At least five volcanoes have had seismic activity since 1985, including the Mount Edziza volcanic complex (eight events), Castle Rock (two events), Hoodoo Mountain (eight events), Crow Lagoon (four events) and The Volcano (five events). Seismic data suggests that these volcanoes still contain living magma chambers, indicating possible future eruptive activity. Although the available data does not allow a clear conclusion, these observations are further indications that some Northern Cordilleran volcanoes are potentially active and that their associated hazards may be significant. The seismic activity correlates both with some of Canada's most youthful volcanoes and with long-lived volcanoes with a history of significant explosive activity, such as Hoodoo Mountain and the Mount Edziza volcanic complex. To date, Edziza and Hoodoo pose the greatest threats in the Northern Cordilleran Volcanic Province. A large pumice deposit scattered throughout the Edziza complex highlights one of the significant volcanic hazards associated with the complex, including the possibility of a large explosive eruption. This large pumice deposit indicates that the Mount Edziza volcanic complex has a history of producing not only fluid and passive basaltic lava flows, but also more silica-rich trachytic and rhyolitic lava flows and explosive eruptions. The silica-rich compositions are similar to those associated with the most catastrophic eruptions on Earth. A large explosive eruption at the Edziza complex could produce an eruption column that would affect parts of the Pacific Northwest. Similarly, high eruption columns from Hoodoo Mountain would disrupt air traffic between Canada, Alaska and Asia. The flat summit of Hoodoo Mountain is also covered by an ice cap more than thick. An eruption from Hoodoo's summit would cause considerable melting of the ice cap to create large floods and lahars, which would have significant effects on adjacent river valleys. This includes the Iskut River just on the southern flank of Hoodoo Mountain, which is the host for a large amount of salmon, logging operations and a large mining and mineral exploration camp. Edziza and Hoodoo Mountain are two of the three most hazardous volcanoes in Western Canada that have been active in the past 10,000 years, the other being the Mount Meager massif in the Garibaldi Volcanic Belt of southwestern British Columbia which produced a large-scale eruption 2,350 years ago that sent ash as far as central Alberta.