These days the biggest mysteries that people are talking about seem to be bright spots, woolly rhinos, Martian "blobs," and yes, even blue-and-black dresses... or is it gold and white?! However, last summer, the world was transfixed by massive holes that had mysteriously appeared in Siberia seemingly overnight. Now, upon the arrival of even more holes, experts have come up with a promising theory about their origins.

Missed all the Fuss? Here's a Recap:

The first gigantic crater was spotted last July when a helicopter was flying over northern Russian in the Yamal peninsula - a region appropriately named the "end of the world."

The hole, which was first seen in a video uploaded by one of the helicopter pilots, was estimated to be a whopping 250 feet wide and seemingly bottomless. It looked almost like a crater, but closer inspection showed that this was no impact. Stone and soil appeared to have been thrown upwards, not to the side, before settling in loose mounds around the hole's rim.

"We can definitely say that it is not a meteorite," Yamal's branch of the Emergencies Ministry told The Siberian Times, who first broke the story half-a-year ago.

Concerns were quickly shared that this was then caused by a gas explosion, especially because Yamal plays host to a massive natural gas field a mere 18 miles away from the crater. If explosions were occurring, potentially prompted by unforeseen chemical releases, the region could have been in big trouble, with field workers' lives at risk.

Thankfully, Andrey Plekhanov, Senior Researcher at the State Scientific Centre of Arctic Research, who was sent with a team to investigate the phenomenon, was able to quell those concerns and found no evidence of charring in the soil.

"I want to stress that it was not an explosion, but an ejection, so there was no heat released as it happened" he told The Siberian Times and other local media outlets. (Scroll to read on...)

Plekhanov and his team surveyed the crater, even descending into it to take geological measurements. They found a flowing lake of ice-water at the bottom of the hole, which was estimated to be up to 230 feet deep (70m).

Craters and Theories Abound

And that discovery backed one of the leading theories about the craters - two more of which were identified by the end of the July. As first proposed by experts at the University of South Wales, many now suspect that the craters are being formed by unusually large pingos.

A pingo often forms when a mass of ice embedded in the earth starts to get pushed towards the surface by free-flowing ground water just beneath it. This water is i turn rushing upwards to fill cracks in Yamal's permafrost, which has seen significant melt in recent years thanks to rising temperatures. In fact, 2014 was the hottest year on record, with even Siberia seeing some unusually hot days. (Scroll to read on...)

However, new satellite imagery of Yamal and its surrounding Arctic region has revealed at least four more massive craters in the last few months, one of which could be surrounded by as many as 20 mini-craters, according to the Moscow-based Oil and Gas Research Institute (AGRI), via The Siberian Times.

The mini-crater hole has even since become a massive lake surrounded by smaller ones, suggesting that the ice that formed it quickly melted. Because the pingo was resting on frozen and saturated soil, its meltwater had nowhere to go and simply pooled in the craters.

Still, causing so many massive pingos at once would take a lot of groundwater, potentially more than even the melting permafrost could supply. So what's going on?

As it turns out, the Earth might be passing gas.

Vasily Bogoyavlensky, deputy director of the AGRI with the Russian Academy of Sciences, is proposing that natural gas is to blame. No, he's not saying that these craters were caused by explosions, but he is suggesting that massive amounts of trapped gas could have erupted out of the ground at once, forcing their way through cracked permafrost even ahead of loose water and ice.

According to local media, an AGRI team has theorized that as Arctic permafrost continues to melt, pockets of hydrocarbons are being freed. These are not unlike the pockets of methane gas that are being periodically released from the Arctic seafloor, after a great deal of Siberia's coastline was submerged during the glacial maxim 20,000 years ago. (Scroll to read on...)

This freed gas may be rushing to the weakest points in a thin ceiling of surface permafrost. There, it is building in pressure, with groundwater and potential pingo formation pushing from below.

Trapped between ice and a cold place, the gas eventually pushes out with incredible force, sending earth flying even as rushing water sends the pingo plowing through the gas breach. And while this alone is not particularly deadly, as it's unlikely to ignite, officials in the area are still concerned about the nearby Yamal gas fields.

"Years of experience has shown that gas emissions can cause serious damage to drilling rigs, oil and gas fields and offshore pipelines," Bogoyavlensky said. "It is important not to scare people, but to understand that it is a very serious problem and we must research this."

Vladimir Romanovsky, a geophysicist who studies permafrost at the University of Alaska Fairbanks, added in an interview with New Scientist that we're just noticing these craters now because it's becoming more common - numbers noticeable even in the Sleeping Lands. Some have theorized there may be 10 times as many craters out there than have been found.

"If the warming continues," he said, "we will see more and more of this phenomenon."

The geologist added that we could even potentially see it occur in other Arctic regions of the world, like parts of Alaska and Canada.

Still, not everyone is convinced. Carolyn Ruppel, chief of the US Geological Survey's Gas Hydrates Project, recently told National Geographic that the gas pockets in question are normally a whopping 740 feet or more underground. That's about three times the depth of the deepest crater seen so far. If the AGRI theory is correct, then experts would still be stuck wondering what could be prompting melting that deep.

That then just adds mystery to the mystery that's occurring in the "End of the World."

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