The Batagaika crater is the largest known retrogressive thaw slump on Earth, a massive gash in the permafrost of northern Yakutia, Russia, that has been expanding for decades as warming temperatures melt ancient frozen ground. Stretching over a kilometer long and reaching depths around 70 meters, it exposes layers of permafrost that have been frozen for hundreds of thousands of years. Local Yakutian people call it the “gateway to the underworld,” and scientists treat it as something nearly as dramatic: a window into more than half a million years of climate history that is collapsing in real time.
How the Crater Formed
Despite being widely called a “crater,” the Batagaika feature was not created by an impact or an explosion. It is a retrogressive thaw slump, a type of landform that develops when ice-rich permafrost begins to thaw and the ground above it collapses. The process at Batagaika unfolded over several decades in three distinct stages: first came gullying, then thaw slumping, and finally what researchers call “megaslumping,” when the feature grew beyond 20 hectares and took on its current enormous proportions.1Permafrost and Periglacial Processes. Batagay megaslump: A review of the permafrost deposits, Quaternary environmental history, and recent development
The triggering event was surprisingly mundane. Sometime between the 1940s and 1960s, the taiga forest covering the hillslope was disturbed, likely by logging or land clearing. Trees in permafrost regions do more than just provide shade; their canopy and root systems insulate the frozen ground underneath. Once the vegetation was stripped away, the exposed soil absorbed more heat from sunlight, and a gully began forming by the early 1960s.2Permafrost and Periglacial Processes. Batagay megaslump: A review of the permafrost deposits, Quaternary environmental history, and recent development By the 1980s, that gully had triggered active thaw slumping along its central section. Through the 1990s, the slump ballooned past the 20-hectare threshold into megaslump territory. By 2019, it covered roughly 80 hectares, with a headwall towering up to about 55 meters above the slump floor.3Permafrost and Periglacial Processes. Batagay megaslump: A review of the permafrost deposits, Quaternary environmental history, and recent development
The main processes driving the slump’s ongoing growth are headwall ablation, where the exposed frozen face melts and sheds material, and thermal erosion, where meltwater carves channels into the remaining permafrost. Together, these processes create what researchers describe as a distinctive terrain of icy badlands on the slump floor: a chaotic, hummocky landscape of mud, meltwater, and debris.4Permafrost and Periglacial Processes. Batagay megaslump: A review of the permafrost deposits, Quaternary environmental history, and recent development
Size, Shape, and the Speed of Expansion
Satellite imagery has allowed researchers to track the crater’s growth with striking precision. In August 1991, the slump covered about 0.19 square kilometers. By June 2018, it had reached 0.78 square kilometers, roughly tripling in area over 27 years.5Environmental Earth Sciences. Multisensory satellite observations of the expansion of the Batagaika crater and succession of vegetation in its interior from 1991 to 2018 That average expansion rate works out to about 0.026 square kilometers per year, but the rate has not been steady. Between 1991 and 1999, the slump grew at roughly 0.016 square kilometers per year. The pace more than doubled between 2010 and 2014, reaching about 0.039 square kilometers per year, a period that saw a 22.7 percent increase in total area.6Environmental Earth Sciences. Multisensory satellite observations of the expansion of the Batagaika crater and succession of vegetation in its interior from 1991 to 2018
As of measurements taken in October 2011, the slump had a maximum length of about 2,100 meters, a width of roughly 980 meters, and a maximum depth of about 70 meters. The depth is not uniform; it decreases toward the northeastern tail of the feature, giving the crater more of an elongated, tapering shape than a simple bowl.7Environmental Earth Sciences. Multisensory satellite observations of the expansion of the Batagaika crater and succession of vegetation in its interior from 1991 to 2018 It has continued expanding since those measurements, and satellite studies have documented vegetation gradually establishing itself on the older, more stable parts of the slump floor, even as the headwall keeps retreating at the margins.
Why the Walls Are So Tall and Unstable
The sheer scale of the Batagaika headwall comes down to what is frozen inside it. The permafrost exposed across the headwall is not just frozen dirt; it is ice-rich to an extraordinary degree. Volumetric ground-ice content in some of the exposed layers reaches up to 87 percent, meaning those horizons are more ice than sediment by volume.8Geomorphology. Landforms and degradation pattern of the Batagay thaw slump, Northeastern Siberia When that ice melts, the volume it occupied simply vanishes. The remaining soil cannot support itself, and the headwall collapses backward in a self-reinforcing cycle.
The relationship between headwall shape and slump floor is largely controlled by the cryolithological structure of these permafrost horizons, essentially the stacking of frozen layers with different ice contents and sediment compositions.9Geomorphology. Landforms and degradation pattern of the Batagay thaw slump, Northeastern Siberia Some layers are dense with massive ice wedges; others are more sediment-rich and erode differently. This layered structure is also what makes the headwall such a valuable scientific target, because different layers correspond to different periods of Earth’s climate history.
A 650,000-Year Climate Archive
The scientific excitement around Batagaika is not just about the spectacle of collapsing permafrost. The slump has carved through a sequence of Ice Age deposits that record climate variability stretching back 650,000 years or more. These layers capture the interaction of wind-blown sediment, slope processes, and freezing and thawing cycles on a hillslope that was episodically forested during warmer interglacial periods and barren during glacial ones.10Permafrost and Periglacial Processes. Batagay megaslump: A review of the permafrost deposits, Quaternary environmental history, and recent development Very few locations on Earth provide such a long, continuous record of terrestrial conditions in the deep Arctic.
Researchers analyzing molecular biomarkers preserved in the headwall have found clear differences in how organic matter was preserved between glacial and interglacial periods.11The Cryosphere. Molecular biomarkers in Batagay megaslump permafrost deposits reveal clear differences in organic matter preservation between glacial and interglacial periods During colder glacial periods, organic material tended to be preserved differently than during the warmer intervals when forests returned to the hillslope. These chemical fingerprints give scientists a way to reconstruct not just temperature swings but also what the local vegetation and soil ecosystems looked like at specific points in the past. In a region where ice cores and ocean sediment records dominate the paleoclimate conversation, having a terrestrial site with this kind of depth and resolution is unusually valuable.
Fossil remains have also been recovered from the slump and surrounding area, including bones and other material from Pleistocene megafauna. The combination of biological, chemical, and sedimentological evidence from a single exposed face makes Batagaika something of a one-stop archive for researchers interested in how Arctic landscapes responded to past episodes of warming and cooling.
Carbon on the Move
One of the more pressing questions about Batagaika concerns what happens to the organic carbon locked inside the permafrost once the headwall melts and the sediment is exposed to air and water. Permafrost globally stores enormous quantities of carbon, and when it thaws, microbes can begin breaking that carbon down and releasing it as carbon dioxide or methane. For a feature the size of Batagaika, the quantities are substantial: researchers estimated that roughly 12,000 tons of organic carbon are mobilized annually downslope of the headwall.12Permafrost and Periglacial Processes. A Third of Organic Carbon Is Mineral Bound in Permafrost Sediments Exposed by the World’s Largest Thaw Slump, Batagay, Siberia
The picture is more complicated than “thaw equals emissions,” though. Analysis of the exposed sediments found that about a third of the organic carbon pool interacts with mineral surfaces or metal elements in the soil. Specifically, up to 34 percent of the organic carbon is bound to minerals through complexation with metals or association with poorly crystalline iron oxides.13Permafrost and Periglacial Processes. A Third of Organic Carbon Is Mineral Bound in Permafrost Sediments Exposed by the World’s Largest Thaw Slump, Batagay, Siberia That mineral-bound carbon is not readily available for microbes to break down, meaning it could remain locked in the soil and sediment for much longer than the unbound fraction, at least as long as the local chemical conditions stay stable.
This is a meaningful finding for climate projections. If every ton of carbon released from thawing permafrost went straight into the atmosphere, the climate feedback from sites like Batagaika would be severe. But with roughly a third of the carbon effectively shielded by mineral interactions, the actual atmospheric contribution is likely lower and slower than a worst-case scenario would suggest. That said, the other two-thirds of the carbon pool is more vulnerable, and 12,000 tons a year from a single site is not trivial. Multiply that kind of release across the thousands of smaller thaw slumps forming throughout Siberia and the Arctic, and the cumulative effect adds up.
How Researchers Collect Samples From the Headwall
Studying Batagaika in person is not easy. The site sits in the remote Yana Uplands of northern Yakutia, far from paved roads and accessible infrastructure. The headwall itself is a near-vertical cliff of melting permafrost that actively sheds material. To collect samples from the exposed layers, researchers have to rappel down the face of the headwall on ropes, using a hole saw mounted on a handheld power drill to extract small horizontal cores of frozen sediment from specific horizons in the exposed face.14The Cryosphere. Molecular biomarkers in Batagay megaslump permafrost deposits reveal clear differences in organic matter preservation between glacial and interglacial periods Each core was about 57 millimeters in diameter and 40 millimeters deep, small enough to transport but large enough to contain the biomarkers and sediment characteristics researchers needed.
The fieldwork is time-sensitive, too. During the brief Arctic summer, the headwall surface thaws and becomes unstable. Sampling has to happen when conditions allow access but before the exposed layers degrade beyond usefulness. Much of the broader monitoring work relies on satellite imagery and remote sensing, which is how the multi-decade expansion record has been assembled. But for chemical analysis, isotopic dating, and biomarker work, there is no substitute for physically drilling into the frozen face.
Why Locals Call It the Gateway to the Underworld
The Yakutian people living near Batagaika have watched the feature expand dramatically within living memory, and they have not been enthusiastic about it. The local name for the crater translates roughly to “the doorway to the underworld.”15Quaternary Research. Gateway to the underworld crater is helping scientists map the Earth’s climate history The name reflects genuine unease: the slump produces loud booming and cracking sounds as ice collapses and chunks of the headwall calve off. The feature has swallowed parts of a road and altered local drainage patterns, making it more than an abstract scientific curiosity for nearby communities.
In Yakutian culture, the underground is associated with spirits and other forces, and a gaping wound in the earth that grows larger every year fits naturally into that framework. The nickname has stuck in international media coverage and has probably done more to raise awareness of permafrost degradation than any number of academic papers. There is a useful irony in that: a feature named for superstition has become one of the most important field sites for understanding the entirely real and measurable consequences of Arctic warming.
Batagaika in the Context of Arctic Permafrost Loss
Batagaika is the biggest, but it is far from the only retrogressive thaw slump in the Arctic. Thousands of similar features have been identified across Siberia, northern Canada, and Alaska, and their numbers are increasing as temperatures rise. What sets Batagaika apart, beyond its size, is the depth of the permafrost record it exposes and the sheer volume of ground ice involved. Most thaw slumps cut through a few meters of ice-rich material before stabilizing. Batagaika’s headwall rises 55 meters and shows no sign of stabilizing, because the permafrost beneath it remains deeply ice-rich through multiple geological horizons.
The trajectory of the slump’s growth tracks what climate scientists would expect from rising Arctic temperatures. The fastest period of expansion, between 2010 and 2014, corresponded to a stretch of unusually warm summers in northeastern Siberia. Permafrost thaw is not a linear process; it tends to accelerate once a threshold is crossed, because the newly exposed dark soil absorbs more heat than the reflective snow and vegetation it replaces. This positive feedback loop is visible at Batagaika, where the rate of expansion more than doubled compared to the 1990s.16Environmental Earth Sciences. Multisensory satellite observations of the expansion of the Batagaika crater and succession of vegetation in its interior from 1991 to 2018
The feature also complicates one of the more hopeful narratives about permafrost carbon. Some models assume that vegetation will quickly recolonize thawed permafrost terrain, helping to stabilize the soil and recapture some of the released carbon. At Batagaika, vegetation has indeed started to grow on the older, more stable parts of the slump floor. But the headwall keeps retreating faster than plants can establish on the freshly exposed material, so the net effect is still one of ongoing carbon mobilization rather than recovery. Whether that balance eventually tips toward stabilization will depend on how much further the slump can expand before it runs out of sufficiently ice-rich permafrost to sustain its own growth.
The Soils Around the Crater
The landscape surrounding Batagaika is underlain by typical cryogenic soils of the Siberian larch forest zone. These soils tend to be acidic and waterlogged near the permafrost table, with a noticeable dip in pH levels close to the frozen layer. The larch forests growing on these soils are sparse and slow-growing, which is part of why the vegetation disturbance in the mid-twentieth century was so consequential. In a warmer climate with faster-growing forests, the canopy might have recovered before permafrost thaw accelerated. In Yakutia’s extreme continental climate, where winter temperatures regularly drop below minus 40 degrees Celsius and the growing season is brutally short, recovery takes decades. The forest that was cleared 60 or 70 years ago has not grown back over the slump, and the disturbed ground that initiated the whole process is now a chasm deep enough to swallow a 20-story building.
Around the crater’s edges, the intact larch forest continues to provide some insulation to the underlying permafrost, but researchers have noted signs of degradation in the transition zone between forest and slump. Cracks, small sinkholes, and areas of leaning “drunken trees,” where root systems have been destabilized by shifting ground, suggest that the slump’s influence extends beyond its visible boundaries. Whether these edge effects will eventually trigger new areas of collapse or simply stabilize remains one of the open questions about the site’s future.