Summit County Citizens Voice

A close-up view of frazil ice on Dillon Reservoir.

Unusual ice crystals form in super-cooled, turbulent water

By Bob Berwyn

SUMMIT COUNTY — Even as the ice blanket on Dillon Reservoir starts to thin and break up, new, needle-like ice crystals have been forming close to shore, as super-cooled water is churned by the wind. It’s called frazil ice, and it’s an unusual formation that is found more frequently in alpine streams or in cold polar seas, where it’s the first stage of sea-ice formation.

Dynamic frazil ice floes have been well documented Yosemite National Park, where the Slushee-like mass forms temporary dams that cause streams to leave their channel until the blockages give way in a mini-flood. Check out this YouTube video of Yosemite frazil ice.

Frazil ice forms when the surface of the water cools quickly, like during the past few nights when cold winds blew across Dillon Reservoir. The resulting turbulence mixes the super-cooled water throughout its entire depth, encouraging the formation of tiny crystals. The turbulence prevents the ice from forming a sheet, but through a process called secondary nucleation, the frazil ice crystals multiply, sometimes reaching concentrations of 1 million crystals per cubic meter.

In the past few days, this slushy mass has been washing up on the shore of Dillon Reservoir. From a distance, it looks like snow, but you can check out the unusual ice formation up close in the vicinity of Heaton Bay.

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Filed under: daily photoblog, photography, seasons, Summit County Colorado Tagged: | Dillon Reservoir, nature photography, photo journalism, photography, Summit County Colorado, Summit County News, Summit County photos