Ice disks or ice circles are created when a thin layer of ice forms over moving water. Underneath the sheet of ice, there is a whirlpool effect in the water, slowly spinning the ice. This will break off a chunk of the ice, but continue spinning the chunk, creating a perfect circle . It is rare to see as it only happens during the winter when it is frigid.
This happened this week on the Presumpscot River in Westbrook, Maine. Last year we had a viewer, Patti, who had an ice disk form in a creek in her backyard in Tyrone!