By Katia Moskvitch
31 July 2014
(Nature) – A mystery crater spotted in the frozen Yamal peninsula in Siberia earlier this month was probably caused by methane released as permafrost thawed, researchers in Russia say.
Air near the bottom of the crater contained unusually high concentrations of methane — up to 9.6% — in tests conducted at the site on 16 July, says Andrei Plekhanov, an archaeologist at the Scientific Centre of Arctic Studies in Salekhard, Russia. Plekhanov, who led an expedition to the crater, says that air normally contains just 0.000179% methane.
Since the hole was spotted in mid-July by a helicopter pilot, conjecture has abounded about how the 30-metre-wide crater was formed — a gas or missile explosion, a meteorite impact and alien involvement have all been suggested.
But Plekhanov and his team believe that it is linked to the abnormally hot Yamal summers of 2012 and 2013, which were warmer than usual by an average of about 5°C. As temperatures rose, the researchers suggest, permafrost thawed and collapsed, releasing methane that had been trapped in the icy ground.
Other researchers argue that long-term global warming might be to blame — and that a slow and steady thaw in the region could have been enough to free a burst of methane and create such a big crater. Over the past 20 years, permafrost at a depth of 20 metres has warmed by about 2°C, driven by rising air temperatures1, notes Hans-Wolfgang Hubberten, a geochemist at the Alfred Wegener Institute in Potsdam, Germany.
Hubberten speculates that a thick layer of ice on top of the soil at the Yamal crater site trapped methane released by thawing permafrost. “Gas pressure increased until it was high enough to push away the overlying layers in a powerful injection, forming the crater,” he says. Hubberten says that he has never before seen a crater similar to the Yamal crater in the Arctic. [more]