Natural hazards in the Canadian Cordillera

Important natural hazards in the Canadian Cordillera include earthquakes, volcanic eruptions, landslides, ground subsidence, snow avalanches, floods, and erosion. Earthquakes occur throughout the region, but the seismic risk is highest along British Columbia's populated south coast. Several large volcanoes in western Canada and the adjacent United States have erupted explosively during Quaternary time, producing lahars, pyroclastic flows and surges, as well as plumes of tephra that have blanketed large areas. Considerable damage and loss of life have resulted from rockfalls, rockslides, rock avalanches, and debris flows, and from snow avalanches. Most streams in the Cordillera periodically flood, either as a result of heavy rainfall, rapid melt of snow packs, or the formation and breakup of ice jams. In addition, some very large floods are caused by the sudden draining of moraine- and glacier-damned lakes. Low-lying areas along the British Columbia coast may be flooded by the sea during severe storms, unusually high tides, or as a result of tsunamis. Less important natural hazards in the Cordillera include 1) ground subsidence caused by mining, melt of ground ice, and piping, 2) coastal, lakeshore, and river-bank erosion, and 3) catastrophic gullying.