Canada rides on one of 30 or so tectonic plates, or slabs, which underlie the earth’s continents and oceans. The plates — each tens of kilometres thick — move in different directions, possibly in response to currents of molten material below the earth’s crust. When plates collide, earthquakes and volcanic activity occur. In geological time, collisions uplift mountain chains. Canada’s west coast is situated in one of the world’s most active collision zones, where the westbound North American plate overrides the Pacific plate.
Mountains are often found along coastlines where continental and ocean plates meet. The collision sets off a process in which the ocean plate slides underneath the continental plate, buckling it and uplifting mountains. As the surface buckles, volcanoes force up fiery rock in fractures (faults) and wavy folds. Mountain building is measured in millions of years. Some 250 million years ago, the collision of the North American plate with Europe and Africa built up the Appalachian and Laurentian mountains. Canada’s east coast is relatively calm now, but its west coast lies on the Pacific’s earthquake-prone “ring of fire.” The North American plate began creeping westward 80 to 40 million years ago, eventually colliding with the Pacific plate. The collision compressed sedimentary rocks, thrusting up highly faulted and folded parallel chains from the Rockies to the Coast Mountains. It also created British Columbia’s interior plateau, now the eroded remnant of another ancient range. In the Yukon’s St. Elias Mountains, uplift continues, pushing up Canada’s youngest, loftiest peaks, including its highest — 5,959-metres Mount Logan.
This animation illustrates the movement of the Pacific Ocean and North American Continental tectonic plates; moving arrows indicate their opposing directions, and others label the collision zone between the two plates. As the narration progresses, the animation illustrates how hot, molten rock is pushed upwards by volcanic activity, and smoke rises from the volcano. Labels also indicate parallel mountain ranges when the narration explains how they are formed.
Roughly 30 tectonic plates, each one many kilometres thick, underlie the earth’s surface.
When ocean and continental plates meet, the ocean plate slides underneath the continental, causing the surface to buckle.
Volcanic activity forces fiery rock up into these fractures and folds, forging waves of parallel mountain ranges over millions of years.
Canada’s west coast is situated in one of the world’s most active collision zones. Here, the westbound North American plate overrides the Pacific plate, creating the highly faulted and folded ranges from the Rockies to the Coast Mountains.