 2013

"Ice needles" emerge from a Minnesota lake


Filmed at Medicine Lake in Minnesota by Nadalie, via KARE 11 News.

This is occurring during the (delayed this year) spring ice-out phase, so the ice moving ashore is different from the ice heaves that occur in midwinter when a solidly frozen ice surface expands on a warmer-than-usual winter day.  Here the ice is being driven ashore presumably by prevailing winds.

The wondrous aspect of this particular event is the needle-like shape of the ice crystals.  One type of needle-shaped ice is frazil ice, but I think that's different - at least in the video I bloggged some years ago of frazil ice moving at Yosemite - because frazil ice forms in supercooled water.  I think what is seen here is the result of fracturing of the ice sheet.

But the video is cool.  Wish I had been there to see it happen.

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