Dozens of eerily perfect circles of slushy ice, known as "ice pancakes," have been floating on the surface of a Scottish river after temperatures in the U.K. unexpectedly plummeted.
Callum Sinclair, project manager for the Scottish Invasive Species Initiative (SISI), spotted the stunning circular sheets of ice Dec. 9 on the River Bladnoch in Wigtownshire, Scotland. Pictures of the peculiar pancakes taken by Sinclair were shared on the SISI Twitter (opens in new tab) page on Dec. 13, along with a short video (opens in new tab) of the icy discs bumping into one another and being washed downstream by fast-moving currents.
"I've seen ice pancakes occasionally before," Sinclair told Live Science in an email. "But these were particularly interesting" because of their perfect shape, he added.
Photos shared in the comments of the SISI post also revealed that ice pancakes have formed on the River Kelvin near Glasgow and the River Esk in the Lake District in northwest England in recent days.
Ice pancakes are relatively rare structures that tend to form in very cold oceans, lakes and rivers, according to the U.K. Met Office (opens in new tab).
On rivers, the pancakes form when frozen foam on the water's surface gets trapped in a spiraling current known as an eddy. As other bits of frozen foam and ice hit these forming discs, the debris joins onto the nascent pancakes, which causes them to grow, according to the Met Office.
On open water, the pancakes form when surface ice gets broken up and rounded out as currents and waves cause the icy chunks to bash into one another, according to the Met Office.
Ice pancakes can grow to between 8 and 79 inches (20 and 200 centimeters) across, and although they look like solid discs, they are often quite slushy and easily break apart when lifted up, according to the Met Office.
Although the icy discs dot the Great Lakes of North America and the oceans surrounding Antarctica, where temperatures often fall well below freezing, ice pancakes are much rarer in U.K. rivers.
However, an unusually cold snap, caused by an area of low pressure that got trapped by surrounding areas of high pressure over Russia and Greenland, has caused temperatures across the U.K. to fall below freezing for more than a week, according to the BBC (opens in new tab).
The lowest temperature recorded during the cold snap so far was 0.8 degrees Fahrenheit (-17.3 degrees Celsius) in Aberdeenshire, Scotland on Dec. 12, according to the BBC.