This massive hole, which spans about 260 feet in diameter, was recently discovered by pilots flying over a remote area of Siberia known ominously as "the end of the world." Nobody yet knows how or why it formed, but a team of scientists have been flown in to investigate, reports USA Today.

The strangely shaped orifice looks unnatural, and ever since now unavailable video of the odd feature was distributed online, the Internet has been abuzz with wild conspiracy theories: Invading extraterrestrials? Secret weapons tests gone wrong? An entrance into the underworld? Giant mutant worms? An interdimensional stargate?

A meteorite strike has apparently been ruled out as the culprit.

More sensible theories have also been postulated, of course. The most likely scenario involves some kind of explosion caused by a mixture of gas, salt and water igniting underground. This theory is strengthened due to the hole's proximity to a natural gas field; the region is teeming with combustible materials. Debris around the hole also represents signs of combustion.

Dr. Chris Fogwill, a polar scientist at the University of New South Wales in Australia, has suggested the hole might be what's left of a "pingo," a heap of Earth-covered ice commonly found in Arctic regions. An extremely large, melting pingo could have left such a cavern.

"Certainly from the images I've seen it looks like a periglacial feature, perhaps a collapsed pingo," Fogwill told The Sydney Morning Herald. "This is obviously a very extreme version of that, and if there’s been any interaction with the gas in the area, that is a question that could only be answered by going there."

Interestingly, both of these explanations hint at a deeper cause: global warming. The explosive mixture of gas, salt and water could have been released and ignited due to a warming local climate. Likewise, rising temperatures would certainly explain a melted pingo.

New footage of the giant hole, released as scientists arrived on the scene, can be viewed below, but the audio is all in Russian:

So far a clear explanation for the hole is still forthcoming, but scientists are said to be collecting samples of soil, air and water from the area. The depth of the hole has not yet been determined either, but these new images do show that the bottom is saturated with a murky fluid.

Because the hole is in such a remote region, it's also possible it formed some time ago and was only recently discovered. The region is famous for many other bizarre discoveries as well, such as ancient viruses released by the melting permafrost, and frozen remains of wooly mammoths.

Bryan Nelson ( @@brynelson ) writes about everything from environmental problems here on Earth to big questions in space.

Giant hole mysteriously forms in Siberia, and nobody knows why
The gaping 260-foot-wide hole was spotted in an area of Siberia known as "the end of the world."