It is not the melting of permafrost that causes giant gas bubbles to erupt, geophysicists found. This crater in Yamal is the 17th such crater that was found in the region.
Vasily Bogoyavlensky, geologist and geophysicist, said that there are many of such "black holes" in the north of Russia. Many of those craters have emerged during the past ten years.
The very first crater, which was discovered in 2014, became the famous one. It was a hole about 50 meters deep and 40 meters in diameter. Geologists quickly established that the giant hole in the ground was just a hole, from which methane was bursting out.
A cavity is formed in the layers of underground ice as it melts due to the influence of a local anomalous heat flow. This cavity is then filled with gas, and it grows larger, causing the surface on the ground to swell until the frozen rock reaches its ultimate strength and eventually explodes in a pneumatic explosion.
Some scientists assumed that the Yamal crater was the first cryovolcano on planet Earth - a volcano that appears in permafrost and spews out jets of gas instead of melted magma. Until recently, such cryovolcanoes were observed only in space - on Neptune's satellite Triton, and on Titan or Enceladus (the moons of Saturn). According to Vasily Bogoyavlensky, the Yamal gas eruptions can be referred to as volcanoes only to a certain degree, although several craters can be defined as such.
"I believe that many of these objects can be categorised as ordinary mud volcanoes, but they have their own peculiarities, because the near-surface soil is frozen. It additionally restrains the gas, and the pressure in the cavity can reach high values. As a result, the gas still breaks through the rock," the researcher said.
Crater 17 is especially interesting because it was possible to see it literally a month after it was formed. In a year or two, these craters get filled with water and turn into lakes, which makes it very hard to find out what they have at the bottom.
On July 16, 2020, Andrey Umnikov, the director of the Russian Center for Arctic Development, saw the giant sinkhole about 25 meters in diameter from a helicopter. In August, scientists from the Institute of Oil and Gas Problems of the Russian Academy of Sciences and the Skolkovo Institute of Science and Technology studied the crater from the inside.
The depth of the crater is about 30-34 meters. The cavity is considerably elongated. Based on the images, received with the help of a drone, the scientists could build a 3D model of C17 and recreate its origin.
The first "Yamal bubble" burst three and a half kilometers from the main gas pipeline, and another one appeared in the vicinity of railway tracks.
On February 28, 2021, the Arktika-M satellite was launched from Baikonur cosmodrome. The satellite, among other things, will help geologists monitor frost mounds from space.
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