Formation of ice circle in rivers is a rare and amazing natural phenomenon in which a circle made of ice rotates slowly in water. Ice circles appear in slow moving water and are generally found in places where the weather is very cold. They are generally 15 to 20 feet in diameter. Ice circles are normally found in the cold rivers of Scandinavia or North America but occasionally they have been observed in other parts of the world. People have observed ice circles in rivers of Wales and England in 2008 and 2009 respectively.
Ice Circles in Rivers Explained
Ice circles are believed to form in eddy currents. Eddy current is the reverse current which is created when the fluid encounters an obstacle. Ice circles occur at bends in the river. The accelerating water creates a force known as ‘rotational shear’. This force breaks off a chunk of ice and twists it around. As the disc rotates, it grinds against surrounding ice – smoothing into a perfect circle. Watch this video of an amazing ice circle.
Note : The video above is not the property of learnodo-newtonic.com. It is embedded from the youtube channel of Jérôme Joncas. It may not work in the future.
Ice Circles Visible from Space
The above explanation for the formation of ice circles should not be confused with the two massive ice circles visible from space, which were spotted in Russia’s Lake Baikal by astronauts aboard the International Space Station, in April 2009. The diameter of these circles was in kilometers and they cannot be observed even from mountains.
This incident had led to rumors that these ice circles had been created by an alien machine. The real reason behind their creation was the methane gas which was being released from the floor of the lake. Methane emissions can create a rising mass of warm water that moves in a circular motion due to Coriolis force, the phenomenon caused by the Earth’s rotation that also helps in the formation of cyclones. When this circulating warm water comes in contact with surface ice it melts it in a ring shape thus forming a giant circle. Thus the ice circles which were visible from space were formed due to methane and not because of an alien machine!