North Dakota retired engineer George Loegering has found a rare spinning disk of ice in the Sheyenne River, a weather phenomenon experts say likely was caused by cold, dense air, and an eddy in the river.

There it was, just sitting in the Sheyenne River — a perfect circle of ice, about 50 feet in diameter, gently rotating in the water.

George Loegering's discovery of the huge ice disk last Saturday has been a big hit over the Web after his video of the phenomenon went viral.

"It's an amazing wonder," Loegering, 73, of Casselton, N.D., said in the video, which was reproduced by the Associated Press. "I don't have a clue how it did it, but that thing is rotating, as you can see."

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A National Weather Service hydrologist and a weather service meteorologist told the Associated Press that the ice circle could be attributed to the cold, dense air that collected over North Dakota last week — nothing nefarious.

The river began to freeze from the cold, they said, but slowly enough that tiny chunks of ice probably got caught together in an eddy and formed a tidy little galaxy spinning out on the water.

"It's not a continuous sheet of ice," Allen Schlag, a National Weather Service hydrologist, told the AP. "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."

In other words, don't try to walk on it.

Similar phenomena have been documented in colder states and countries. You can see videos of somewhat similar disks here, here and here.

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