A Russian TV crew flying over the Siberian tundra this summer spotted a massive crater 30 meters (100 feet) deep and 20 meters wide -- striking in its size, symmetry and the explosive force of nature that it must have taken to have created it.
Scientists are not sure exactly how the huge hole, which is at least the ninth spotted in the region since 2013, formed. Initial theories floated when the first crater was discovered near an oil and gas field in the Yamal Peninsula in northwest Siberia included a meteorite impact, a UFO landing and the collapse of a secret underground military storage facility.While scientists now believe the giant hole is linked to an explosive buildup of methane gas -- which could be an unsettling result of warming temperatures in the region -- there is still a lot the researchers don't know.
"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."
Permafrost, which amounts to two-thirds of the Russian territory, is a huge natural reservoir of methane, a potent greenhouse gas, and recent hot summers, including in 2020, in the region may have played a role in creating these craters.
Mining a mysteryChuvilin and his team are among the few scientists who have been down inside one of these craters to investigate how it formed and where the gas that causes them comes from. Accessing the craters has to be done with climbing gear and there is a limited window -- the craters turn into lakes within two years of being formed.
The scientists took samples of permafrost soil, ground and ice from the rim of a hole -- known as the Erkuta crater -- during a field trip in 2017 after it was discovered by biologists who were in the area observing falcon nesting. The researchers conducted drone observations six months later.
"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."
The study, which was published in June, showed that gases, mostly methane, can accumulate in the upper layers of permafrost from multiple sources -- both from the deep layers of the Earth and closer 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.
With the Erkuta crater, the scientists' model suggested that it formed in a dried-up lake that probably had something called an underlake talik -- a zone of unfrozen soils that started freezing gradually after the lake had dried out, building up the stress that was ultimately released in a powerful explosion -- a type of ice volcano.
"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.
He said his team will publish more detailed information on the newest crater shortly in a scientific journal. He added it's one of the biggest found so far.