its not a gas blow out or a sinkhole. Its a pingo. its formed by frozen water underground slowly pushing up over thousands of years. hence, the smooth sides with what looks like tool marks, its similar to the effect of glaciers sliding over the ground. The ice that formed it has since melted and drained away, which is why they blame it on global warming.
Potentially factual info on ODT? Dunce him!
Researching now.

