From the Daily Mail:
New unexplained holes have appeared in Siberia following the mystery over a giant crater on the Yamal Peninsula.
A second is in the same permafrost region of northern Russia, and a third on the Taymyr Peninsula, to the east, in Kransoyark region. Both were spotted by reindeer herders who almost fell in.
... One theory is that the feature is a ‘pingo,’ reports the Sunday Morning Herald.
A pingo is a large chunk of ice that is located underground that can create a hole in the ground when it melts.
‘Certainly from the images I’ve seen it looks like a periglacial feature, perhaps a collapsed pingo,’ Dr Chris Fogwill of the University of New South Wales said.
‘This is obviously a very extreme version of that, and if there’s been any interaction with the gas in the area, that is a question that could only be answered by going there.’
Dr Plekhanov added the hole was most likely the result of a 'build-up of excessive pressure' underground, due to the region's changing temperatures.
He said 80 per cent of the crater appeared to be made up of ice and that there were no traces of an explosion.
The discovery eliminates the possibility that a meteorite had struck the region.The holes are 98 ft, 49 ft, and 13 ft in diameter, respectively.