In the middle of last summer came news of a bizarre occurrence no one could explain. Seemingly out of nowhere, a massive crater appeared in one of the planet's most inhospitable lands. Early estimates said the crater, nestled in a land called "the ends of the Earth" where temperatures can sink far below zero, yawned nearly 30 metres in diameter.
One of the craters in Siberia's so-called "ends of the earth"
[5]
[6]
[7]
The saga deepened. The Siberian crater wasn't alone. There were two more, ratcheting up the tension in a drama that hit its climax as a probable explanation surfaced. Climate change had thawed the permafrost, which had caused methane trapped inside the icy ground to explode. "Gas pressure increased until it was high enough to push away the overlaying layers in a powerful injection, forming the crater," one German scientist said at the time.
Video of the craters...
* * *
Now, however, as The Sydney Morning herald reports, [8] researchers fear there are more craters than anyone knew — and the repercussions could be huge...
Russian scientists have now spotted a total of seven craters, five of which are in the Yamal Peninsula. Two of those holes have since turned into lakes. And one giant crater is rimmed by a ring of at least 20 mini-craters, the Siberian Times reported. Dozens more Siberian craters are likely still out there, said Moscow scientist Vasily Bogoyavlensky of the Oil and Gas Research Institute, calling for an "urgent" investigation.
He fears that if temperatures continue to rise — and they were five degrees higher than average in 2012 and 2013 — more craters will emerge in an area awash in gas fields vital to the national economy. "It is important not to scare people, but to understand that it is a very serious problem and we must research this," he told the Siberian Times. "We must research this phenomenon urgently, to prevent possible disasters."
...
These objects need to be studied, but it is rather dangerous for the researchers," Bogoyavlensky told the Siberian Times. "We know that there can occur a series of gas emissions over an extended period of time, but we do not know exactly when they might happen. ... It is very risky, because no one can guarantee there would not be new emissions."
Making matters worse, the gas is extremely flammable. One of the methane bursts has already caught fire. Nearby residents in a town called Antipayuta say they recently saw a bright flash in the distance. "Probably the gas ignited," Bogoyavlensky said. "This shows us that such [an] explosion could be rather dangerous and destructive. Years of experience has shown that gas emissions can cause serious damage to drilling rigs, oil and gas fields and offshore pipelines."
When the news first broke last year, social media users pointed to everything from a meteorite to a stray missile to aliens to the Bermuda Triangle as possible causes. But the most plausible explanation seemed to be the explosive release of melting methane hydrate—an ice-like material frozen in the Arctic ground—thanks to global warming. But, as National Geographic reports, other theories are coming to light...
Now, scientists are arguing that the methane theory is unlikely, based on new satellite surveys released by Russian researchers that found dozens of new craters in Siberia.
"The jury is still out" on the cause of Siberia's craters, says Carolyn Ruppel, chief of the U.S. Geological Survey's Gas Hydrates Project. But she and other scientists say the new satellite mapping suggests another explanation that has to do with the rapid melting of ice cores called pingos.
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. But that process alone isn't enough to explain the ejected rocks that have been found around the rim of the craters, which suggest some sort of explosion.
Instead, Ruppel theorizes that the craters were formed by a sudden release of natural gas that had been stored in the permafrost but was kept under pressure by the weight of the pingo.
This theory is bolstered by the Russian satellite data, which show pingos—they appear as small mounds—in the exact positions where the craters later formed.
* * *
So in conclusion - "No one knows what is happening in these craters at the moment."