A series of nine massive craters have appeared in the Siberian tundra since 2013. Reaching up to a hundred feet deep and 30 meters across, these holes have baffled scientists as to how they appeared. Scientists currently believe that the sinkholes were created from the explosive buildup of methane gas, possibly due to warming temperatures in the region. Permafrost, which amounts to two-thirds of the Russian territory, is a huge natural reservoir of methane, a potent greenhouse gas.
"Right now, there is no single accepted theory on how these complex phenomena are formed," said Evgeny Chuvilin, lead research scientist at the Skolkovo Institute of Science and Technology's Center for Hydrocarbon Recovery, who has visited the site of the newest crater to study its features.
"It is possible they have been forming for years, but it is hard to estimate the numbers. Since craters usually appear in uninhabited and largely pristine areas of the Arctic, there is often no one to see and report them," Chuvilin said.
"Even now, craters are mostly found by accident during routine, non-scientific helicopter flights or by reindeer herders and hunters."
Chuvilin and his team descended the Erkuta crater in 2017 to take samples of permafrost soil, ground and ice from the rim of a hole. They followed up later with drone surveys of the region.
"The main issue with these craters is how incredibly fast, geologically, they form and how short-lived they are before they turn into lakes," Chuvilin said. "Finding one in the remote Arctic is always a stroke of luck for scientists." Their findings, which were published in June, showed that methane gasses clustered close to the surface. The accumulation of these gases can create pressure that is strong enough to burst through the upper layers of frozen ground, scattering earth and rocks and creating the crater.
"We want to stress that the studies of this crater problem are in a very early stage, and each new crater leads to new research and discoveries," he said.
"Cryovolcanism, as some researchers call it, is a very poorly studied and described process in the cryosphere, an explosion involving rocks, ice, water and gases that leaves behind a crater. It is a potential threat to human activity in the Arctic, and we need to thoroughly study how gases, especially methane, are accumulated in the top layers of the permafrost and which conditions can cause the situation to go extreme," Chuvilin noted. Cryosphere refers to portions of Earth's surface where water is in solid form -- ice.
"These methane emissions also contribute to the rising concentrations of greenhouse gases in the atmosphere, and climate change itself might be a factor in increasing cryovolcanism. But this is still something that needs to be researched," Chuvilin said.
"There's been a series of anomalously warm summers in the Arctic. You can imagine that weakening the permafrost layer. Think of it like a cap, if you're thawing this cap, it's making the cap a little bit looser, promoting the ability of the ground to explode," Susan Natali, the Arctic program director at the Woodwell Climate Research Center, who is using satellite data to try to identify and map craters that haven't been seen with human eyes, said.
"It's like with hurricanes. It took a long time for scientists and papers to come out to say yes, climate change is causing hurricane storms to be stronger. There's so few of these holes so it might be tricky to say for certain, but I'm pretty confident climate change is playing a role in this."