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Volcanic eruptions

Volcanoes may seem to be non-existent in Canada. There has been only one documented volcanic eruption in Canada in more-recent historical times, but there are many dormant volcanoes in western Canada particularly in northwestern British Columbia. The entire western Cordillera (BC-Yukon) remains geologically active. Therefore the possibility of an eruption, even a large explosive one, cannot be ruled out.

Quiet as they are, our West Coast volcanoes are part of the "Pacific Ring of Fire" -- a circle that surrounds the Pacific Ocean. These volcanoes vary from small cinder cones to volcanic mountains built up during repeated eruptions. These events have ranged from relatively benign out-pourings of fluid lava (like those in Hawaii) to massive explosions many times larger that the 1980 eruption of Mount St. Helens in Washington state south of Vancouver. Southwestern BC can expect significant accumulations of ash every few hundred years. Mount Churchill, just across the Alaska-Yukon border, erupted 1,300 years ago. It covered 300,000 square kilometres of what is now the Yukon under a blanket of ash, in some areas several metres thick. This eruption was a disaster for the native people and may have led to their mass migration south.

Distribution of significant accumulations of volcanic ash (see map above)
1	St. Helens (508 radiocarbon years ago*)
2	White River (1,200 radiocarbon years ago*)
3	White River (1,500 to 1900 radiocarbon years ago*)
4	Bridge River (2,360 radiocarbon years ago*)
5	St. Helens (3,400 radiocarbon years ago*)
6	Mazama (6,800 radiocarbon years ago*)
7	Glacier River (11,200 radiocarbon years ago*)
---	Extent of volcanic ash distribution
	Major volcanic areas less than 12,000 years old

* Dates are calculated using radiocarbon dating techniques and are not exactly equal to calendar years.

Ash plumes are the major volcanic hazards in Canada

Canada’s most significant volcanic risk comes from explosive eruptions in adjacent Washington and Alaska. Prevailing winds would blow the ash into Canada, as has happened in the past. Ash fallout would cause respiratory ailments for people and a hazard to any technology.