Researchers have recorded a rare natural phenomenon in northern Canada: huge monolithic slabs of frozen ground the size of a residential house are sliding down hillsides, infohub.kz reports.
Specialists studied large-scale ground collapses that occurred in the Johnson and Redstone river valleys in Canada's Northwest Territories. Normally, as temperatures rise, permafrost thaws from the top down and turns into viscous mud. In these cases, however, giant intact slabs of earth slid down slopes. A 2017 landslide left a three-kilometer scar on the landscape, and a subsequent event displaced about 4.5 million cubic meters of material. Researchers have named this previously unknown phenomenon permafrost detachment landslides.
The anomaly was caused by thawing from the bottom up. Scientists from the University of Alberta found that rising air temperatures and severe wildfires led to the formation of deep cracks. Water seeped through them for about twenty years and undermined the base of the permafrost layer, which is 20 to 40 meters thick. Losing cohesion with the lower layers, the massive slab slid down the slope as a whole.
In the Mackenzie River valley, researchers found hundreds of similar landslides. Infrastructure in the region has not yet been affected, but the sliding ground has blocked river channels and formed new lakes. The authors of the study predict that as global warming continues and wildfires become more frequent, such collapses will occur increasingly often in northern Canada and Alaska.