They are not UFOs or crop circles in ice. They are a natural phenomena.
Amazing Ice Circle Appears On River Live Science - November 26, 2013
A spinning ice disk spotted on the Sheyenne River in North Dakota is a totally natural phenomenon and not the work of aliens or secret government spies, according to reports. Retired engineer George Loegering saw the giant frozen circle on Saturday (Nov. 23) while on a hunting trip with relatives, the Associated Press reported. About 55 feet (17 meters) around, the icy disk was spinning in the river current like a record on a turntable. The massive pancake-shaped ice pans often turn up on flowing rivers in cold climates. Video and photos posted online show similar disks discovered in Canada, England and Sweden during winter.
An ice disc, ice circle, or ice pan is a natural phenomenon that occurs in slow moving water in cold climates. Ice circles are thin and circular slabs of ice that rotate slowly in the water. It is believed that they form in eddy currents. Ice discs have most frequently been observed in Scandinavia and North America, but they are occasionally recorded as far south as England and Wales. An ice disc was observed in Wales in December 2008 and another was reported in England in January 2009. Ice circles vary in size but have been reported to be more than 4 metres (13 ft) in diameter.
Ice discs form on the outer bends in a river where the accelerating water creates a force called 'rotational shear', which breaks off a chunk of ice and twists it around. As the disc rotates, it grinds against surrounding ice - smoothing into a circle. A relatively uncommon phenomenon, one of the earliest recordings is of a slowly revolving disc was spotted on the Mianus River and reported in a 1895 edition of Scientific American.
River specialist and geography professor Joe Desloges states that ice pans are "surface slabs of ice that form in the center of a lake or creek, instead of along the waterÕs edge. As water cools, it releases heat that turns into frazil ice" that can cluster together into a pan-shaped formation. If an ice pan accumulates enough frazil ice and the current remains slow, the pan may transform into a 'hanging dam', a heavy block of ice with high ridges low centre.
Ice Circle in Michigan - December 2006
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