There is a place in Siberia known as Yamal, which literally translates as "the end of the world."

It is an area that is notorious for earth-shattering events, as this was the region where the most dangerous meteor in recent history struck in 1908 with devastating results. Thankfully, the blast occurred in a relatively uninhabited zone, but forests were levelled over a distance of 2000 square kilometers (1242 miles).

Yamal is now the site of another unlikely happening in the form of a huge, unexplained crater, estimated by observers to be around 50 meters (164 feet) wide and 70 meters (229 feet) deep with water from melting permafrost cascading down its sides into snow-covered depths.

The crater was spotted by passengers in a Russian oil-and-gas industry helicopter who were flying over a forest some 30 kilometres from Yamal’s biggest gas field Bovanenkovo. The surprised passengers filmed the hole and one of them, engineer Konstantin Nikolaev, uploaded the footage to YouTube generated a flurry of interest worldwide.

Theories to explain the mysterious cavity are now rife, and these range from further meteor strikes, weapon-testing and the effects of global warming to more unusual explanations such as UFO impact and secret entrances to "hollow Earth" underground societies.
The Russian authorities are baffled and have yet to provide an explanation for the hole’s appearance:

“We can definitely say that it is not a meteorite,” a spokesman for Russia’s Emergencies Ministry has told media.

Russian scientist Anna Kurchatova, from the Sub-Arctic Scientific Research Centre, favors global warming as a likely explanation, due to the geological conditions of the area. She explained that Siberia’s frozen soil — known as permafrost — is filled with millions of tons of methane gas. When surface temperatures increase, the gas begins to be released, pooling into highly volatile pockets. These gas-filled chambers are very explosive, and Kurchatova thinks that one may have been ignited by mixture of water, salt and gas, or that the pressure of the gas building up underground simply caused a chamber to pop like a champagne cork.

The Yamal Peninsula in the Yamalo-Nenets Autonomous Okrug is Russia’s main production area for gas, and the Bovanenkovo field is of central importance to gas supplies from Siberia to the world. If exploding methane is the cause of the crater, there are concerns that this could be very dangerous, igniting other forms of gas in the area.

An investigative team, including experts from Russia’s Centre for the Study of the Arctic, and the Cryosphere Institute of the Academy of Sciences, have visited the hole to sample the soil, water and air at the scene, but they have still not been able to offer a specific explanation.

Though its cause remains unknown, the researchers maintain that there is was "nothing mysterious" about the phenomenon. "It is simply Mother Nature’s law with its internal pressure and changes in temperatures," researcher Andrey Plekhanov told the Siberian Times.
Despite the scientists’ reassurances, two further holes have now appeared, though the investigation team have not yet had the opportunity to visit the new sites. The latest craters are said to be smaller than the first, though in every other way "exactly" like their predecessor. One of the holes appeared in Siberia’s Yamal Peninsula in the Taz district and is reported to have a diameter of 49ft (15 metres), and the third was spotted on the Taymyr Peninsula in Kransoyark region and is said to have a diameter of 13ft (four metres).

The two latest holes were discovered by reindeer herders, who almost disappeared into the icy depths.

The Siberian holes are not the only inexplicable craters to have appeared across the planet in recent years: read about the other holes that have also appeared in Russia, and the inexplicable sink holes have closed Mount Baldy in America