Ice Circles

Are ice circles in Russia what crop circles are in England?:

Astronauts aboard the International Space Station noticed two mysterious dark circles in the ice of Russia’s Lake Baikal in April. Though the cause is more likely aqueous than alien, some aspects of the odd blemishes defy explanation.

The two circles are the focal points for ice break-up and may be caused by upwelling of warmer water in the lake. The dark color of the circles is due to thinning of the ice, which usually hangs around into June. Upwelling wouldn’t be strange in some relatively shallow areas of the lake where hydrothermal activity has been detected, such as where the circle near the center of the lake is located. Circles have been seen in that area before in 1985 and 1994, though they weren’t nearly as pronounced. But the location of the circle near the southern tip of the lake (pictured here) where water is relatively deep and cold is puzzling.