The finding is prompting concerns that a new feedback loop that accelerates climate change may have already been triggered.
Locals say they saw flames and smoke as a major bubble of methane blasted below the surface and created another sinkhole in the Russian Arctic peninsula.
Russian scientists in the Arctic Ocean said they have discovered the most powerful methane gas fountain ever recorded, highlighting the danger of this greenhouse gas accelerating climate change or causing an oil or gas spill as it erupts from thawing permafrost.