The mystery of what caused that gigantic crater in the Yamal Peninsula of Siberia may have been solved. And the reason is scarier than all those totally valid theories involving aliens and meteorites.

Andrei Plekhanov, an archaeologist at the Scientific Centre of Arctic Studies in Salekhard, Russia, visited the massive cavity after it was discovered by reindeer herders in mid-July.

Plekhanov believes the roughly 100-foot wide hole, which was found in a region of northern Siberia so remote it is called “the end of the world,” was caused by an explosion of methane gas, which is normally trapped in the permafrost.

But here's the really scary bit.

Plekhanov reckons unusually hot summers in 2012 and 2013 caused the icy ground to thaw and collapse, releasing the trapped methane. Tests carried out by Plekhanov and his team showed unusually high concentrations of methane in the crater — 9.6 percent compared with normal methane concentration of air of 0.000179 percent. Yikes!

Plekhanov’s theory is supported by other scientists, including Hans-Wolfgang Hubberten, a geochemist at Alfred Wegener Institute in Potsdam, Germany.

Hubberten believes that gas pressure beneath the permafrost gradually increased before exploding through the surface like a popping champagne cork.

“Gas pressure increased until it was high enough to push away the overlying layers in a powerful injection, forming the crater,” Hubberten explained.

Some experts have described the crater as a "sinkhole," which are caused when the surface layer of soil collapses. Only this sinkhole pushed material out, rather than sucked it in like those opening up around the United States.

Check out this National Geographic interview with Randall Orndorff of the US Geological Society about why sinkholes open up.

The worry is that more of these giant craters could appear in the region, which happens to hold some of Russia’s largest gas and oil reserves, posing a threat to residents and workers, not to mention reindeer herders.

Already another two smaller craters have been found nearby, one measuring about 50 feet in diameter and the other 15 feet. Double yikes!

But Russian permafrost expert Marina Leibman doesn't believe global warming will necessarily lead to an explosion — pardon the pun — of craters in the region in the near future. That's because the temperature of the permafrost is so damn cold that slightly higher air temperatures won't have much of an impact. Yet.

“You can’t say in 20 years it will be 2 degrees (Celsius, 35.6 degrees Fahrenheit) warmer so permafrost will be thawing. It will make it 2 degrees warmer, but not thawing — at least in the far north," Leibman, chief scientist at the Earth Cryosphere Institute of the Siberian Branch of the Russian Academy of Sciences, told the New York Times.

“In the south, where you have only patches of permafrost, the response may be a little bit more active.

“But what we see now is permafrost with minus 1 degree temperature now — after a climate warming of 1 and a half degrees — permafrost temperature is minus 0.1 degree, but not above zero.”

Now, we're no scientist but 0.1 degree doesn't sound like much to us.

Fortunately, the local government is taking the matter seriously and is planning to carry out an in-depth study into the cause of the craters.

They may not like the answers.