Approaching the mysterious Siberian giant pit

The newly discovered pit is 5 meters below the frozen soil, which is the largest pit ever discovered.

Photography: EVGENY CHUVILIN

Author: MAYA WEI-HAAS Recently, when a Russian TV crew flew over the Siberian tundra, they found a magical scene: a pit appeared on the frozen soil, covering an area of more than half a football field. Ice and mud were thrown out of deep scars on the surface of the earth hundreds of meters away from the pit. In recent years, many such strange pits have been found in the Siberian Arctic, the first one appeared in 214, and this time it was the latest one. Scientists believe that they are formed by the explosion of methane and carbon dioxide trapped in soil and ice, and this phenomenon may become more and more common with the warming of the climate. But there are still many uncertainties. "We still don't know what happened," said Sue Natali, a permafrost expert at the Woodville Climate Research Center in falmouth, Massachusetts. "Will this happen elsewhere?" The recent research on other pits points to a possible mechanism: ice and fire mountain, which erupts frozen mud or snow mud instead of hot lava. This phenomenon is common on other planets in the solar system, such as Saturn's icy moon Enceladus. But ice and fire mountains are rare on earth. By studying the pits in Siberia, we may know what is happening in those distant worlds.

Soon after the pits were discovered, researchers began to investigate, hoping to learn more about how they were formed.

Photography: EVGENY CHUVILIN

More importantly, their findings highlight that we still have too many unknowns about the blue earth, especially as scientists continue to deal with the consequences of climate warming. "It may even happen that we never thought of," Natali said. "Maybe a lot of things have happened, but our knowledge is limited."

Visitors from the Arctic

In July 214, people discovered the first Siberian pit, and there are different opinions about how it was formed. Meteor impact? Missile explosion? Aliens?

After that, the researchers found 15 pits suspected to have been formed by natural explosion. Evgeny Chuvilin, a permafrost expert at the Scholte Hydrocarbon Recovery Center, said that the recently discovered No.17 pit may be the largest one to date. However, it is not easy to study the pits in the Arctic. In the months to years after the explosion, the pits were full of water and hid among many local lakes.

After discovering this pit, Chuvilin and his colleagues immediately went to collect samples. This pit is located in Yamal Peninsula in the northwest of Siberia. Against the gray, yellow and green background of the tundra, it looks "a bit like an outsider". Chuvilin said, "You will be shocked by its size at first." On the nearly vertical inner wall, slowly melting soil falls into the depths and makes a sound-"it gives people a feeling that there is a living thing," he said.

Chuvilin told us in an email that the team is now "urgently processing" these samples and preparing to publish the research results in scientific journals.

Researchers hope to not only better understand the process behind the explosion, but also predict the future location. Andrey Bychkov, a geochemist at lomonosov State University in Moscow, has been studying pits, but has not explored this new one. He said that the explosion may pose a threat to the local people. Some people said that they heard the explosion near the new pit and saw the flames. In 217, it was alleged that a pit exploded near the camp of reindeer herders in Nenets. A large number of local oil and gas infrastructure may be affected.

Raw materials for ice explosion

By analyzing other pits, including sampling the ice wall, we can get some clues. In 218, Bychkov and his colleagues put forward the view that these explosions are a kind of ice and fire mountain, and its center is composed of gas, ice, water and mud, which is explosive.

Permafrost covers 23.3 million square kilometers of land in the northern hemisphere. It is usually frozen all summer, and pits are formed inside the permafrost. They seem to start from the deep unfrozen layer, that is, the "talik". The intermediate frost-free layer is often formed at the bottom of the lake, and the water above heats and isolates the land below. However, as the surrounding permafrost freezes and melts, the lake is constantly changing, usually full of water or completely drained. Once the lake is drained, the ground will begin to freeze.

Katey Walter Anthony, an ecologist at the University of Alaska at fairbanks, said, "It will refreeze from the bottom, sides and top, that is, from all directions." Because the volume of ice is larger than that of water, with the increase of ice, unfrozen mud is constantly squeezed, and gas and water are brought together under pressure, and finally a hill with a swollen surface and warts is formed, that is, an ice core mound.

Natali pointed out that not all pits are related to lakes. Under other conditions, an intermediate unfrozen layer will also be formed, such as underground areas with high salinity, and the freezing temperature of water will be reduced. Some intermediate unfrozen layers will be continuously replenished by rising groundwater.

There are more than 11, frozen layers in the northern hemisphere, which are common in the Arctic. But the explosion that forms the pit seems to be much rarer. People have only seen such pits in Yamal Peninsula and Jidan Peninsula in Siberia, and these explosions require an excessive raw material: gas.

Western Siberia is rich in natural gas, some of which are released along cracks and porous areas and infiltrated into the paste-like interlayer. There are other possible sources of gas. Microorganisms devour organic matter and release methane or carbon dioxide. Methane hydrate in crystalline form will also produce gas after decomposition.

"More than one thing may have happened," Natali said. Different mounds produce slightly different gases, but these gases all play the same role: pressurization. Finally, whether because of the increasing gas pressure or the unstable ice cap covered on it, the whole system suddenly collapsed in the big bang, spraying mud out of the ground, leaving a pit with steep edges.

"It's like opening champagne," Bychkov said.

Relationship with climate and other factors

Studying these explosions may help scientists solve the mystery of ice explosions on other celestial bodies in the solar system. Lynnae Quick, a planetary geophysicist at NASA Goddard Space Flight Center, specializes in ice volcanoes. She told us that the pits in Siberia are very suitable for simulating the activities of ice volcanoes on the dwarf planet Ceres. Unlike many frozen worlds with ice volcanoes, Ceres and the North Pole have some of the same components.

"Ceres is interesting because some rock and soil components are involved in these processes, but other icy satellites are not," Quick said. "We are still trying to figure out the situation there."

The problems of Siberian pits are also unsolved, such as their relationship with climate change. In recent years, the Arctic has experienced many abnormal high temperatures. Just this summer, on June 2th, the temperature in the Russian town of Vikoyansk was as high as 38 degrees Celsius, which was the highest since records began in 1885.

These pits seem to be increasing since they were discovered in 214, but Walter Anthony said that this phenomenon can be traced back to thousands of years ago, and we only noticed it recently. There are more and more flights flying over this area, and the population of Yamal Peninsula is increasing rapidly. "Now, there are railways and big towns here," Bychkov said.

However, as the temperature rises, explosions may become more frequent, because melting will make the ice cap above the gas unstable, which will lead to explosions. Melting will also increase the connection between the ground and the ground, forming a "chimney", through which the gas in the deep underground can more easily penetrate into the intermediate unfrozen layer, Walter Anthony added.

In the process of releasing a large number of greenhouse gases, methane and carbon dioxide released by each explosion may be negligible. But Walter Anthony said that the explosion was just "a moment in a long-term phenomenon".

Climate change has affected the Arctic, where the rate of warming is at least twice as fast as that of other places on the earth. Every year, thicker and thicker permafrost rich in carbon is melting, and in some places, even in winter, the ground will not freeze again. Melting causes microorganisms to swallow once frozen organic matter and release carbon dioxide or methane. This will bring more serious consequences. Permafrost is like a lid, which prevents methane gas stored deep underground from being released into the sky too quickly, Walter Anthony explained. As the permafrost melts, there are more and more holes in the cover, and methane will escape from the surface.

Walter Anthony studied this phenomenon in Arctic lakes. He pointed out that the recent study on the formation of pits may further prove that the gas deep underground has surged to the surface. "Permafrost is like changing from a piece of cheddar cheese to Swiss cheese with more holes."

"This is an uncertain factor in climate change."

(translator: Sky4)