These young volcanic centers are just the "tip of the ice berg" of Quaternary volcanism in Canada (Figure 1). Stretching northward from the Cascades, the Garibaldi volcanic belt culminates in a 20 km wide caldera complex at Mount Silverthrone. North of Silverthrone, the east-west trending Anahim volcanic belt shows the trace of a mantle hot spot, most recently active (~7,000 ka) in central British Columbia. Eastern British Columbia is strewn with young centres of alkali olivine basalt, many bearing mantle nodules and the northwestern corner of the province has and is being torn apart by peralkaline volcanic centres which have been active over millions of years. Farther north in Yukon Territory, basaltic centres and flows cover the landscape in many areas.
Much of this wealth of volcanic material still awaits detailed studies. Regional mapping projects delineated the spatial and temporal limits of most of the young volcanic rocks, but few received more than cursory study. Although young flows were noted in 1872 by R.C. Selwyn during his investigations in the Wells Gray-Clearwater area of east central British Columbia, and G.M. Dawson described the White River Ash (Mount Churchill, Alaska) in his 1889 Memoir, the remoteness and difficult terrain of western Canada has discouraged investigation.
Detailed investigations into volcanic processes in Canada started about 50 years ago with the important pioneering 1942 work of Bill Mathews (University of British Columbia) in the Tuya-Teslin country of northern B.C. In a graduate seminar in Berkley California, Bill was assigned a 1931 paper by Richard Fuller which described chilled basalts from the Columbia River Plateau. Bill quickly realized that glacial ice could provide sufficient water depth to produce the flat- topped forms with foreset bedded breccias that he had found in the Tuya-Teslin country. Tuya Butte (in the Tuya Volcanic field, Figure 1) was a particularly well preserved example, thus arose the name "tuya" for these subglacial volcanic landforms.
Bill put many young volcanic landforms on the map. However, his next most notable contribution was his work in the Garibaldi area of south western British Columbia. His studies there included development of techniques for chemical classification using the refractive index of gas produced by melting volcanic rock powder and put Canadian volcanoes on the international map. This work was done in 1947. Garibaldi (Figure 2) is still the only Canadian volcano that consistently shows up on international compilations!
Close on the heels of Bill Mathews was Jack Souther (Geological Survey of Canada - Vancouver (GSC)). He added the several hundred more Quaternary volcanoes to the map of Canada. A regional mapper for most of his career, Jack's work in the Stikine country put Mount Edziza and a host of other centres on the map.
Over the next decade, a much clearer picture of Cordilleran volcanism and tectonics emerged. In 1977 the book, Volcanic Regimes, with a chapter on Cordilleran tectonics by Jack Souther contributed significantly to our early understanding of Quaternary volcanism in Canada. After Bill and Jack, Don Francis (McGill University) and his students carried on notable work in northern B.C. and Yukon. Don's work has focused on the nature of the mantle beneath the northern cordillera, and challenged our earlier notions on the nature of volcanism in the region.
These pioneering workers paved the way for a vibrant and active volcanological community in Canada, but this is only half the story. Many Canadian researchers work in the Archean, where the greenstone belts are the best exposed in the world. Lorne Ayers (University of Saskatchewan) and Maurice Lambert's (GSC - Ottawa) work on the reconstruction of ancient edifices of the Archean and Proterozoic showed that processes then were very similar to those going on today. Bob Baragar's (GSC - Ottawa) work on the Coppermie Flood basalts of the North West Territories proved that the tectonic setting of even these ancient rocks could be determined. In fact greenstone belts expose in cross section by folding and subsequent glacial scour, revealed text-book examples of pillows, volcanic clastics deposits and intrusions.
A traditional of national and international involvement in volcanology, established by these early workers, carries on today. The Geological Association of Canada has a small active group in its Volcanology and Igneous Petrology Division, which meets once a year at the Annual General Meeting of the Society. Here members are often identified, by their research and participation in other activities, to represent the Country on international committees. Many Canadians sit on international committees overseen by learned societies such as the International Union of Geodesy and Geophysics. The Canadian National Committee (CNC) has two members representing each of the branches of IUGG. For each, there is a senior and junior member. Every effort is made to chose people who are active researchers and can be of benefit both to the larger community of volcanologists at home and to the society.
International work has helped Canadians become more aware of the growing threat of volcanoes. In Canada, although some volcanoes pose a significant threat to local communities, and any sizable eruption would impact the economy of western Canada, research is limited. Because no large explosive eruptions have occurred in Canada in the last few hundred years, volcano monitoring is not a priority. Seismic networks, already in place, can be used to identify activity at a Canadian volcano if one were to reawaken, but in many areas, this network will alert authorities only if the impending eruption is potentially large. Additionally, the threat from without seems much greater than the threat from within. Volcanoes in Alaska, Washington, Oregon and California are much more frequently active than those in Canada.
Growing awareness of volcanism, especially the threat from volcanoes to the south and north, have lead to a number of changes in the way Canadians are dealing with volcanic hazards. The near disaster that occurred when a KLM flight over Alaska in December, 1989, flew into an ash cloud from Mount Redoubt, sent echos of concern throughout the international aviation community - enough, in fact, that the question of Canada's readiness to respond to a volcanic crises was raised in the House of Commons. This resulted in the development of a comprehensive plan for dealing with volcanic hazards. Initially the work centered around the aviation hazard issue and Canadians from the aviation industry and regulators were helpful in bringing the hazard to the attention of the International Civil Aviation Organization (ICAO) by lending their voices to those from other countries. This eventually resulted in the adoption and updating of airline procedures in the event of encountering volcanic ash and in the establishment of Volcanic Ash Advisor Centers (VAACs). The Canadian Meteorological Center in Dorval Quebec has recently come online as the VAAC for the North Atlantic to the Pacific.
Although most Canadians remain surprised when they are told that Canada has experienced violent volcanic eruptions in the last few thousand years, plans are in place to protect their safety and that of the aviation industry and flying public. Volcanic research is alive and well in Canada.
Catherine Hickson
Geological Survey of Canada - Vancouver
chickson@nrcan.gc.ca
