Orbiting ice disc
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A circling disk of ice is a rare natural phenomenon in winter . It arises, for example, on bulges in flowing waters when an ice sheet forms on a slowly rotating vortex , which takes on a circular shape due to the friction with the ice on the bank. Ice disks with diameters of several meters up to 200 meters are known. Ice disks were mainly observed in countries with a cold temperate climate such as the north of the USA , Canada , Scandinavia , the Arctic and, less often, in Great Britain .
The phenomenon of circling ice disks occurs when rivers thaw, mainly in spring. The disks rotate around themselves even when the water is still. Even if no current can be seen, they rotate at a constant speed. An ice disc with a diameter of around 20 meters that has appeared regularly since 2004 is the Vana-Vigala ice wheel on the Vigala River in Estonia . There are reports and documents on the sighting of an ice disc in 2013 on the Sheyenne River in the US state of North Dakota with a diameter of about 15 meters and the observation of a disc in Vestaburg in the US state of Michigan in 2017. In January 2019, on the Presumpscot River in Westbrook (Maine) observed an ice sheet about 100 meters in size.
A circling ice disc was described in the US magazine Scientific American as early as 1895 after a sighting on the Mianus River near Bedford in Westchester County in the US state of New York .
Physicists at the University of Liège carried out laboratory tests in 2016 which showed that melting ice discs in relatively warm water can start rotating even if there is no external current drive. The phenomenon occurs when the melt water under the pane has cooled to 4 ° C and begins to sink in the warmer water surrounding it. The sinking of the meltwater leads to turbulence under the ice layer, which causes the disk to rotate.
See also
Web links
- Daniel Lingenhöhl: Mystery of circling ice discs solved. Spektrum.de , April 22, 2016
- Photo and video of a circling oak slice on the River Dee
- Video of a rotating ice circle ( Mississauga , 2008) on Youtube (00:40 minute)
- Mysterious: rotating ice floe discovered ( Sheyenne River , 2013) on Youtube (01:00 minute)
- The rotating ice disc poses a puzzle. 20 minutes , November 28, 2013
- Rotating ice disc in Westbrook, Maine (drone footage; both videos from January 15, 2019):
Individual evidence
- ↑ USA: Rotating ice disc discovered on river. In: Kronenzeitung , November 28, 2013
- ↑ A rare winter phenomenon on video: The rotating ice disc. In: Aargauer Zeitung , January 11, 2017
- ↑ Lars Fischer: Winter phenomenon: gigantic ice circle rotates in the US river. In: Spektrum.de . January 16, 2019, accessed January 31, 2019 .
- ↑ JM Bates: A Revolving Ice Cake . In: Scientific American . Vol. 72, No. 6 , February 9, 1895, p. 85 (English, online view [accessed on February 2, 2019]).
- ↑ S. Dorboló, N. Adami, C. Dubois, H. caps, N. Vandewalle, B. Darbois-Texier: Rotation of melting ice disks due to melt fluid flow . In: Physical Review E . Vol. 93, Iss. 3, March 2016, doi : 10.1103 / PhysRevE.93.033112 (English, limited online view [accessed on February 2, 2019]).