The exact cause of dozens of mysterious craters that are increasing in number and which are located in a place called "End of the World" in Siberia continues to baffle scientists.

Speculation has it the large holes could be sinkholes; meteorite craters; craters left by the explosions of underground natural gas pockets or craters caused by UFOs. The massive holes were first discovered by local residents of the frozen Yamal Peninsula in 2013.

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The Yamal Peninsula in the far north of Russia has an area of 700 kilometers and consists mostly of permafrost ground. The word Yamal in the language of the indigenous inhabitants, the Nenets, translates into "End of the World."

In 2013, however, a new crater appeared in the tundra and the Nenets reported hearing a loud explosion heard over 100 kilometers away and preceded by a glow in the sky. Since then, the crater's size has increased at least 15 times. Initially measuring about 4 meters across, it's grown to 70 meters today and has formed a lake.

The growth in the crater's depth is also remarkable. Its depth was estimated at 100 meters when it was discovered. Scientists have been unable to measure its current depth.

A Russian scientist, Dr. Vladimir Epifanov, has collected information about the dozens of new craters in the region in an effort to understand what caused them, and how they might evolve in the future.

Epivanof said although there isn't a definite explanation for the bright light in the sky in 2013 and the loud bang, he believes the craters were caused by an explosive mix of methane or other underground gases released when temperatures rise.

Other scientists agree most craters in the Siberian region might have been formed by "pingos," which are dome-shaped mounds over a core of ice that erupt under pressure from methane gas released by the thawing of permafrost.

Epivanof, however, is unsure if a pingo caused the massive 2013 crater, saying the explosion originated at such a depth it was unlikely rising temperatures had anything to do with it.

The Russian Emergencies Ministry earlier ruled out a meteorite as the crater's cause. Also improbable is the claim the crater was caused by a crashed UFO or Unidentified Flying Object.

Tagscraters, End of the World, Yamal Peninsula, Siberia