Looking a bit like a cluster of frozen cowpats, peculiar “ice pancakes” appeared on the River Bladnock, Scotland, after a sudden drop in temperatures across the UK this month.
Project manager for the Scottish Invasive Species Initiative (SISI) Callum Sinclair snapped the images of these strange disks on December 9, sharing them to Twitter along with a video of them floating across the icy river.
The UK’s recent cold snap saw most of the country experiencing below-freezing conditions, with December 12 being the coldest day in the UK since 2010. The lowest temperature was -17.3 degrees Celsius (0.8 Fahrenheit) in Braemar, Scotland.
The sudden drop in temperature is thought to have caused the unusual phenomenon, and reports of similar sightings on a river near Glasgow and in the Lake District, Northwest England, suggest the formations could be occurring in other parts of the UK.
With each disk growing to between 20 and 200 centimeters (8-79 inches), this strange phenomenon is rarely found in the UK. Ice pancakes usually form in the Baltic Sea and around Antarctica, but they can sometimes be found floating on the Great Lakes in the US and Canada.
The disks can form as a result of two very distinct sets of conditions. They can either be created by waves forming pieces of ice that knock against each other in choppy waters, forming round edges and slowly growing. The rims around the edge of the ice pancake are formed when lapping waters join the rim of the already frozen disk and freeze to form an additional ring layer.
In the calmer conditions of a river, however, they’re formed when foam on the river surface begins to freeze. The frozen masses begin to join together and get sucked into a swirling current, called an eddy, causing them to form these circular shapes. They continue to grow as smaller bits of ice hit the disks and freeze to the outer rim.
Despite looking like solid, frozen disks, ice pancakes are often surprisingly slushy and brittle. In the correct conditions, the disks will begin to consolidate forming sheet ice, and when the water is choppy this sheet ice can bend to create ice ridges.