The massive crater appeared violently and explosively in the Siberian tundra last year -- a powerful blowout of methane gas throwing ice and rock hundreds of feet away and leaving a gaping circular scar in the empty and eerie landscape.
It was the 17th hole to appear in the remote Yamal and Gyda peninsulas in the Russian Arctic since the first was spotted in 2013, mystifying scientists. The craters are thought to be linked to climate change. Drone photography, 3D modeling and artificial intelligence are helping to reveal their secrets.
"The new crater is uniquely well preserved, as surface water hadn't yet accumulated in the crater when we surveyed it, which allowed us to study a 'fresh' crater, untouched by degradation," said Evgeny Chuvilin, lead research scientist at the Skolkovo Institute of Science and Technology's Center for Hydrocarbon Recovery in Moscow.
It was also the first time researchers have been able to fly a drone deep into a crater -- reaching 10 to 15 meters below ground, allowing them to capture the shape of the underground cavity where methane had built up.
Chuvilin was part of a team of Russian scientists who visited the crater in August 2020. Their findings were published in the journal Geosciences last week.
The drone took around 80 images, allowing the researchers to build a 3D model of the crater, which is 30 meters deep -- imagine three buses end to end.
Study author Igor Bogoyavlensky, of the Oil and Gas Research Institute of the Russian Academy of Sciences, served as the drone pilot and said he had to lie down on the edge of the 10-story deep crater and dangle his arms over the edge to control the drone.
"Three times we got close to losing it, but succeeded in getting the data for the 3D model," he said.
The model, which showed unusual grottoes or caverns in the lower part of the crater, largely confirmed what scientists had hypothesized: Methane gas builds in a cavity in the ice, causing a mound to appear at ground level. The mound grows in size before blowing out ice and other debris in an explosion and leaving behind the massive crater.
What's still unclear is the source of the methane. It could come from deep layers within the Earth or closer to the surface -- or a combination of the two.
Permafrost is a huge natural reservoir of methane, a potent greenhouse gas much more effective than carbon dioxide at trapping heat and warming the planet. Warmer summers -- the Arctic is warming two times faster than the global average -- have weakened the permafrost layer, which acts as a cap, making it easier for gas to escape. Some experts estimate that soils in the permafrost region hold twice as much carbon as the atmosphere does, making the region extremely important in the fight against climate change.
"Climate change, of course, has an impact on the probability of gas blowout craters appearing in the Arctic permafrost," Chuvilin said.
With the use of satellite imagery, the researchers were also able to pinpoint when the crater formed. They believe the mound would have exploded at some point between May 15 and June 9, 2020. The crater was first spotted during a helicopter flight on July 16, 2020.
The timing was not random, according to Chuvilin. "This is the time of the year when there's a lot of solar energy influx, which causes the snow to melt and the upper layers of the ground to heat up, and that causes changes in their properties and behavior."
While these craters have appeared in a very sparsely populated region, they do pose risks to Indigenous people and to oil and gas infrastructure. The holes are usually found by accident during helicopter flights or by reindeer herders.
Mapping and predicting crater blowouts
While 17 craters have been documented so far, it's not known how many there are in total or when the next one could blow out.
Scientists don't yet have good tools for detecting and mapping the gas emission craters, although a team at the Woodwell Climate Research Center in Massachusetts is trying to change that.
To log changes in the Arctic landscape, and perhaps ultimately predict where the next blowout crater might occur, the researchers have devised an algorithm to quantify changes to features such as the height of mounds and the expansion or shrinking of lakes on the Yamal and Gyda peninsulas.
The scientists' model correctly predicted all seven craters that had been reported by scientists by 2017 and revealed the formation of three new ones.
The researchers also found that the craters are just one unsettling sign that the northernmost reaches of our planet are undergoing radical changes.
Some 5% of the 327,000 square kilometers the team surveyed saw abrupt changes in landscape between 1984 and 2017. These changes included ground collapses, the formation of new lakes and disappearance of others, plus the erosion of river bends, according to the research, which published in the Geosciences journal in January.
"These craters represent a ... process that was previously unknown to scientists," said Sue Natali, Arctic program director at the Woodwell Climate Research Center and coauthor of the study, in a statement.
"The craters and other abrupt changes occurring across the Arctic landscape are indicative of a rapidly warming and thawing Arctic, which can have severe consequences for Arctic residents and globally."