(VIDEO 34 sec.) Scientists were concerned when, in July, 2014, a large hole mysteriously appeared on the Yamal Peninsula in Siberia, Russia.

Scientists are still searching for the cause of Siberia’s giant craters.

A news article dated July 27, 2014, in the China Post, identified the above 34-second video as the video which brought the crater to world attention, having been viewed more than seven million times [as of 2015, more than 10 million times]. The China Post quoted the videographer, a helicopter pilot (according to Nature World News [link below]), “named only as Bulka,” as stating:

“The crater is enormous in size — you could fly down into it in several Mi-8s (helicopters) without being afraid of hitting anything.”

With the Russian Mi-8 helicopter being 18.17 m (59 ft 7 in) in length, and the hole’s inside diameter being eventually measured at 30 m (about 98 feet/33 yards) in approximate diameter, Bulka’s observation may be an accurate, if unsafe, visualization.

Nature.com provided a summary of the speculation on potential causes of the crater:

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 5̊C. 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 2̊C, 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.

By July 30, 2014, two more craters had been discovered, the creation of one having been partially witnessed in 2013. Click next page for that story.