https://youtu.be/06Xc3LtZRWo
Back in 2016, local environmental researchers Alexander Sokolov and Dorothee Ehrich decided to pull back the dirt and grass that had been blanketing these bulging bumps of earth, and found that the air escaping from them contained up to 1,000 times more methane than the surrounding air, and 25 times more carbon dioxide.
And things can get even weirder at the bottom of the biggest sinkholes – a 2014 investigation into a 30-metre-wide (98-foot) crater on the Yamal Peninsula found that air near the bottom of the crater contained unusually high concentrations of methane – up to 9.6 percent.
As Katia Moskvitch reported for Nature at the time, archaeologist Andrei Plekhanov from the Scientific Centre of Arctic Studies in Salekhard, Russia, told her that the surrounding air usually contains just 0.000179 percent methane.
Source: http://www.sciencealert.com/7-000-huge-gas-bubbles-have-formed-under-siberia-and-could-explode-at-any-moment