Ice circle

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Ice disk on Vigala river (Estonia) filmed by a drone, January 2019.
Ice circles on the Doncaster River, Quebec
A long exposure image showing the rotation of the large ice circle on the Esopus Creek in New York

Ice discs, ice circles, ice pans, or ice crepes are a natural phenomenon that occur in slow moving water in cold climates. They are thin circular slabs of ice that rotate slowly on a body of water's surface.

Types[edit]

A collection of small ice pans (the largest about 30 cm [12 in] in diameter) was observed on the River Llugwy at Betws-y-coed, North Wales in December 2008. A fortnight of no rain had resulted in low water levels, and there had been sub-zero temperatures for a week.

Ice discs[edit]

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.[1] As the disc rotates, it grinds against surrounding ice — smoothing into a circle.[2] A relatively uncommon phenomenon, one of the earliest recordings is of a slowly revolving disc spotted on the Mianus River and reported in an 1895 edition of Scientific American.[3][4]

Ice pans[edit]

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 water’s edge". As water cools, ice crystals form into 'frazil ice' and can cluster together into a pan-shaped formation.[5] 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 and a low centre.[6]

Formation[edit]

Conditions[edit]

It is believed that ice circles form in eddy currents.[7] It has been shown that existing ice discs can maintain their rotation due to melting.[8]

Physics[edit]

Ice circles tend to rotate even when they form in water that is not moving. The ice circle lowers the temperature of the water around it, which causes the water to become denser than the slightly warmer water around it. The dense water then sinks and creates its own circular motion, causing the ice circle to rotate.[9]

Size[edit]

An unusual natural phenomenon, ice disks occur in slowly moving water in cold climates and can vary in size, with circles more than 15 metres (49 ft) in diameter observed.[10][11][12][13] Ice Circle of Vana-Vigala in Estonia is reported to have had a diameter of over 20 meters,[14] whilst one approximately 298 feet (91 meters) in diameter appeared in Westbrook, Maine in January 2019.[15]

Notable Examples[edit]

Ice discs have most frequently been observed in Scandinavia and North America. An ice disc was observed in Wales in December 2008 and another one in England in January 2009.[16][2][17] An ice disc was observed on the Sheyenne River in North Dakota in December 2013. An ice circle of approximately 15 m (50 ft) in diameter was observed and photographed in Lake Katrine, New York on the Esopus Creek around January 23, 2014. In Idaho, extreme weather led to a rare sighting of an ice disc on the Snake River on January 22, 2014.

On January 14, 2019, an ice disc approximately 298 feet (91 metres) wide on the Presumpscot River in Westbrook, Maine, United States drew wide media attention.[18][19][20] A smaller disc was reported by park rangers in Baxter State Park, in northern Maine, the same month.[21]

See also[edit]

References[edit]

  1. ^ Patrick Garrity (February 7, 2010). "VIDEO: Moscow Ice Disk a rarity of nature". Burlington FreePress.com. Archived from the original on July 30, 2012. Retrieved 19 February 2010.
  2. ^ a b David Derbyshire (13 January 2009). "Ice one! Walker discovers 10 ft-wide, spinning frozen circle in British waters for the first time". Mail Online. Daily Mail. Retrieved 2009-01-13.
  3. ^ Bates, J. M. (9 February 1895). "A revolving ice cake". Scientific American. 72 (6): 86. Retrieved 30 November 2013.
  4. ^ Rickard, B et al: Unexplained Phenomena, page 190. Rough Guides, 2000.
  5. ^ Joe Desloges. "Perfect "Ice Circle" Forms near Toronto, Canada". Retrieved 14 January 2009. cited in: Scroggins, Kate; Roberts, Rob (18 December 2008). "Man stumbles on round, spinning 'creek circle'". Posted Toronto. National Post.
  6. ^ Joe Desloges. "Perfect "Ice Circle" Forms near Toronto, Canada". Retrieved 14 January 2009.
  7. ^ "Crop Circles in the Ice: How Do Ice Circles Form?". Modern Notion. 2015-12-22. Retrieved 2019-01-16.
  8. ^ Dorbolo, S; Adami, N.; Dubois, C.; Caps, H.; Vandewalle, N.; Barbois-Texier, B. "Rotation of melting ice disks due to melt fluid flow". Phys. Rev. E. 93: 1–5. doi:10.1103/PhysRevE.93.03311 (inactive 2019-02-22).
  9. ^ MacFarlane, Drew. ""Maine River's Massive Disk of Spinning Ice a Sight to Behold"". The Weather Channel. Retrieved March 18, 2019.
  10. ^ Daniel Ostler. "Rare Sighting of an Ice Disk in Idaho". news.yahoo.com. Archived from the original on 2 February 2014.
  11. ^ "Giant ice circle spinning in Esopus Creek". recordonline.com. Retrieved 2019-01-16.
  12. ^ Blake Nicholson, Unusual ice circle forms in North Dakota river, November 26, 2013, Associated Press
  13. ^ Pete Thomas, Giant spinning ice circle discovered in North Dakota’s Sheyenne River, November 26, 2013, GrindTV
  14. ^ Jaan Viska: Jääratas pöörlemas Vana-Vigalas – mitte ainult kylauudis.ee, 11. jaanuar 2017
  15. ^ "Massive spinning ice disc forms in US river". BBC News. Retrieved 2019-01-16.
  16. ^ "Ice disc brings touch of Scandinavia to Devon river". Times Online. The Times. 14 January 2009. Retrieved 22 April 2010.
  17. ^ "Spinning ice disc phenomenon seen in British river for first time". Telegraph.co.uk. Telegraph Media Group Limited. 13 January 2009. Retrieved 22 April 2010.
  18. ^ "Ice disk mania draws crowds, boosts business in Westbrook". WMTW ABC News. 19 January 2019. Retrieved 19 January 2019.
  19. ^ "Massive spinning ice disc forms in US river". BBC News. Retrieved 2019-01-16.
  20. ^ "Onlookers share theories, find meaning in giant Maine ice disc". Bangor Daily News. Retrieved 2019-01-16.
  21. ^ "Westbrook isn't the only place in Maine with an ice disk". Millinocket, Maine: WMTW ABC News. Associated Press. 18 January 2019. Retrieved 19 January 2019. Officials at Baxter State Park in northern Maine shared a photo of an ice disk that's about 30 or 40 feet wide, located in wilderness more than 200 miles north of much larger disk that formed in Westbrook.

Further reading[edit]

External links[edit]