For the first time, geologists used an aerial drone to map the interior of a giant explosion crater, the kind that appeared with increasing regularity in Siberia.. The resulting 3D model, along with other data collected during the research, is reinforcing the prevailing theory linking these bizarre holes in the tundra increase the heat.
“Over the years, we have gained a lot of experience with surveillance drones, but this underground aerial survey of the C17 crater was the most difficult task I have ever faced, having to lie on the edge of a 10-story deep crater and wave my arms to control the drone, ”said Igor Bogoyavlensky, a geologist at the Russian Academy of Sciences Oil and Gas Research Institute, in a demonstration.
Bogoyavlensky said he was close to losing the drone on three occasions, but “managed to get the data for the 3D model”, the details of which have now been Published in Geosciences magazine.
Andrey Umnikov, co-author of the study and director of the Russian Arctic Development Center, was the first to locate C17 what he did from a helicopter in July 2020. The depth of 98 feet (30-meters deep) hole is located on the Yamal Peninsula, in northwest Siberia, and is located near three other rupture craters, including the Yamal crater, whose sudden appearance alerted the world to this strange phenomenon in 2014. The one that researchers are studying opened last summer In between record heat.
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The theory behind these craters, of which 20 are known, is that they are the result of melting permafrost. As the Arctic heats, gas, mainly methane, accumulates within the cavities located in the upper layer of permafrost. Eventually, the soil is no longer able to contain this pressure and emits a powerful burp in the form of a gas explosion, throwing out the material (ejected) and forming a crater, according to this view. The explosion holes do not last long, as they quickly fill with water and turn into lakes.
Hence the urgency to organize an expedition to study the C17 in detail, and to do it as soon as possible after its discovery. The team, which included experts from the Skolkovo Institute of Science and Technology, visited the hole in August. 26 2020 – approximately 40 days after first detection.
Upon arrival, the team realized that the hole had slightly increased in size, resulting from the melting and collapse of the rock. The measurements showed that the depth of the hole was not uniform, ranging from 29 to 33 meters (95 to 108 feet) in depth.
“The new crater is impressive in its ideal state of preservation, especially the cone-shaped top from which the ejected material was launched, the outer parts of the hill that precipitated the crater, the walls of the crater itself that are incredibly well preserved and, of course, the gas cavity in the icy bottom of the crater, ” Evgeny Chuvilin, co-author of the study and scientist at the Skoltech Center for Hydrocarbon Recovery, said.
Pieces of ejected material were seen up to 220 meters from the crater, highlighting the force of the explosion.
It is important to note that the team arrived in time to find the hole in “almost untouched state” and “without water to fill it,” said study co-author Vasily Bogoyavlensky. At the same time, the icy dome remained largely intact. Before the explosion, the cavity contained a circular dome with an elliptical bottom, explained Bogoyavlensky, to whom he added: “As far as we know, we can say that the C17 crater is linked to … deep fault [tectonics] and an anomalous terrestrial heat flow. ”
Igor Bogoyavlensky piloted the aerial drone, marking the first time that a drone was used to search for an explosion crater. It was also the first opportunity for scientists to study a relatively new crater that did not collapse or fill with water. (Sscientists have climbed into these things before, but only afterwards mainly filling with water.) The drone, which reached a depth of 50 feet (15 meters), collected valuable data, allowing the team to build a 3D model of the interior of the crater. The researchers also documented features not visible on the surface, such as caves and a suspected cave at the bottom.
According to the 3D model, the crater has a diameter of about 82 feet (25 meters), while the gas cavity at the bottom measures between 43 to 49 feet (13 to 15 meters) wide. The gigantic piece of dirty ground ice in the crater measures 23 meters thick in some places. The total volume of underground space is estimated at 353,000 cubic feet (9,910 cubic meters), including about 265,000 cubic feet (7,500 cubic meters) of ice.
The team also analyzed remote sensing data collected by helicopters and satellites, the last of which showed that the C17 hole formed somewhere between May 15 and June 9th of last year. Search published earlier this month used satellites to discover even more holes in the tundra too.
Together, these observations strengthen the theory about how these holes are created: The constant accumulation of gas inside an underground cavity leads to tremendous pressures, leading to the formation of a “perennial lift pile”, or PHM, according to the study. If the growth of a PHM reaches a critical limit, a volcanic-like explosion occurs, forming a large crater.
“The specific shape of the underground cavity in solid ice, whose structure is represented by a 3D digital model, is of great importance for the factual confirmation of the cavity formation model”, wrote the authors in the article. “This proves the model of its formation in massive crushed ice, the gas-dynamic mechanism of PHM formation and the powerful gas blowout with the destruction of the arc part of the underground cavity and the PHM itself.“
Looking ahead, scientists hope to learn more about the gas and where it comes from, how it accumulates inside cavities and how it can result in such a powerful explosion. The team hopes to revisit the opening of the C17 later this year to continue their investigation of this curious natural phenomenon with a man-induced twist.