Volcanoes in Canada

Sunday, May 24, 1992

Catherine Hickson

Volcanoes in Canada? Yes! Canada’s western margin is geologically extremely active. This activity is the result of living on the edge of the huge North American continent, actually a giant tectonic "plate". Off the coast of British Columbia this plate runs into another tectonic plate. The jamming together of these plates creates earthquakes and volcanoes! (Figure 1 on previous page).

A volcano is a place where molten rock, called lava, and gas flow from the earth’s interior onto the surface. A mountain is built up around the vent by the accumulation of rock material emitted by the volcano. These can be small mounds, referred to as cinder cones, or huge mountains, such as Mount Meager, 180 km north of Vancouver.

Volcanoes occur where the earth’s crust is being stretched and pulled apart, and new crust is formed, such as along the undersea Juan de Fuca Ridge west of Vancouver Island. These areas of stretching can also occur on the continents. Such a region is found in north western British Columbia and forms a chain of volcanoes referred to as the Stikine Volcanic Belt. One of the most notable volcanoes in this chain is Mount Edziza, now a provincial park because of its incredible beauty.

Volcanoes can also occur where there is an upwelling of molten material in the earth’s mantle called a "hot spot". Hawaii is not only a tropical hot spot, it is a volcanic one as well! British Columbia has it’s own hot spot in the chain of volcanoes which stretch across the middle of the province, referred to as the Anahim Volcanic Belt. The most recent activity in these belts was a few thousand years ago at a cinder cone called Nazko Cone.

The third type of volcanic area forms where ocean crust is pushed down below continental crust in what is called a subduction zone. A subduction zone runs along the coast of North America from northern California to the northern end of Vancouver Island. The most recently active volcano in this chain is Mount St. Helens in Washington State. Volcanoes in Canada which are part of this chain include Mount Garibaldi, Mount Cayley and Mount Meager. Of these, the most recently active is Mount Meager which has a very large eruption (probably similar to the 1980 eruption of Mount St. Helens) about 2,300 years ago. This eruption spread ash across British Columbia into Alberta.

Although we in Canada have not experienced a major volcanic eruption in many centuries, the processes which created the volcanoes are still active. A volcano may sleep for many centuries as pressure slowly builds up in subterranean magma chambers. However, before an eruption the increasing pressure creates many small earthquakes which are detected at seismography stations and warn of the eruption to come.