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New explanation for Siberia’s mystery craters

More new mystery craters reported in Russian media last month. A Russian scientist calls for “urgent investigation.” Other scientists suggest a new cause.

B1 - famous Yamal hole in 30 kilometres from Bovanenkovo, spotted in 2014 by helicopter pilots. Pictures: Marya Zulinova, Yamal regional government's press service, via Siberian Times

B1 – famous Yamal hole in 30 kilometers from the Bovanenkovo gas field, spotted in 2014 by helicopter pilots. Photo by Marya Zulinova, Yamal regional government’s press service, via Siberian Times

In mid-July 2014, a mysterious hole in permafrost, spotted by helicopter pilots in the Yamal region of northern Russia, captured the world’s attention. Reindeer herders reported a second hole some days later, and still later a third Siberian crater was found. Weird explanations ranged from meteorites to stray missiles to aliens, but by late July a team of scientists reported that they had measured unusually high concentrations of methane inside the first crater, which is now known as B1. The journal Nature published a story on its website on July 31, 2014 featuring those findings, and many accepted the unsettling idea that an explosive release of methane, related to global warming, caused the craters … until February 2015 when the Siberian Times reported more craters in Siberia. A Russian scientist speculated that there may be “20 to 30 craters more.” The report of more craters has led scientists to offer a different, simpler explanation for them, one that is still related to global warming, but does not involve a powerful and explosive methane release.

Siberian Times wrote on February 23, 2015 that:

Examination using satellite images has helped Russian experts understand that the craters are more widespread than was first realized, with one large hole surrounded by as many as 20 mini-craters …

Moscow scientist Vasily Bogoyavlensky – deputy director of the Moscow-based Oil and Gas Research Institute, part of the Russian Academy of Sciences – called for “urgent investigation” of the craters. He was quoted in Siberian Times as saying:

We know now of seven craters in the Arctic area. Five are directly on the Yamal peninsula, one in Yamal Autonomous district, and one is on the north of the Krasnoyarsk region, near the Taimyr peninsula.

We have exact locations for only four of them. The other three were spotted by reindeer herders. But I am sure that there are more craters on Yamal, we just need to search for them … I suppose there could be 20 to 30 craters more.

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A Russian scientist prepares to descend into a mystery crater in Siberia in November. More holes have since been found.  PHOTOGRAPH BY VLADIMIR PUSHKAREV, THE SIBERIAN TIMES

In this photo, from November 2014, a Russian scientist prepares to descend into one of Siberia’s mystery craters. Since then, scientists have reported a total of seven craters, with dozens more possible. Photo by Vladimir Pushkarev, via Siberian Times.

Four arctic craters: B1 - famous Yamal hole in 30 kilometres from Bovanenkovo, B2 - recently detected crater in 10 kilometres to the south from Bovanenkovo, B3 - crater located in 90 kilometres from Antipayuta village, B4 - crater located near Nosok village, on the north of Krasnoyarsk region, near Taimyr Peninsula.  Image by Vasily Bogoyavlensky via Siberian Times.

Four Arctic craters, all found within the past year. B1 is the famous Yamal hole, 30 kilometers from the Bovanenkovo gas field, a natural gas field located in the Yamalo-Nenets Autonomous Okrug region of Russia. B2 is a recently detected crater 10 kilometers south of Bovanenkovo. B3 is located in 90 kilometers from the village of Antipayuta. B4 is located near Nosok village, on the north of Krasnoyarsk region, near Taimyr Peninsula. Image by Vasily Bogoyavlensky via Siberian Times.

Carolyn Ruppel, chief of the U.S. Geological Survey’s Gas Hydrates Project, told EarthSky this week (March 9, 2015) that an explosive release of methane is not a likely explanation for the craters. It’s true that, in Siberian permafrost, large deposits of methane gas are trapped in ice, forming what is called a gas hydrate. Methane remains stable and frozen at certain temperatures, but as the permafrost warms, and its internal strength decreases, it may be less able to withhold the build-up of sub-surface gases, and thus a release of methane is possible.

But, Ruppel told us:

Generic methane hydrates in permafrost settings are normally not stable above about 200 meters depth. The craters are far shallower than that, so tapping into dissociating methane hydrate is probably unlikely.

She and other scientists are calling on a simpler explanation, related to mounds of earth-covered ice in the Arctic and subarctic known as pingos.

National Geographic reported on February 27:

A pingo is a plug of ice that forms near the surface over time and has a small mound or hill on top.

When an ice plug melts rapidly — as many have been, thanks to unseasonably warm temperatures in Siberia over the past year — it can cause part of the ground to collapse, forming a crater.

That can’t be the whole story, since ejected rocks that have been found around the rim of the craters, suggesting some sort of explosion.

Satellite images showing pingo before the gas emission on the object B2 (top). Lake formed here at the place of the number of craters and the network of more than 20 'baby' craters around (bottom). Photos via: Vasily Bogoyavlensky and Siberian Times.

This pair of images – which I believe is the crater B2 – came from Vasily Bogoyavlensky and Siberian Times. At top, an older satellite image shows a pingo (top) where the crater is today. At bottom, the crater has filled with water and become a lake, and a network of more than 20 ‘baby’ craters surround it.

Plus, if explosive methane release is not the reason for the craters – as reported last summer – what can account for the unusually high concentrations of methane reported with the first crater, B1? Carolyn Ruppel told EarthSky:

This part of Siberia does have a lot of methane in terms of underlying conventional gas deposits. So it is possible that these craters are somehow tapping into some migration pathway for those gas deposits…

More generically, permafrost and thawing permafrost are sometimes associated with significant methane. Methane can be trapped as free gas in permafrost for a long time. Gas ‘kicks’ have been observed in relatively shallow boreholes in the Yamal Peninsula in the past, and these are not an unusual occurrence in such settings. Furthermore, thawing permafrost makes carbon bioavailable to microbes that can then produce methane.

So finding methane in these settings is not too big a surprise.

She said rocks may have been ejected upward when methane-containing natural gas – stored in the permafrost but kept under pressure by the weight of the pingos – suddenly released in the warmer temperatures as the pingos collapsed and made the craters. That’s a less dramatic scenario than the original idea, which was that methane in and of itself exploded upward forcefully enough to create the giant holes.

Andrei Plekhanov, senior researcher at the Scientific Research Centre of the Arctic, stands at the first large crater, discovered recently in the Yamalo-Nenets Autonomous Okrug region of northern Russia.  Image via China Post.

Andrei Plekhanov, senior researcher at the Scientific Research Centre of the Arctic, led the team that investigated the first large crater, B1, discovered in July 2014 in the Yamalo-Nenets Autonomous Okrug region of northern Russia. Image via China Post.

Helicopters found the first crater.  Reindeer herders report a second.  Photo of first crater via Siberian Times.

Helicopters found the first crater. Reindeer herders reported a second. Photo of first crater, B1, via Siberian Times.

Last summer, when the first crater was found, the University of Stockholm had just reported what it called “vast methane plumes” escaping from the floor of the Arctic Ocean. They were found by scientists aboard the icebreaker Oden, which was in the Arctic exploring and measuring methane release from the seafloor.

Read more: Scientists discover vast methane plumes escaping from Arctic seafloor

Methane, as you may know, is a powerful greenhouse gas, more powerful than carbon dioxide. It has the potential to accelerate global warming rapidly via a feedback loop. In other words, scientists have said, as climate warms, methane is being released into the atmosphere both from permafrost and from the Arctic seafloor. This expelled methane increases temperatures more rapidly than carbon dioxide would by itself. The warmer temperatures cause more methane to be released and thus more warming; hence, the feedback loop.

That potential has not gone away. But, in the midst of thinking about that possibility, the news that giant holes in Siberian permafrost are not being blasted out by an explosive methane release is comforting.

The walls of the crater appear evenly cut.

Here is the first crater, B1, again. When scientists first examined it, its walls appeared evenly cut. There was water, from melting permafrost, cascading down the crater walls. Photo by Andrey-Naumenko via Siberian Times.

The crater, which is 70 meters deep, has an icy lake at its bottom.  Photo by Andrey-Naumenko via Siberian Times.

On examination, B1 appeared to be about 70 meters deep. It was reported to have an icy lake at its bottom. Photo by Andrey-Naumenko via Siberian Times.

Bottom line: Siberian Times reported a total of seven mystery craters in Siberia in February 2015, with one scientist speculating on the possibility of “20-30 more.” Meanwhile, other scientists are suggesting that the craters are formed not by explosive methane release, as was previously suggested, but by another, less dramatic mechanism, the rapid melting of ice plugs known as pingos, due to unseasonably warm temperatures in Siberia over the past year.

Deborah Byrd

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