The hazard posed by landslides can be attributable to the impact of rapidly moving debris, the failure of ground directly beneath a structure, or due to secondary effects such as river damming or landslide-generated waves. Snow avalanches are mass movements of snow downslope and are a considerable hazard in the mountains of Canada particularly to those pursuing recreational activities, such as skiers and mountaineers. In the past, however, they have caused substantial death and destruction to mining and transportation facilities. There are many types of landslides. Rock avalanches, involve the failure and disintegration of a large rockmass on a mountain slope and the rapid movement of this debris downslope and into a valley.
Rock avalanches can be very destructive when they impact on human activity.
Canada's worst landslide disaster occurred at Frank, Alberta, in 1903 when 90 million tonnes of limestone detached from Turtle Mountain and buried part of the coal mining town of Frank resulting in the deaths of about 75 people. Debris avalanches are large rapid mass movements of volcanic rock originating on the slopes of volcanoes. Several have taken place in this century on the Pleistocene volcanoes of the Garibaldi Volcanic Belt, southwestern British Columbia, and are a major hazard in the development of the region. Rockslides occur when a rock mass slides on a detachment surface but does not travel a long distance. Two rockslides which occurred in the nineteenth century in Quebec City resulted in the deaths of 77 people.