Wednesday, April 25, 2012
Ice Circles a rare Phenomenon
An ice circle is a rare phenomenon that occurs in slow moving water in cold climates. It consists of large discs of ice that rotate slowly in the water. It is believed that they form in eddy currents. Ice circles have most frequently been observed in Scandinavia and North America, but one was recorded in Britain in January 2009. Ice circles occur at bends in the 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 perfect circle.