This footage shows a naturally formed ‘ice disc’ floating on the surface of a partially frozen river and spinning on its own like a piece of clockwork.
The extremely rare natural phenomenon – which made headlines across the globe when it was spotted in Maine, US, earlier this year – was filmed by meteorologists in the city of Genhe, which is in North China’s Inner Mongolia Autonomous Region, on 3rd November.
The ice disc – also known as an ice pan or an ice crepe – was seen on the Genhe River, after which the city is named.
Video of the circular disc measuring a reported 2 metres (6 feet) in diameter shows it appearing to spin on its own in an anticlockwise direction.
The unusual sight has drawn local residents to the banks of the Genhe River, which has a reported average temperature of minus 5.3 degrees Celsius, and which freezes over more than 200 days per year.
It is still not entirely how exactly these rotating slabs of ice are formed, but it is believed that the existence of whirlpools know as eddy currents help turn the discs in place.
However, 2016 research done into the physics of ice circles by the University of Liege in Belgium concluded that similar natural discs tend also to rotate themselves in dead water.
In the absence of currents or moving water, the melting ice disc lowers temperatures around it, causing the cooler, denser water to sink, thus creating a circular motion.
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