"It was making noises. It was like something alive." And now there are at least 17 of them. Popular Mechanics reports journalists with Russian news agency Vesti Yamal in July observed a 164-foot-deep crater on the Yamal Peninsula, the 17th such crater to have been found in a northwestern part of Siberia since 2014; they released video of it last week. Scientists believe the craters result from blasts caused by subterranean methane gases. The New York Times' explainer: "Contained beneath a layer of ice above and permafrost all around, the gas creates pressure that elevates the overlying soil. The explosions occur when the pressure rises or the ice layer thaws and breaks suddenly." But the finer details haven't been worked out, like if and how global warming is a contributing factor (probably, per geologist Yevgeny Chuvilin, who visited Crater 17 and spoke of its "noises") and why the blasts aren't happening elsewhere in Siberia or the northern reaches of North America.
And as for how the explosion is triggered, there are two working theories: that an icelike form of methane is reverting to its gaseous state, possibly due to global warming, or that increasingly warm summers are causing the thawing active layer of the permafrost to increase in depth, which could in turn be causing the ice over the gas to weaken. Temps are indeed warming: Popular Mechanics cites National Geographic in reporting that Verkhoyansk, Russia, which sits north of the Arctic Circle, hit a record 100.4 degrees in June. Newsweek reports scientists are now trying to identify "heave mounds," areas where the ground seems to be ballooning, indicating a possible looming explosion. Of the 7,100 heave mounds found on Yamal Peninsula and the adjacent Gydan Peninsula, a Russian scientist says as many as 6% are quite dangerous. (Read more crater stories.)