A variety of geological and geomorphic processes are potentially hazardous to life and property in the Canadian Cordillera. Natural hazards in this region are mainly products of high relief, high precipitation, and earthquakes. Earthquakes are common in the western Cordillera, especially on the ocean floor off the Queen Charlotte Islands and Vancouver Island, in and adjacent to the Strait of Georgia, and in the Saint Elias and Mackenzie mountains. Much of the seismic activity is closely associated with the interactions of lithospheric plates in the northeast Pacific Ocean. Although most large earthquakes are centred on the ocean floor far from major population centres, a magnitude 7-8+ event could occur close enough to Vancouver, Victoria, or other west coast communities to inflict major damage and some loss of life.
During the Quaternary Period, there have been scores of volcanic eruptions in the western Canadian Cordillera. Most Quaternary volcanic centres in this region are small and have formed through the eruption of low-viscosity, silica-poor magma. Future eruptions of this type probably would have only limited localized effects. In contrast, a few large composite volcanoes have erupted explosively during the Quaternary, producing lahars, pyroclastic flows and surges, as well as plumes of tephra that have blanketed large areas. The most recent eruption of this type occurred near the Alaska-Yukon boundary about 1200 years ago.
Destructive landslides are common in the Canadian Cordillera and are related to instabilities in steep rock slopes and to mountain torrent systems. Most landslide damage and loss of
Figures & Tables
Geology of the Cordilleran Orogen in Canada
Seven stratigraphic chapters cover time slices from Precambrian to Neogene; also included are chapters covering tectonic framework, paleomagnetism, physiographic evolution, Quaternary glaciation, volcanic and plutonic regimes, metamorphism, structural styles, metallogeny, energy and ground resources, and natural hazards. A tectonic synthesis chapter and a summary of outstanding problems round out the volume. Accompanying plates include physiographic, tectonic assemblage, terrane and metamorphic maps, correlation charts, structural cross sections, and special maps showing distribution of Proterozoic and Miocene plutonic suites and the metallogeny of terranes.