Thawing ground created novel type of large landslide in northern Canada

Science News reported that researchers have identified a new type of large landslide, termed a permafrost detachment slide, which occurs when frozen ground thaws from underneath. In 2018, an enormous landslide occurred in the Northwest Territories of Canada, moving a slab of earth equal in volume to approximately seven Great Pyramids of Giza downhill. The event dammed the Redstone River in the Mackenzie Valley, which created a lake 3.5 kilometers long and left behind a barren scar in the forested landscape. [1]

The mechanism of a permafrost detachment slide involves large slabs of frozen soil thawing from below and subsequently sliding downhill. Science News reported that wildfires and underground water can dislodge these large chunks of frozen earth. Researchers were initially puzzled by the 2018 slide because the event initiated in frozen ground that had previously remained glued in place. [1]

Permafrost is defined as soil or sediment that remains continuously below zero degrees Celsius for two years or more, as FTMQ Science reported earlier. Long-term studies on thawing permafrost, such as a 20-year survey near Umiujaq, Québec, have previously documented cumulative ground subsidence of up to 3.8 meters using ground surveys, LiDAR, and drone photography. [4]

The discovery illustrates how sub-surface thermal changes in frozen regions can trigger massive structural failures on slopes. Science News noted that underground water and fire activity contribute to dislodging frozen ground, altering arctic and subarctic terrain. [1]