(CNN) -
A Russian television crew flying over the Siberian tundra this summer saw a massive crater 30 meters deep and 20 meters wide, surprising for its size, symmetry, and the explosive force of nature it must have taken to create it.
Scientists are unsure exactly how the huge hole was formed, which is at least the ninth discovered in the region since 2013. Initial theories floated when the first crater was discovered near an oil and gas field on the Yamal Peninsula. in northwestern Siberia, including a meteorite impact, a UFO landing, and the collapse of a secret underground military storage facility.
While scientists now believe that the giant hole is linked to an explosive buildup of methane gas, which could be a disturbing result of warming temperatures in the region, there is still a lot that researchers don't know.
In August 2020, the RAS Institute for Oil and Gas Problems, supported by the local Yamal authorities, carried out an expedition to the new crater.
Credit: Evgeny Chuvlin.
"At this time, there is no single accepted theory about how these complex phenomena form," said Evgeny Chuvilin, senior research scientist at the Skolkovo Institute of Science and Technology Hydrocarbon Recovery Center, who has visited the crater site more. again to study its characteristics.
“They may have been in the making for years, but it's hard to estimate the number.
Since craters often appear in uninhabited and largely unspoiled areas of the Arctic, there is often no one to see or report them, ”said Chuvilin.
"Even now, the craters are mostly found by accident during routine unscientific helicopter flights or by herders and reindeer hunters."
Permafrost, which is equivalent to two-thirds of the Russian territory, is a huge natural reserve of methane, a potent greenhouse gas, and the recent hot summers in the region, including in 2020, may have played a role in creating these. craters.
The Yamal crater was the first to be discovered in the region.
It was found in 2013.
Mining a mystery
Chuvilin and his team are among the few scientists who have been inside one of these craters to investigate how it formed and where the gas that causes them comes from.
Access to craters must be done with climbing gear and there is a limited window: craters turn into lakes within two years of their formation.
Scientists took soil and ice samples from permafrost 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 hawk nesting.
The researchers conducted drone observations six months later.
"The main problem with these craters is how incredibly fast, geologically, they form and how short they are before turning into lakes," Chuvilin said.
"Finding one in the remote Arctic is always a stroke of luck for scientists."
An investigator climbs into the Erkuta crater.
The study, which was published in June, showed that gases, primarily methane, can accumulate in the upper layers of permafrost from multiple sources, both deep within the Earth and closer to the surface.
The build-up of these gases can create a pressure strong enough to break through the upper layers of frozen soil, scattering dirt and rocks and creating the crater.
"We want to emphasize that studies of this crater problem are at a very early stage, and each new crater leads to new research and discoveries," he said.
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We may have finally found the crater
With the Erkuta crater, the scientists' model suggested that it formed in a dry lake that likely had something called talik underneath the lake, an area of unfrozen soils that gradually began to freeze after the lake had dried up, increasing the stress that was finally released in a powerful explosion, a type of ice volcano.
“Cryovolcanism, as some researchers call it, is a very little studied and described process in the cryosphere, an explosion that involves rocks, ice, water and gases that leave a crater.
It is a potential threat to human activity in the Arctic and we need to study in depth how gases, especially methane, accumulate in the upper layers of the permafrost and what conditions can make the situation extreme, ”Chuvilin said.
The cryosphere refers to portions of the Earth's surface where water is in a solid form - ice.
'These methane emissions also contribute to increased concentrations of greenhouse gases in the atmosphere, and climate change itself could be a factor in the rise of cryovolcanism.
But this is still something to be investigated, ”said Chuvilin.
He said his team will publish more detailed information on the newest crater shortly in a scientific journal.
He added that it is one of the largest found so far.
Extreme summers
Marina Leibman, a Russian permafrost expert at the Earth Cryosphere Institute of the Russian Academy of Sciences, was part of a team of researchers that has analyzed five gas emission craters using remote sensing data and field studies.
The researchers found that the craters shared some similar characteristics, most notably a 2- to 6-meter-high mound that formed before the explosion.
The craters were also located on gentle slopes and had a bottom that was cylindrical like a can before opening into a funnel, with an opening diameter between 20 and 25 meters wide.
All the explosions ejected ice from the ground, in some cases leaving holes where huge frozen blocks have fallen to the surface.
Leibman believed that the extremely hot summers in the region in 2012 and 2016, and again this year, may have played a role in the growth and explosion of these mounds.
The mounds appear and explode in as little as three to five years.
“The release of methane from permafrost… is probably caused by the increase in air and soil temperatures during the last decades.
The formation of all GECs (gas emission craters) was preceded by abnormally warm summers, ”according to the study, which was published in July this year, he said.
He said methane accumulates in a feature known as cryopeg, a layer of unfrozen soil that never freezes due to its salt content under a table of crushed ice, and acts as a trap.
The gas then escapes, deforming the ice and soil, to form a mound.
And when the heat "hit" during a hot summer, the mounds exploded, creating the spectacular craters.
Leibman believed that the craters are likely unique to this Arctic area because few other areas share the characteristics she believes are necessary for the holes to form: a combination of mesa-like land ice near the surface, continuous permafrost. saturated with methane and unfrozen soil with saline deposits under the ice.
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Neither feature has been discovered or reported in the Arctic of Alaska or Canada, according to Susan Natali, director of the Arctic program at the Woodwell Climate Research Center, who is using satellite data to try to identify and map craters that have not been seen with human eyes.
"Those that have been found are all in this one region of Siberia: the Yamal and Gyda peninsulas," he said.
When Natali first heard about these craters, she noted, “It seemed crazy, but they sure are real.
People haven't seen that many, but they are happening and they continue to happen.
Climate change
Very few people have witnessed any of these explosions, but they pose a risk to people living in these remote regions and the oil and gas infrastructure, said Vasily Bogoyavlensky, a professor at the Institute of Oil and Gas Research at the Academy of Sciences of the United States. Russia.
He spoke with a reindeer herder who witnessed the massive explosion of a mound in a river channel on the Yamal Peninsula in 2017.
"Every morning she went to this little frozen mound in the river because it was the highest place and she was looking where her reindeer were, and this morning when the explosion happened she came back and she started to feel something in her legs and she was afraid and ran" .
“When she was in the distance, 200 or 300 meters, there was an explosion.
I could have died, ”she said.
Other craters have formed within 3 kilometers of railways and an oil pipeline, he added.
Bogoyavlensky is not convinced that the main cause of these craters is warming temperatures linked to climate change.
The villages and herder communities you have spoken with have told you that older generations have shared stories of explosions that created craters in the tundra.
He said the "main input" is gas that tries to move to the surface from deep layers of the Earth.
Leibman said his team has performed laboratory tests on methane from some of the craters and does not believe the gas is coming from deep in the ground.
'Our team and others did laboratory tests of the crater's methane.
Its isotopic composition proves that this methane did not come from deep sources, "he said in an email.
"It is difficult to exclude extremes of air temperature because the first set of craters appeared after the extreme (summer) of 2012, the other after the extreme of 2016 and the newest after the extreme of 2020. Nothing in between," he also said.
August 2014.
Similarly, Natali said she believed climate change plays a role, although more data is needed to say so definitively.
'There have been a number of abnormally warm summers in the Arctic.
One can imagine that weakens the permafrost layer.
Think of it as a limit, if you are unfreezing this limit, you are loosening the limit a bit, promoting the ability of the ground to exploit, "he said.
It's like hurricanes.
It took a long time for scientists and papers to come out and say that yes, climate change is causing hurricane storms to be stronger.
There are very few of these holes, so it might be hard to say for sure, but I'm pretty sure climate change is playing a role in this. '
Siberia
