A catastrophic permafrost detachment slide in Canada’s Northwest Territories mobilized 18 million cubic meters of earth, creating a new class of landslide driven by decades-old wildfires and deep underground thawing.
- Permafrost detachment slides occur when deep subterranean layers thaw from below, separating entire frozen blocks of earth rather than melting slowly from the surface.
- Wildfires and extreme summer temperatures weaken the ground surface, opening tension cracks that allow water to infiltrate deep underground over decades.
- Researchers identified more than 150 similar slides in the region via satellite observations, which shows a geological hazard linked to climate warming.
In 2018, an enormous landslide occurred in Canada’s Northwest Territories, displacing a slab of earth roughly equivalent in volume to seven Great Pyramids of Giza, sciencenews.org reported. The event mobilized 18 million cubic meters of earth and dammed the Redstone River. A prior event in 2017 moved 4.5 million cubic meters of material, according to field observations detailed in sciencenews.org.
An analysis reveals that these events represent a new class of catastrophic landslides called permafrost detachment slides, researchers reported in Geophysical Research Letters. According to Dmitry Nicolsky, a geophysicist studying permafrost at the University of Alaska Fairbanks who was not involved in the research, massive landslides usually do not involve such large amounts of still-frozen material, and when they originate within thawing layers, their movement is typically slow.
The inspiration for the research manifested in 2019, when permafrost geologist Joseph Young was helicoptering to a field site in the Northwest Territories, sciencenews.org reported. In some valleys, the slopes were collapsing with landslides everywhere in an area where permafrost should not have been thawing much.
Traditionally, permafrost melts from the top down, releasing a slurry of muddy material, Young told sciencenews.org. At these sites, however, large blocks of still-frozen ground moved hundreds of meters.
“Traditionally with permafrost, it melts from the top down, and that releases this slurry of muddy material,” permafrost geologist Joseph Young said.
Field observations revealed that both the 2017 and 2018 events initiated along flat sliding surfaces roughly 20 meters underground, marking the base of the permafrost layer. Data from satellite monitoring further indicated that ground surfaces at both locations had experienced slow movement of several meters annually over the course of decades. Researchers tracked ground temperature from 2020 to 2022 in undisturbed forests and in areas where wildfires had burned about 25 years earlier.
| Landslide Event | Volume Mobilized | Sliding Depth |
|---|---|---|
| 2018 Redstone River Slide | 18 million cubic meters | ~20 meters underground |
| 2017 Regional Slide | 4.5 million cubic meters | ~20 meters underground |
Computer simulations based on temperature data indicate that wildfire and extreme summer temperatures warm and weaken the frozen ground surface. This process causes the ground to creep and form tension cracks that allow water to penetrate deeper into the frozen subsurface. The water eventually reaches beneath the permafrost layer, causing it to thaw from below and detach entirely, sciencenews.org reported.
More than 150 other slides in the region, identified via satellite observations, may also be permafrost detachment slides, Young told sciencenews.org. This phenomenon can occur wherever there is a relatively thin and warm permafrost layer combined with a rapid warming event. Nicolsky noted via sciencenews.org that scientists must better study what occurs beneath the surface in permafrost regions because researchers do not yet know how the ground will move.
“This is a direct reality of a changing climate,” Young said.
- Permafrost detachment slides study, Geophysical Research Letters, Sept. 28
- Science News reporting on Northwest Territories landslides
