A rare and mysterious ice circle was discovered by retired engineer George Loegering, who spotted the ‘cool’ phenomena floating in the Sheyenne River in North Dakota this past weekend while vacationing with family. He estimates that the ice ring – rotating in the river “like a record turntable” – measured about 10 feet in diameter.
“I’m not sure how long it was there (spinning),” he told the Associated Press. “It had to be quite a long time. If you look at the picture, you can see growth rings on the disk,’ Loegering said. “That thing is rotating, as you can see.” He even described how concentric rings of ice near the ice circles’ edge made him think the ice circle was growing.
While a few similar disks have been reported – including in Canada, England and Sweden – scientists remain puzzled by the phenomena. As reported by the Associated Press, theories include:
Cold, dense air slowly froze the surface in bits and pieces, then got trapped in a river eddy.
“Frazil” ice — loose, needle-shaped particles of ice that can cluster together – forms as water cools and accumulates.
Ice circles form at bends in the river where the rushing water creates a force called “rotational shear.” This force can break off a piece of ice that rotates. As it spins, its edges become smooth as they grind against surrounding ice.
via Fjord of the Rings | Cosmic Soup.