Nearly a decade ago, a helicopter pilot flying over the remote expanses of Canada’s Northwest Territories noticed something profoundly peculiar on the landscape below: a landslide of such immense proportions that it had completely blocked a natural river and forged an entirely new lake in its wake. But while the sheer scale of the geological disruption was striking, it was not the damming power of the earth that caught the attention of researchers. What the pilot had witnessed was a phenomenon entirely unprecedented in the annals of modern science—an immense geological event that researchers have since classified as a "permafrost detachment slide."
In a recent scientific paper published in the academic literature, a dedicated team of geoscientists details two monumental occurrences of this phenomenon within the region. One of these staggering slides stretched for three-quarters of a mile, while the other measured a full two miles in length. Combined, these two catastrophic failures displaced an estimated 30 million cubic yards of earth, reshaping the remote northern topography in a matter of hours or days.
Unlike traditional landslides, which typically send a destructive, fast-moving torrent of rainwater, mud, and loosened rock tumbling down a mountainside, permafrost detachment slides operate under entirely different, highly complex physical mechanics. They occur when deeply frozen, ancient soils undergo severe thermal degradation, causing the structural integrity of the land to fail catastrophically from the inside out. Even more baffling to researchers, both of these massive slides trace their origins back three decades to historical wildfires, which slowly and imperceptibly altered the thermal balance of the underlying permafrost until the ground finally gave way entirely along the Johnson River in 2017 and the Redstone River in 2018.
When the research team traveled to the remote sites to conduct on-the-ground investigations, they discovered the terrain heavily embedded with massive chunks of frozen material, some measuring up to 650 feet long.
"It’s a very dramatic manifestation of the changing climate," said geoscientist Joseph Young, the lead author of the newly published paper, who conducted the extensive research while based at the University of Alberta. "They’ve only started happening in the last 10, 15 years, and it’s a very drastic and abrupt change in the landscape."
To understand the gravity of these findings, scientists point out that permafrost remains one of the major planetary wild cards in the global climate equation. Defined simply, permafrost is ground—ranging from soil and rock to sand and organic matter—that remains continuously frozen for two consecutive years or longer, frequently preserving ancient ice and dead plant material within its matrix. Across the vast expanses of the Northern Hemisphere, these permafrost zones cover an expansive territory roughly two and a half times the total size of the continental United States.
However, as the Arctic continues to warm at a staggering rate—measuring up to four times faster than the rest of the planet—the permafrost is now thawing at unprecedented speeds. This rapid degradation is gouging massive, unstable potholes across the northern landscape, a phenomenon known to geologists as thermokarst, which frequently releases massive, invisible clouds of potent greenhouse gases into the atmosphere as the trapped organic matter decomposes.
While thermokarst is a known and growing concern, the discovery of permafrost detachment slides demonstrates that single, isolated events can occur on a vastly larger, more devastating scale.
"I think it’s fascinating that we’re discovering a new type of thermokarst," said David Olefeldt, a soil scientist at the University of Alberta who studies permafrost dynamics and was not involved in the new research paper. "This is a type of land collapse due to permafrost thaw which hasn’t really been observed before."
The chain of events that culminated in these massive failures began decades prior, specifically in 1995, when a severe wildfire swept through the forested region. The intense flames burned away the dense canopy of vegetation that normally served as a protective thermal shield for the ground, keeping the underlying permafrost cool during the intense, long sunlight hours of northern summers. Stripped of this crucial insulation, the ground was left vulnerable.
"After about 20 years or so, that thermal signature from the burned forest can reach the base of permafrost," Young explained, outlining the long-term delayed reaction of the ecosystem. "It’s slight, but it’s there."
Crucially, the ultimate collapse of the permafrost did not happen because the surface simply melted into mud under the summer sun. Instead, the failure progressed from the bottom up through the complex matrix of soil, ice, and organic material. As the base of the permafrost warmed—even by a fractional amount—tension cracks began to propagate deep beneath the surface. This structural fracturing created pools of relatively warm water at the surface, which subsequently infiltrated deeper into the frozen ground, accelerating the internal decay.
As the frozen melange degraded, it initially began to slip downhill at a modest rate of a handful of feet per year. Over time, that movement accelerated to roughly 80 feet annually, before the entire mountainside suddenly gave way in a catastrophic detachment slide.
"This kind of movement can create its own release of energy because of friction and cracking on the bottom," noted Vladimir E. Romanovsky, a permafrost geophysicist and professor emeritus at the University of Alaska Fairbanks, who was not involved in the new study. He noted that natural glaciers—vast sheets of ice that creep slowly downhill—exhibit similar behavior through sudden surging and acceleration phases.
The physical evidence left behind at the sites confirmed this bottom-up mechanism. Because the researchers discovered enormous blocks of intact frozen material scattered throughout the debris field, they could definitively determine that the permafrost had failed structurally from below. Had the ground degraded slowly from the surface downward, the landscape would have manifested primarily as vast pools of liquid mud rather than colossal blocks of shattered ice and earth.
Furthermore, the environmental tumult did not conclude with the initial moment of collapse. The sheer volume of displaced material left behind towering walls of exposed permafrost on either side of the slide scars, leaving the freshly exposed frozen earth directly vulnerable to the relentless summer sun.
"Just because you have this large detachment failure, that doesn’t mean it’s over," Young cautioned. "Actually, it means you’ve opened up more potential for failure."
The broader implications of these massive geological disturbances extend far beyond the immediate geography of the Northwest Territories. As permafrost thaws on such a dramatic scale, dormant soil microbes rapidly awaken and begin feasting on the vast amounts of ancient organic material trapped within the matrix, expelling carbon dioxide and methane as metabolic byproducts. Scientists warn this process could ignite a dangerous positive feedback loop, wherein warmer global temperatures cause increased carbon emissions from the thawing north, which in turn drives further planetary warming and subsequent permafrost loss.
"That’s a major global concern," said Miriam Jones, a research geologist who studies permafrost at the United States Geological Survey and was not involved in the recent study. "It’s a feedback that many of us have been studying."
Simultaneously, ecological shifts are compounding the vulnerability of the north. Plant life is rapidly marching northward at rates of miles per decade, a widespread ecological trend known as Arctic greening. In many northern areas, a proliferating density of woody shrubs traps drifting winter snow, effectively insulating the ground and preventing the bitter chill of winter from penetrating deeply enough to protect the underlying permafrost, thereby hastening its long-term decline.
At the same time, this expansion of vegetation provides an abundance of fuel for northern wildfires, which are becoming more frequent and severe. These fires frequently burn deep into the rich layers of peat that have accumulated in the soil over centuries. These persistent anomalies, often referred to by scientists as "zombie fires," are capable of smoldering slowly underground through the freezing winter months beneath blankets of snow, only to reignite during the spring thaw and release even more stored carbon into the atmosphere.
The pressing question facing the scientific community now is how much more planet-warming gas might be spewed into the atmosphere as bacteria proliferate in the raw aftermath of these massive permafrost detachment slides.
"The short answer is: We don’t know how much, because we haven’t characterized and classified it," Young admitted. "But it could be quite severe, just because the size of these features."
Indeed, previous scientific studies have established that even much smaller, localized instances of abrupt permafrost thaw are capable of generating significant, measurable carbon emissions. As researchers continue to monitor the changing Arctic, experts warn that these dramatic landscape failures may only be the beginning.
"I expect that we can see more of these types of surprises," Olefeldt concluded, "as we cross thresholds in other regions that have these vulnerabilities to collapse."