Ice Discs

Found these "ice discs" (for want of a better term) in a small stream flowing by The Violet Barn in Naples, NY.  The water is on it's way to Canandaigua Lake.  The little cluster of 7 discs at the center of the picture is particularly interesting.  There appears to be a small one forming in the foreground.  I think these were formed as the bits of foam from the little waterfall to the right out of the picture began to freeze with more foam freezing at the edge as the current swirls around.  The discs are about 6" to 10" across?

Evidently there are rarely very large ice discs formed.  You can Google "ice discs" for some more pics, or click here for a nice pic of a big one.