Gas hydrates contain huge amount of methane gas, and it is destabilization of these that is believed to have caused the craters on the Yamal Peninsula. (cage.uit.no)
It was evidence that the Bakken was leaking raw natural gas, including huge amounts of methane, which is 86 times more potent as a global warmer than carbon dioxide during the first nine years of its life. (scientificamerican.com)