What causes the appearance of pond circles?

This is not the technical answer you requested, but none of the qualitative mechanisms suggested in the article seems very plausible, at least not to me. read more

In this case that you pointed out I suspect that the cause of the dark circles was artificial rather than natural. There is a comment on the following link which seemed to me very interesting given the appearance of these 'pond circles' which look rather like clear dark ice, surrounded by white opaque ice, possibly full of air bubbles. read more

Scientists say warm water from the bottom of the pond is likely the cause Some speculate that ducks, fish or aliens were responsible The appearance of mysterious giant circles on an ice-covered pond has some upstate New York residents wondering if they've been visited by beings from another realm. read more

Mysterious pond circles appeared in an upstate New York pond. Credit: Peggy Gervase In the small town of Eden, N.Y., the recent appearance of mysterious circles in a frozen pond has residents baffled. read more