From a helicopter flying over a remote part of Canada’s Northwest Territories, geologist Joseph Young saw something that puzzled him: hillside after hillside that appeared to be collapsing. The slopes weren’t just slipping. In the words he later shared with Science News, they were “just collapsing with landslides everywhere.” The strange pattern led his team to describe a landslide process that scientists hadn’t clearly documented before.
A River Valley Under Pressure
The landscape is the Mackenzie Valley, home to the Mackenzie River, the largest northward-flowing river in North America. It carries water from Great Slave Lake through the Northwest Territories to the Beaufort Sea, and its drainage basin is the second largest on the continent, covering about a fifth of Canada. The valley is the ancestral home of the Dene people, who call the river dehcho, meaning “big river.”
For thousands of years, the ground here has been held together by permafrost, soil, rock and sediment that remains frozen for at least two consecutive years. Warming caused largely by human greenhouse gas emissions is now weakening that frozen foundation.
Two Giant Landslides
Two enormous landslides struck the area, moving roughly 4.5 million and 18 million cubic meters of frozen ground. Landslides themselves aren’t surprising in warming northern regions, where thawing permafrost increases the risk. What puzzled researchers was how these ones behaved.
Normally, permafrost thaws from the top down, turning the surface into a muddy slurry that creeps downhill in a slow landslide. But in the Mackenzie Valley, large blocks of still-frozen ground had traveled hundreds of meters, and early observations suggested the sliding occurred about 20 meters below the surface.
How the Team Explained It
To understand what was happening, Young and colleagues from the University of Alberta installed instruments to monitor ground temperatures over about two years. Their hypothesis was that wildfires, including some that burned decades earlier, together with rising summer temperatures, created tension cracks in the ground. Water seeped into the cracks and began thawing the permafrost from below.
They named these events “permafrost detachment slides” and reported their findings in the journal Geophysical Research Letters. The authors explained that warming and fire work together over decades to push heat deep underground, weakening the base of the permafrost. Exposed ice-rich slopes then keep thawing, triggering more slides and permanently reshaping the landscape.
Other Signs of a Changing Arctic
Thawing permafrost has other effects across the north. In some regions, it releases metals that had been locked in the ground into rivers, turning them bright orange. In Alaska, shifting ground is damaging remote villages, and studies estimate that continued thawing could cause tens of billions of dollars in damage to buildings and roads in the coming decades. Permafrost also stores large amounts of carbon, so its thaw can release greenhouse gases and add to warming.
What the Research Doesn’t Tell Us
It’s important to keep the findings in perspective. The explanation about wildfires and heat is the team’s hypothesis based on observations in one area, and more research is needed to see how widespread these slides are or how often they will occur elsewhere. Predictions of future damage also depend on how quickly the climate warms, so they are estimates, not certainties.
Why It Matters
Permafrost covers vast areas of the Arctic and subarctic, and communities, roads, pipelines and ecosystems depend on its stability. The discovery of a new landslide process shows how quickly the north is changing, and why scientists continue to monitor frozen ground closely.
Seeing the Arctic Responsibly
Nature lovers who want to understand these changes firsthand often compare Arctic wildlife tours, polar expedition cruises and Northwest Territories travel packages that emphasize responsible tourism, invest in proper cold-weather gear such as insulated winter jackets and waterproof hiking boots, and add travel insurance for remote trips. Those who want to support climate research can also look into climate research donations and environmental conservation charities.
Frequently Asked Questions
What is permafrost? Ground that stays frozen for at least two consecutive years.
What is a permafrost detachment slide? A type of landslide in which a block of still-frozen ground slides on a thawed layer beneath it, rather than melting from the top down.
What causes these slides? Researchers suggest that warming and past wildfires create cracks that let water in and thaw the permafrost from below.
Why is permafrost thaw a concern? It can destabilize land, damage buildings and roads, release metals into rivers and release stored carbon.
Sources: Popular Mechanics, Science News, Geophysical Research Letters
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