A mysterious circular ice that spins around in the river

I introduced earlier the

mysterious natural phenomenon 'Snow Roller' in which donut-shaped snow rolls like after a large number of children have played without anyone, but this time it is also a mysterious natural phenomenon.

This is because when it gets cold enough to snow, there is somehow circular ice on the edge of the river, and because it is far from the shore, it spins around. It doesn't seem to have a specific name, but it seems to be a rare phenomenon.

Details are as below.
First of all, it is easy to understand by watching the video.
VIDEO: Moscow Ice Disk a rarity of nature | The Burlington Free Press | Burlington, Vermont

It's slowly spinning like this. It's like a rotating floor in a merry-go-round, and I suspect it's mechanical, but it's a natural phenomenon. This was taken near Moscow.

A beautiful circle.

This was found on Newfoundland, Canada.

You can see that the river is formed outside the curved part.

Also, if there is no snow, it seems that you can see a transparent figure because it is only ice.

It is believed that this phenomenon is caused by ice forming on the vortex of the river surface when the flow of the river is slow, and eventually forming a beautiful circle. It seems that some things in the 200m diameter class have been observed in Sweden, but it seems difficult to see them in the neighborhood because it can not be done unless some conditions are met.

Spinning ice disc phenomenon seen in British river for first time --Telegraph

The Telegram --St. John's, NL: Local News | A perfect circle

in Note,   Video, Posted by logc_nt