Massive "slumps" are forming like a pox across the Northern Hemisphere — deep craters that appear like gateways to the underworld — and they could represent an ominous sign of what's to come, reports The Independent.

The largest of these so-called megaslumps is Batagaika crater in Siberia, a kilometer-long crevasse that's 90 meters deep. The unusual chasm appears almost as if the land is turning itself inside out. Even more frightening, it's widening by up to 20 meters a year, slowly encroaching upon the landscape like a living thing.

The cause of these eerie sinkholes is melting permafrost — the frozen soil and rock that makes up the bulk of the Arctic landscape. As our planet continues to warm, the permafrost thaws and the Earth loosens and slumps. This process not only disfigures the terrain, but it also releases dangerous greenhouse gases into the air that had otherwise been trapped by the frozen ground's grip.

“As the climate warms – I think there’s no shadow of a doubt it will warm – we will get increasing thaw of the permafrost and... there will be more slumps and more gullying, more erosion of the land surface," explained Professor Julian Murton, a geologist at the University of Sussex who has recently visited Batagaika crater to study its features.

The release of greenhouse gases — most notably, methane — from melting permafrost is what is known as a climate feedback loop. As the planet warms, more permafrost melts and more greenhouse gases get released into the atmosphere, which leads to more warming and even more thawing, and so on. Once a process like this gets triggered, it becomes very difficult to stop. This is one reason that researchers warn that megaslumps like the Batagaika crater represent major threats to our planet's climate. They're an omen, a symptom, of a larger underlying disease.

Local people won't approach the cliffs that mark the edges of Batagaika crater, for fear that the hole will suddenly expand and suck them in. Their fears aren't entirely unwarranted. The cliffs are treacherous, and they are expanding. But even more treacherous is the landscape at the bottom of the crater, which Professor Murton compares to the Badlands of the southwest United States, full of ravines and gullies.

The land has so rapidly opened up that the decaying remains of long-dead mammoths, musk ox and horses can sometimes be seen. Ancient tree stumps protrude from the ground. It's understandable why some people have likened these fissures to gateways to the underworld.

“At the bottom of the slump is rock … I haven’t seen any gateway to hell,” said Murton, as if he had to visit the site firsthand before knowing for sure.

"This thing is growing remarkably quickly,” he added. “If you’ve got roads or paths nearby, they could easily get consumed as this thing grows… so it poses a hazard to the locals."