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.
Researchers have hypothesised that these methane bubbles are linked to a recent heatwave that had prompted the Siberian tundra’s permafrost to thaw.
Siberia’s permafrost has become famous for its ability to keep things perfectly preserved for thousands of years, such as this amazing 12,400-year-old puppy, or these adorable lion cubs, which still had their tawny fur coats on after 30,000 years.
A 2013 study found that a global temperature rise of 1.5°C would be enough to kickstart an unprecedented period of melting, but thanks to abnormally hot summers linked to climate change, local researchers suspect that this is already starting to occur, with daily temperatures in July 2016 hitting a worrying 35°C (95°F).