03 March 2011
Posted in 2008:
The two photos above are part of a set posted in the often-interesting English Russia website. They depict a large round slab of ice floating on water, surrounded by a flotilla of smaller ones. No explanation is offered for their creation.
It appears to me that these formations are occurring in a river (lower picture above and some of the others seem to show flowing water adjacent to the ice floes). If so, I suspect these form when floating ice reaches an eddy in the river, and the rotation of the water grinds the edges of the floes until they become circular.
Futility Closet has posted an image of a similar phenomenon recorded in New York State in the 19th century:
There's also a photo here of a huge one in Canada, and a video of one in Canada.