Late in April 2009, astronauts aboard the International Space Station observed a strange circular area of thinned ice in the southern end of Lake Baikal in southern Siberia. The ice ring had a diameter of 2.7 miles (4.4 km). Credit: NASA
Methane emissions can create a rising mass of warm water
that begins swirling in a
circular
pattern because of the Coriolis force, or the phenomenon caused by the
Earth's rotation that also helps create cyclones.
Once the water mass reaches the underside of the ice
on the surface of the lake, the warm water melts the ice in a ring shape,
The latest ring patterns included a circle of thin ice with
a diameter of 2.7 miles (4.4 km), although the circular patch was becoming a
hole of open water. Astronauts spotted similar ice circles in both 1985 and
1994, and satellites have also made sightings over the past years.
This phenomenon is nothing new to the Russian government,
which has documented circle sightings on an official Ministry of Natural
Resources Web
clipped from: www.livescience.com 
