Permafrost geologist Joseph Young and colleagues have described a kind of landslide that Science News calls new: the permafrost detachment slide, in which a frozen slab breaks free along a flat surface about 20 meters underground and runs downhill. Two slides in Canada’s Northwest Territories set the template, and satellite imagery shows more than 150 other slopes that might behave the same way.
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Young led the work while at the University of Alberta in Edmonton and now works at an engineering firm in the same city. The slides he studied moved millions of cubic meters of ground in a matter of days, a speed that ordinary thaw-driven slope failures take decades to approach. The mechanism links wildfire, heat and water in a sequence that begins years before the ground gives way.
The paper, published September 28 in Geophysical Research Letters, is titled “Permafrost detachment slides: a distinct high-magnitude permafrost mass wasting process” and is available through its digital object identifier record. Science News covered it on November 2 in a report by Nikk Ogasa, which supplies most of the quantitative detail below.
Two slides in the Mackenzie Valley
The template cases sit in the Mackenzie River basin: the Johnson River slide in August 2017 and the Redstone River slide in August 2018. Science News puts the larger of the two at about 18 million cubic meters, a volume it compares with seven Great Pyramids of Giza, and the smaller at about 4.5 million. One slide dammed the Redstone River and created a lake roughly 3.5 kilometers long behind the debris.
A Weather Network summary of the study adds that Steve Kokelj of the Northwest Territories Geological Survey is a co-author and that the sliding moved ground material that conventional permafrost failure would need a few decades to reach “in a matter of days in some cases,” in Young’s words as the outlet reported them. Typical permafrost failures start at the surface and grow over decades, the summary explains, whereas detachment slides fail abruptly from about 20 meters down, which is why the researchers argue they deserve a category of their own rather than a place among thaw slumps.
Fire, cracks and thaw from below
Ordinary permafrost damage runs top-down. As Young told Science News, permafrost traditionally melts from the surface and releases a slurry of muddy material. Detachment slides run the other way. Wildfire or extreme summer heat warms and weakens the surface, which starts slow creep and opens tension cracks. Water seeps through the cracks into frozen ground, thaws the base of the permafrost layer from below, and eventually leaves a slab sitting on a lubricated plane.
Timing is the unsettling part. A 1995 wildfire burned the Mackenzie Valley slopes, and about 20 years later the warming signal had reached the bottom of the frozen layer, according to the account in Grist. Satellite records show both sites had crept by meters per year for decades before the failure, and the researchers’ ground-temperature instruments, run from 2020 to 2022, compared undisturbed forest with ground burned roughly 25 years earlier.
A PermafrostNet document on the central Mackenzie Valley work, authored by Young and University of Alberta colleague Duane Froese, describes the same pattern across a roughly 4,000-square-kilometer study area. It notes that forest fires in the 1990s are closely associated with a rise in slope failures between 2005 and 2020 and argues that past fires preconditioned the landscape for widespread failure.
More than 150 candidate slopes
The 150-plus candidates were flagged from satellite data and have not been confirmed one by one. Science News reports that the slides are most likely where the permafrost layer is thin and warm and a rapid warming event arrives. Young called the findings a direct reality of a changing climate.
Dmitry Nicolsky, a geophysicist at the University of Alaska Fairbanks who was not involved in the study, said the unknown is how the ground will move once it begins: it might go slowly or it might go catastrophically. That uncertainty matters to anyone building pipelines, roads or river crossings on warm, ice-rich slopes. A slide that dams a river also creates a flood threat downstream if the debris dam later fails.
The 2022 study and the open questions
The new paper builds on a 2022 study by Young and colleagues in the same journal on the intensification of permafrost mass wasting in the Mackenzie Valley foothills, which tied recent slope failures to forest fires decades earlier. What the 2026 paper adds is a name and a mechanism for the largest events. Open questions remain on how many of the 150 candidates are true detachment slides and which have warming signals close enough to the permafrost base to fail within years instead of centuries. Satellite screening is how the candidates were found, and the conditions the team names (thin, warm permafrost, a recent burn and years of measurable creep) give a checklist for deciding which slopes to instrument first.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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