Known as permafrost detachment slides, these landslides may be a long-term impact of wildfires
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Researchers have discovered a new type of landslide in Canada’s Northwest Territories, where large blocks of permafrost the size of a two-storey house break off and slide downhill.
These landslides, known as permafrost detachment slides, have not been seen before and appear to result from wildfires in northern latitudes.
In total, researchers found more than 150 instances of these landslides in the area, each typically moving more than one million cubic metres (35 million cubic feet) of land.
Researchers focused on two landslides, one in the Johnson River in 2017 that moved more than 18 million cubic metres (636 million cubic feet) of soil and rock. Another, located in the Redstone River Valley, moved around 4.5 million cubic metres (159 million cubic feet) of debris in 2018.
According to Joseph Young, lead author of the study published in Geophysical Research Letters and PhD student at the University of Alberta, wildfires began these ‘large and quick’ landslides, with the area burning ‘quite severely’ in 1995.
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Wildfires completely eradicate organic material, affecting the top layer of permafrost.
‘[Permafrost detachment slides] can move the amount of material, which would take standard ways of permafrost failure a few decades to reach, in a matter of days in some cases,’ said Young.
What is permafrost?
Permafrost, also known as permanently frozen ground, is soil, sand, sediment or rock that remains at or below 0°C for at least two years.
In total, permafrost covers about 23 million square kilometres (nine million square miles), or about 25 per cent of the Northern Hemisphere’s exposed land surface. Approximately 65 per cent of permafrost is found in Eurasia, while the other 35 per cent is in North America and Greenland.
As the planet warms due to climate change, microbes begin to decompose plant material in the soil, producing greenhouse gases such as carbon dioxide and methane that further warm the planet. Research shows that the volume of permafrost within the upper two metres of the ground will decrease by up to 40 per cent with every 1°C rise in global surface air temperature.
This melting can destabilise the ground, affecting infrastructure and transport. If global warming continues, up to 50 per cent of critical infrastructure around the Arctic is expected to be at high risk by the middle of the century.
Thawing permafrost threatens humans and animals. Bacteria and viruses trapped in ice and soil can cause illness, and scientists have discovered microbes more than 400,000 years old in thawed permafrost.
Warmer years have been linked to a higher risk of previously frozen anthrax bacteria and anthrax outbreaks.
