The mystery of exploding Siberian craters

The mystery of exploding Siberian craters
The mystery of exploding Siberian craters
Anonim

On the distant Yamal Peninsula, located beyond the Arctic Circle, huge wounds began to appear in the permafrost - something happens underground, then something breaks out from the depths to the surface, causing concern for scientists. Russian and American scientists tell about the possible reasons for this phenomenon.

These wounds on the ground appeared suddenly and instantly, after which huge pockmarks remained on the surface.

At the edges of the resulting crater, the soil is a gray and coarse mixture of ice and pieces of permafrost. The roots of plants - they appeared on the surface after the formation of a crater - have traces of combustion on them. This allows us to judge what powerful forces participated in the formation of this hole located in the central part of the Siberian Arctic.

When viewed from the air, the newly discovered bare land is immediately striking against the backdrop of green tundra and dark lakes around it. The layers of earth and rocks that can be seen inside this cylindrical hole are almost black in color, and by the time scientists reached this place, water had already started to accumulate at the bottom.

Among them was Evgeny Chuvilin, a geologist at the Moscow-based Skolkovo Institute of Science and Technology. He flew by plane to this remote corner of the Yamal Peninsula in northwestern Siberia to see the phenomenon. This pit, 50 meters deep, may contain key pieces of the puzzle that have haunted him for the past six years since the discovery of the first such hole elsewhere on the Yamal Peninsula.

This crater (20 meters wide and 52 meters deep) was discovered by a helicopter pilot flying over it in 2014. It happened about 42 kilometers from the Bovanenkovo natural gas field on the Yamal Peninsula. Scientists who visited the site, including Marina Leibman, chief researcher at the Institute of the Earth's Cryosphere (Siberian Branch of the Russian Academy of Sciences), which has been studying permafrost in Siberia for more than 40 years, called what they saw there as a completely new phenomenon in the permafrost region. Analysts who studied satellite images later reported that this gas emission crater (GEC) - called GEC-1 - formed sometime between October 9 and November 1, 2013.

The last of these craters was discovered in August this year by members of a television crew, when they flew over the site with scientists from the Russian Academy of Sciences and local officials during an expedition to Yamal. Thus, the total number of craters found on Yamal and on the neighboring Gydan Peninsula reached 17.

However, the reasons for the appearance of these huge holes in the permafrost, as well as the speed of their formation, remain mysterious. There are also unanswered questions about what they might mean for the future of the Arctic and for the people who live and work there. For many Arctic researchers, the appearance of these dips is a worrying sign, which seems to mean that some radical change is taking place in these cold and sparsely populated areas in the north of our planet.

However, recent research has led to some speculation about what is actually going on there. What is clear is that these holes are not formed as a result of gradual precipitation as the permafrost melts and sinks below the surface. Their education is explosive.

“When an explosion occurs, large chunks of land and ice are thrown hundreds of meters from its epicenter,” Chuvilin says. “We are dealing here with a colossal force created by very high pressure. However, it remains a mystery that this pressure is so high."

Chuvilin is part of a group of Russian scientists - they collaborate with their colleagues around the world - who visit the sites of these craters to collect samples and carry out various measurements. They are trying to better understand what is happening in the depths of the tundra, under its surface.

Some scientists compare these craters to cryovolcanoes - volcanoes that spew out ice instead of lava. It is generally accepted that such volcanoes exist in some remote parts of our solar system - on Pluto, Titan, the moon of Saturn, and also on the dwarf planet Ceres. However, with the accumulation of observations at different periods of their evolution, the resulting holes began to be called "gas emission craters". This name allows you to get some idea of the nature of their formation.

"The analysis carried out on the basis of images obtained with the help of satellites shows that as a result of the explosion, a giant hole is formed in the place of a small mound of heaving," says Chuvilin. These elevations are vaulted, and they are formed at the moment when a layer of frozen soil is pushed to the surface by water, and then the water accumulated there begins to freeze. The resulting ice expands to form a small hill. Such elevations, for which the local Yakut word “bulgunnyakh” is also used in Russian, appears and disappears when the seasons change. However, in much of the Arctic, these heaving mounds ultimately sink into the ground rather than explode.

It is obvious that these elevations in the northwest of Siberia behave differently. According to Chuvilin, they quickly grow and reach a height of several meters, but then their top suddenly explodes. Apparently, it is not freezing water that pushes them to the surface, but the gas accumulating underground.

“These bulges have been forming over time,” says Sue Natali, ecologist and Arctic expert [she studies permafrost and is director of the Arctic Program for the Woods Hole, Massuchusetts Climate Research Center. them. George Woodwell (Woodwell Climate Research Center)]. "These kinds of gas-filled mounds form over the years."

A study of the annual rings of willow branches found among the discarded rock (this happened in 2014 after the explosion and the formation of the first crater) led to the conclusion that these plants have been under stress since the 1940s. Experts believe that this could have happened as a result of soil deformation.

“However, there is evidence that the life cycle of gas emission craters can be very short, ranging from three to five years,” says Alexander Kizyakov, a cryolithologist at Lomonosov Moscow State University. One of the craters formed in the summer of 2017 and known as SeYkhGEC, discovered using a satellite image, first began to form in the soil in 2015.

The same traces and swellings associated with the release of gas pockets were found at the bottom of the Kara Sea, near the Yamal Peninsula, and others in the Barents Sea region. However, so far, according to Natalie, nothing like this has been found on land in other parts of the Arctic.

Some processes associated with permafrost in Yamal and the Gydan Peninsula are the reason for the explosion of such hillocks. “The soil there has certain properties,” she says.- A very thin layer of ice forms there, it is plate ice, which forms a kind of dense upper part of the permafrost. In addition, numerous cryopegs are also formed there, that is, areas of unfrozen soil surrounded by permafrost - we can say that these are a kind of sandwiches. There is also a third characteristic feature - very deeply located oil and natural gas fields”.

One of these craters was recently studied by Chuvilin - the width of its crater is 20 meters, it was named "Yerkuta" after the river, in the floodplain of which it appeared. Apparently, it formed at the bottom of a dry lake. When the lake disappeared, an unfrozen layer of soil remained there, which is called a talik, and it is there that gas begins to accumulate. However, Chuvilin believes that the exact source of the crater formation cannot yet be named. “The main question in the study of the crater is to determine the source of the gas that accumulates under the permafrost,” says Chuvilin. "As soon as a crater appears, there is no more gas there."

Local reindeer herders reported seeing flames and smoke after a crater exploded in June 2017.

At present, issues related to the evolution of these heaving mounds, and also with how gas gets there, are being carefully studied. “It is of great interest that we may be facing a new or previously unknown geochemical process here that we had no idea about before,” Natalie says.

Daring enough explorers descending into such craters found elevated levels of methane there, suggesting that this gas is likely rising from below. One of the leading theories is that methane, located at great depths under the permafrost layer, tries to climb up the unfrozen pockets, as a result of which it accumulates under the ice layer. According to another idea, the high content of carbon dioxide in the water in such defrosted pockets begins to rise upward as the water freezes, and the remaining water is not able to hold the dissolved gas.

In addition to methane and carbon dioxide, craters can also be caused by microorganisms present in unfrozen soil pockets. They decompose organic materials, resulting in the formation of gases, Chuvilin said. Methane isotope analysis at one of these craters appears to support this point of view, but the activity of methane-producing microbes has been found to be extremely low in lakes formed at the bottom of such craters - low even for cold latitudes where they are located.

However, methane can also penetrate directly through ice. The gases can become trapped inside water crystals in permafrost, and then they form rather strange materials known as gas hydrates. When they are thawed, gases are released.

“Perhaps there are other formation mechanisms that are difficult to represent in the form of a single model,” says Chuvilin. "A lot depends on the environment and the nature of the area." At least one crater, he said, was found on the riverbed.

Regardless of the source, we can assume that gases accumulate under unfrozen layers of the earth, begin to lift up a dense crust of ice by 5-6 meters, and then burst like a boil (Although this is a very vivid analogy, it is not so bad, it is very similar netizens who are delighted with videos of people squeezing their pimples, and some scientists are delighted with one kind of Yamal craters. “It was a combination of the unknown and the risk associated with these craters, and this is what attracts me , - Natalie admits).

When these mounds finally explode, the whole thing actually looks quite colorful. The earth and ice on top of these gas-filled pockets, as well as other contents of the unfrozen parts, all rise 300 meters in height after the explosion. The explosion is so powerful that pieces of earth a meter thick rise upward, resulting in a high parapet, a wide mouth and a narrower cylindrical hole near the crater - it is believed that this is an unfrozen pocket. Local reindeer herders say they saw flames and smoke after an explosion on one crater in June 2017 near the banks of the Mydriyakha River. Residents of the nearby village of Seyakha - it is located about 33 kilometers south of this crater - say that the gas burned for almost 90 minutes, and the height of the flame reached 4-5 meters.

After a year or two, the edges of this dark and gloomy wound disintegrate and fill with water.

This region is one of the most sparsely populated on the planet, however, the crater formation so close to the settlement is of concern. The region also has a large number of oil and gas pipelines and other infrastructure elements, all of which are used to extract fossil fuels hidden under the permafrost.

“We don't yet know if this poses a risk to people in the Arctic,” Natalie says. She and her colleagues are trying to answer this particular question and are also looking for other craters using high-resolution satellite imagery.

“Once we find something that looks like a crater, we use a very high resolution time sequence of images, which means we are talking about satellite images taken at different times, and then we try to establish when they formed,” she says. Apparently, the work of these specialists suggests that there are more craters there than was previously thought. “So far, we have identified and confirmed the sites of the formation of two new craters, and there are several more craters, the confirmation of the existence of which we are currently engaged in. We have about two dozen of these craters in the "very likely" category and are currently in the process of checking them out. Given the fact that we knew nothing about them at all in 2013, there may be more. more".

Ultimately, Natalie and her team members hope to collect enough data to automate the search process. Their main goal is to develop an algorithm that would predict the appearance of craters even before they form, and for this, it is necessary to search for gas-emitting frost mounds using images obtained from satellites.

“We hope to achieve a result that will allow us to determine the location of possible craters even before they form,” says Natalie. “The need to obtain information about such processes is especially great in those areas where people live, where pipelines pass, where elements of the oil and gas infrastructure are located.”

Trying to establish how common these craters are is a slow process. After a violent process of formation, most of them disappear almost as quickly. For example, the hole formed after the explosion near the village of Sayakha - 70 meters wide and more than 50 meters deep - was filled with water just four days later, which was caused by the proximity of the river. This kind of transformation of a hole into a lake can be considered a rather harmless ending to such a dramatic phenomenon.

Other craters fill with water more slowly, but after a year or two, the sharp edges of this dark and gloomy wound collapse, fill with water and become almost indistinguishable from the thousands of other small circular lakes - they are called thermokarst lakes - scattered throughout the area. It is not yet clear which of these are scars reminiscent of gas emissions.

“It is possible that some of these lakes in the permafrost zone are craters filled with water,” says Kizyakov. "It is too early to say how common the mechanism of lake formation is."

Some experts are trying to identify the lakes caused by the release of gas by analyzing the chemicals in the water, but so far they have not been able to identify any general patterns.

Attempts to determine how frequent such events are is not just a matter of curiosity. There is growing concern that the emergence of such craters in northwest Siberia may be related to wider changes occurring in the Arctic due to climate change.

Surface temperatures in the Arctic are rising at twice the global average, and this is causing large amounts of permafrost melting in the summer months.

This alone is already changing the Arctic landscape and leads to soil subsidence and landslides, which are called thaw slumps. Siberia seems to have the largest number of such landslides on the planet - the largest of them is the Batagayk Basin - at first, in the 1960s, there was only a small ravine, and now the width of this crater is 900 meters.

“As far as I know, nowhere on the planet is climate change causing such a change in the physical composition of the soil,” says Natalie.

Hidden under the Arctic permafrost is a huge amount of carbon - roughly double what is currently in the Earth's atmosphere. For the most part, these are frozen remains of animals and other organic materials, as well as the methane trapped inside these ice crystals - these are the gas hydrates that Chuvilin spoke about earlier. When the soil on the surface thaws, it allows microorganisms to break down organic matter, and as a result, methane and carbon dioxide are formed as a by-product of this process, while the methane contained in the ice mass also breaks free.

A potent greenhouse gas, this methane escaping from under the layers of permafrost has the potential to accelerate global warming and thus cause further melting.

In Yamal, however, the craters suggest another process is promising, adding even more uncertainty to a complex feedback loop between rising temperatures, melting permafrost and greenhouse gas emissions. If it turns out that methane that has accumulated deep below the permafrost layer begins to seep out through the usually impenetrable layers of permafrost, this could be a signal that the frozen ice crust above the tundra surface is becoming more permeable. This could mean even more uncertainty about how changes in the Arctic will affect wider global warming on our planet.

“These craters are very shocking evidence of what is happening in the Arctic more broadly,” Natalie says. - If you look at the changes that are taking place in this entire region, then some of them occur gradually, while others - suddenly. Very few of them are explosive, but all this makes us pay attention to how they all contribute to an increase in emissions of greenhouse gases into the atmosphere”.

While experts have yet to unravel the mystery of the Yamal craters, it can already be concluded that we probably need to keep a close eye on them in the future.

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