Physical explanation for the ‘holes at the end of the world’ in Siberia

September 27 () –

Scientists offer new perspective on the origins of craters sighted for the first time on the Yamal Peninsulain Siberia, in 2014, known as the ‘holes at the end of the world’.

These mysterious cylindrical holes in the permafrost, the always frozen ground, were caused by pressure changes driven by climate change that explosively released frozen methane underground, according to the new study.

Additionally, it has been discovered that the unusual geology of the region, together with climate warming, initiated a process that led to the release of methane gas from methane hydrates in the permafrost.

“There are very, very specific conditions that allow this phenomenon to occur.“said Ana Morgado, chemical engineer at the Cambridge University and one of the authors of the study. “We are talking about a very specific geological space.”

The research was published in Geophysical Research Letters.

The Yamal Peninsula is a low-lying landmass jutting into the Kara Sea from north-central Russia. In 2014, it was reported sudden appearance of a crater approximately 70 meters in diameter at its widest point in the permafrost. Over the following decade, other craters have been found on both the Yamal Peninsula and the nearby Gydan Peninsula.

Many explanations for the craters have emerged over the past 10 years, attributing the explosions to a buildup of methane gas underground due to melting permafrost, or to the craters’ proximity to natural gas reserves.

But the authors found that warming permafrost alone would not be enough to cause an explosion. The new explanation says that surface heating leads to a rapid change in pressure deep underground, which causes the release of explosive methane gas.

“We knew something was causing the methane hydrate layer to break down,” Morgado said. “It’s a bit like detective work.”

PHYSICS OR CHEMISTRY

The researchers solved the puzzle from the bottom up, first considering a basic question: Were the explosions caused by physical or chemical processes?

“There are only two ways for an explosion to occur.“says Julyan Cartwright, geophysicist at the Higher Council for Scientific Research (CSIC) and one of the authors of the study. “Either a chemical reaction occurs and an explosion occurs, as if it were dynamite, or the tire of the bike until it explodes; That’s physics.”

In this case, he says, there was no evidence that the explosions were caused by chemical reactions, so they must have had a physical source. “And then you have to think, What is the pump that inflates the bicycle tire?” he states.

The authors claim that the pump was osmosis, which is the way a fluid moves to equalize the concentration of substances dissolved in it. Salt water is a classic example. If a barrier exists that allows water to pass through, but not salt, pressure can build up on the salty side as water flows toward it.

The thick, clayey permafrost of the Yamal Peninsula acts as an osmotic barrier, and warming is changing it. This layer, between 180 and 300 meters thick, remains permanently frozen throughout the year. An “active layer” of topsoil above it thaws and refreezes seasonally.

Scattered throughout the tundra and encased within the permafrost are unusual meter-thick layers of unfrozen water and high salinity called cryopegs, which are kept liquid by a combination of pressure and salinity. Beneath the cryopegs is a layer of crystallized methane and water solids, called methane hydrates, which remain stable due to high pressure and low temperature.

But warmer temperatures are destabilizing these layers. Climate change has caused the active layer to melt and expand downward until it reaches the cryopeg, releasing water that travels through osmotic pressure toward the cryopeg, the researchers found.

But there is not enough room in the cryopeg to contain the additional meltwater forced by osmosis, so the pressure increases. The increasing pressure creates cracks in the soil that move upward from the cryopeg toward the surface. Then the pressure gradient reverses: the cracked soil causes a sudden drop in pressure at depth. That pressure change damages the methane hydrates beneath the cryopeg, causing a release of methane gas and a physical explosion.

The study found that the period leading up to the explosion can last decades. That timeline aligns with the increase in climate warming starting in the 1980s.

The new explanation depends on how climate warming and the region’s geology interact to create the explosions, which are unique to the Yamal Peninsula.

“This could be a phenomenon that occurs very infrequently,” Morgado said. “But the amount of methane that’s being released could have a pretty big impact on global warming.”