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. Rockfalls involve a smaller rockmass that disintegrates into numerous blocks that fall, bounce, and roll on steep slopes after detachment. Rockfalls are a constant problem along transportation routes through rocky terrain in Canada and, though small, have resulted in numerous deaths in this century.
Debris flows are smaller and less rapid than rock avalanches but can be very destructive.
They occur when asaturated mass of surficial deposits moves down a steep stream channel. Initial failure is frequently triggered by heavy rains. Debris flows are a major problem in southern British Columbia where numerous defensive structures have been constructed to protect homes and transportation routes. They can also occur following the bursting of a natural dam formed by landslide debris, glacial moraine, or glacier ice. In Klattasine Creek, British Columbia, for example, a massive debris flow was triggered in the early 1970's when a moraine-dammed lake burst in the headwaters of the Creek.