Assessing the relative threats from Canadian volcanoes

This report presents an analysis of the threat posed by active volcanoes in Canada and outlines directives to bring Canadian volcano monitoring and research into alignment with global best practices. We analyse 28 Canadian volcanoes in terms of their relative threat to people, aviation and infrastructure. The methodology we apply to assess volcanic threat was developed by the United States Geological Survey (USGS) as part of the 2005 National Volcano Early Warning System (NVEWS). Each volcano is scored on a number of hazard and exposure factors, producing an overall threat score. The overall threat scores are then assigned to five threat categories ranging from Very Low to Very High. We adjusted the methodology slightly to better suit Canadian volcano conditions by adding an additional knowledge uncertainty score; this does not affect the threat scoring or ranking. Our threat assessment places two volcanoes into the Very High threat category (Mt. Meager and Mt. Garibaldi). Three Canadian volcanoes score in the High threat category (Mt. Cayley, Mt. Price and Mt. Edziza) and two volcanoes score in the Moderate threat category (the Nass River group and Mt. Silverthrone). We compare the ranked Canadian volcanoes to similarly scored volcanoes in the USA and assess the current levels of volcano monitoring against internationally recognised monitoring strategies. We find that even the most thoroughly-studied volcano in Canada (Mt. Meager) falls significantly short of the recommended monitoring level (Mt. Meager is currently monitored at a level commensurate with a Very Low threat edifice, according to NVEWS recommendations). All other Canadian volcanoes are unmonitored (other than falling within a regional seismic network emplaced to monitor tectonic earthquakes). Based on the relative threat and scientific uncertainty surrounding some Canadian volcanoes, we outline five strategies to improve volcano monitoring in Canada and lower the uncertainty about eruption style and frequency: installation of real-time seismic stations at all Very High and High threat volcanoes, comprehensive lithofacies studies at Mt. Garibaldi in order to reduce uncertainty surrounding the frequency and style of volcanism, hazard mapping at Mt. Garibaldi and Mt. Cayley and publication of existing hazard analyses and mapping for Mt. Meager as a comprehensive hazard map, regular satellite-based ground deformation monitoring at all Very High to Moderate threat edifices, and, finally, installation of a landslide detection and alerting system at Mt. Meager.

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