Deep, cylindrical craters in the permafrost of Siberia have puzzled researchers since they were discovered a decade ago. Researchers now propose that the distinctive structures are caused by a build-up of hot gas beneath the permafrost. Warming Arctic temperatures might then weaken the permafrost so much that the gas explodes through its surface.
鈥淐limate change is likely the triggering factor, but it happens there because you have the thinning of the permafrost due to the gas,鈥� says at the University of Oslo in Norway.
As permafrost continues to thaw, more of the explosive craters could form, posing a threat to the extensive oil and gas infrastructure in the region, as well as representing an uncounted source of planet-warming methane emissions.聽Exploding craters could both release gas trapped beneath the permafrost and generated within it.聽鈥淲e are going to see more of these, and other kinds of release of gas,鈥� says at the University of Hawai驶i.
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The first of these craters 鈥� now called 鈥済as emission craters鈥� 鈥� was discovered in 2012 in Russia鈥檚 Yamal peninsula. At least seven others have since been identified in the region, although many more might have formed and then frozen over. Some of the craters are more than 50 metres deep and more than 20 metres wide. 鈥淭hese features are really quite spectacular,鈥� says Hellevang. 鈥淎lmost completely circular, and big and deep.鈥�
Researchers have put forward a number of different explanations for the craters. For instance, some propose the craters formed when thawed areas within the permafrost expanded, and filled with methane and other gases also generated from within the permafrost.
But Hellevang and his colleagues argue such scenarios fail to explain why the craters only appear to form in one particular region of the Arctic. He also says processes within the permafrost couldn鈥檛 generate the amount of gas required to produce such violent explosions; some of the craters are ringed by bus-sized chunks of ice thrown hundreds of metres away from the hole.
Instead, in a study that has yet to be peer-reviewed, the researchers propose the craters are due to hot, methane-rich natural gas welling up from a deeper source, such as a geological fault in the sediment below the permafrost. In their model, the heat from the gas then thaws the permafrost from below, while warming atmospheric temperatures weakens it on the surface, eventually triggering an explosion.
鈥淚 think their idea makes sense,鈥� says Schurmeir, who , but with a different source of gas. However, she says the researchers lack observations from an actual crater to back up the process they describe, and that more than one process could be behind the craters.
But if the new model is right, it might suggest the craters are more than just a geological curiosity. An increase in such craters due to climate change would not only pose a danger to railways and oil and gas pipelines in the region, but the trapped methane they released would be an uncounted source of methane emissions.
鈥淚t might be Siberia showing us how these things fail,鈥� says at the University Centre in Svalbard, Norway, who recently are probably trapped beneath the permafrost in Svalbard, which is geologically similar to the Yamal peninsula. 鈥淚f that鈥檚 the standard way that large accumulations fail then you鈥檙e dumping a lot of methane in a very short time.鈥�
EarthArxiv
