On the remote Yamal and Gydan peninsulas of western Siberia, the landscape is marked by massive craters that look as though the Earth has blown holes in itself. While the origin story of these gas-emission craters (GECs) has remained somewhat of a mystery since the first one was discovered back in 2014, scientists now believe they know what's causing them.
These fascinating GECs – all rocky cylinders plunging as deep as 164 m (538 ft) and stretching up to 30 m (98 ft) in width – have steep walls lined with layers of permafrost. So far, only eight craters have been documented since 2014, but each one has stunned scientists and locals with its scale and geological drama. Now, University of Oslo researchers, along with colleagues in Russia, have argued that the power to create them comes not just from thawing permafrost on the surface, like Siberia's "Gateway to Hell" Batagaika crater, but as a result of methane and heat pushing up with force from deep below the ground.
In their study, the team reviewed every major hypothesis so far put forward to explain GEC formation. Some explanations suggested warming permafrost was to blame – including the growth of liquid salt water pockets called cryopegs, which can expand and create cavities or gas-filled chambers. Others proposed that the melting of gas-charged ground ice or the breakdown of methane hydrates – icy crystals of water and methane that are stable only under cold, high-pressure conditions – in the frozen ground was driving it. But what's puzzled scientists is that these kinds of craters have only appeared in western Siberia. If these near-surface-level processes were causing the explosions, they should have appeared throughout the Arctic.
In the new study, the scientists focused on physics. To test whether shallow cavities in frozen ground could really produce such violent blasts, as previoiusly suggested, the researchers built a simple model treating the surface layers of permafrost like a heavy cork in a pressurized bottle. They varied the thickness of this frozen "cork" and the size of the gas-filled chamber beneath it, and calculated how much pressure would be needed to hurl debris the distances it can be seen around the craters. What they found was that small, shallow cavities were incapable of delivering enough force before leaking gas and losing that explosive power.
As such, the power that drives these craters, according to the scientists, most likely comes from much larger underground cavities or deeper accumulations of methane pushing upward from beneath the permafrost.
The Yamal and Gydan peninsulas sit on vast gas reserves – with fault lines running through the rock below. The scientists argue that these fault lines allow for gas and heat to move up from below the permafrost. Where these fault lines intersect with lakes and rivers, the thick frozen ground is thinned by taliks, or areas of year-round unfrozen soil. These spots act as weak points, and when enough gas pressure builds from below, the frozen "cap" gives way suddenly, forming a near-vertical shaft that soon fills with water and ice. Within a few years, the crater resembles a thermokarst lake, which means there could be more craters essentially hiding in plain sight across western Sibera.
These findings also shift the role of climate warming in crater creation. Instead of directly producing explosions by melting shallow permafrost, a warming environment means lakes and thawed zones become more common and frozen ground along fault lines becomes weaker. But the real blast of energy comes from deeper methane and heat. And because methane is a greenhouse gas, each crater releases a concentrated amount of it into the atmosphere.
The scientists argue that this creates a feedback loop were gas releases add to global warming, which in turn speeds the spread of thawed zones and permafrost melt, setting the stage for more gas-fueled craters to form.
These findings significantly advance the modeling seen in 2024 research that pointed to thawing permafrost, salty cryopeg layers and methane hydrates as possible triggers. While those shallow processes can generate some amount of pressure, the team's latest research demonstrates that they aren’t powerful enough to explain the depth of craters and the debris that's been blasted hundreds of meters from the explosion site. The new work makes a solid case for deeper gas rising along fault lines as a key driver, with climate change acting more as an indirect influence rather than the main culprit.
"This leaves the models where natural gas generation and accumulation happen below the permafrost, and with local thinning and weakening of the overburden caused partly by climate change, the most likely," the researchers noted. "This resonates well with the vast natural gas accumulations in the region and is supported by geophysical surveys. This suggests that GECs can potentially also form elsewhere, but require connection to natural gas generation and accumulations below continuous permafrost."
The research was published in the journal Science of the Total Environment.
Source: University of Oslo via Phys.org
