When I first saw this giant rotating ice disk spotted in North Dakota this week, I assumed it had to be some kind of human-created object, perhaps a new piece by famed land artist Andy Goldsworthy. The video above was shot by retired engineer George Loegering while hiking along the Sheyenne River. He estimates the rotating disk was some 55 feet in diameter and must have been forming for some time. The St. Paul Pioneer Press spoke with National Weather Service hydrologist Allen Schlag:
The cold, dense air—the air pressure Saturday in nearby Fargo was a record high for the city for the month of November, according to Gust—turned the river water into ice, but since the water was relatively warm it didn’t happen all at once. Floating bits of ice got caught in the eddy and started to spin in a circle.
“It’s not a continuous sheet of ice,” Schlag said. “If you were to throw a grapefruit-size rock on it, it would go through. It’s not a solid piece of ice—it’s a collection of ice cubes.”
Although extremely rare, ice disks do indeed appear naturally from time to time when conditions are perfect. Above are a few examples of people who have been lucky enough to stumble onto one while holding a camera. Learn more over on St. Paul Pioneer Press. (thnx Ben + all)