Geohazards are geological and environmental conditions that have the potential to impact:
- infrastructure;
- public safety; and
- our environment.
Landslides occur in a variety of settings in the Yukon. These have the potential to cause loss of life or property. We can help create a safer environment in the Yukon by understanding landslides. This includes climate change factors,
Landslides related to permafrost thaw occur throughout the Yukon. These are more prevalent in south and central Yukon. These landslides are unique because of:
- size;
- longevity;
- movement; and
- natural occurrence.
We have done long-term monitoring on many of these landslides. This includes:
- 10 Mile Creek near Carmacks; and
- several slides near Little Salmon Lake.
People travelling across or near glaciers may encounter:
- crevasses;
- icefalls;
- ice avalanches;
- calving; and
- loose or unstable moraines.
In mountainous terrain, glaciers gradually erode away the bases of valley sides. These become steeper and more prone to large landslides. Landslides, such as the 2007 Mount Steele landslide, can travel several kilometres.
Surging glaciers can cross rivers creating a dam and a temporary lake. The dam can later burst causing the lake to drain in a sudden flood. More than 100 glaciers in the St. Elias Mountains are classified as surging glaciers. Lowell Glacier and Tweedsmuir Glacier are 2 well-known surging glaciers that flow into the Alsek River valley.
Earthquakes in the Yukon are usually caused by tectonic plate movement off the coast of southeastern Alaska. As the plates move past each other, earthquakes are triggered along the faults.
Yukon’s historical earthquake record extends back to 1897. Records show that since then a few hundred earthquakes occur per year. Most are rarely felt (less than magnitude 4). Moderate to large earthquakes (greater than magnitude 5) are infrequent. These occur once every few years on average. The largest earthquake ever recorded was magnitude 8 and occurred in 1899 near the southwestern corner of the Yukon.
Permafrost is ground that remains frozen for longer than 2 consecutive years. It may or may not contain significant amounts of ice.
In southern Yukon, less than 25% of the land area contains permafrost. In central Yukon, the distribution of permafrost is more extensive but still discontinuous (frozen layer of soil with areas of thaw during the summer). North of Dawson, it's nearly continuous (layer of soil that's permanently frozen all year).
Permafrost is generally thicker and colder as you move farther north. It may be more than 300-metres thick and colder than -3°C in parts of the North Slope. Around Whitehorse, permafrost is only a few metres thick and is barely below 0°C.
The Yukon Geological Survey works on long-term monitoring projects that:
- support natural hazard risk management; and
- land-use planning.
Community mapping
Hazard maps are being created for Yukon communities. These will assess potential risks from the surrounding landscapes and landforms.
Finished maps are available for these communities:
GIS data for the above open file maps:
The Yukon landforms atlas
This story map features:
- 11 different periglacial landforms commonly found in Yukon; and
- a classified permafrost map.
This was created as a joint effort between the Yukon Geological Survey and Crystal Huscroft of Thompson Rivers University.