Hazards associated with alkaline glaciovolcanism at Hoodoo Mountain and Mt. Edziza, western Canada: comparisons to the 2010 Eyjafjallajokull eruption

The hazards associated with 2010 eruption from Eyjafjallajokull were well documented, and included flooding, pyroclastic activity, and local/regional ash and aerosol dispersal (e.g., Gudmundsson et al, 2010, Session V27). At least two ice-capped, alkaline volcanoes in northwestern British Columbia could produce similar styles of eruptive activity with associated local and regional hazards: Hoodoo Mountain and the Mt. Edziza volcanic complex. Similar to Eyjafjallajokull, both of the Canada volcanoes have likely had multiple Holocene eruptions of lava flows from beneath snow/ice cover, both eruption mildly alkaline basaltic to trachytic lavas, and both also have a history of explosive eruptions. Hoodoo Mountain volcano, which is approximately 17 cubic kilometers in volume, erupts dominantly trachyte-phonolite composition lavas, although it also has closely associated basaltic centers. Most of its history has been dominated by effusive eruptions, but at least one thick sequence of eutaxitic pyroclastic materials has been erupted in the past 50 ka (Edwards et al, 2002). It is presently covered by snow and a 3 km diameter ice cap that feeds a few small, flank alpine glaciers. The Mt. Edziza volcanic complex is much larger, with an estimated total eruptive volume of approximately 650 cubic km; it has had an extended eruptive history during the Plio-Pleistocene (Souther et al, 1984) including basaltic and trachytic eruptions. It presently hosts an ice-filled summit caldera approximately 2.8 by 2 km, which feeds several alpine glaciers radiating outwards in all directions. Edziza has several striking morphological similarities to Eyjafjallajokull, including the similar-sized summit ice cap dominated by silicic eruption products, an overall elongate morphology, and flanking fields of basaltic lava flows. Although Hoodoo and Edziza volcanoes are located in relatively remote parts of British Columbia, eruptions from either would likely partly melt existing snow and ice cover, generating locally important lahars and flooding along major BC water courses (Iskut and Stikine rivers). More importantly, fine silicic ash produced by phreatomagmatic activity could be a significant hazard for North American airspace, just as ash from Alaskan eruptions (e.g. Redoubt 1989/1990) has caused occasional air traffic problems. This possibility has recently been re-enforced by studies of lacustrine-deposited ash across western Canada (Lakeman et al 2008). *Edwards et al (2002) Subglacial, phonolitic volcanism at Hoodoo Mountain volcano, Canadian Cordillera, Bull Volc. DOI: 10.1007/s00445-002-0202-9 *Lakeman et al (2008) Holocene tephras in lake cores from northern British Columbia: Can. J. Earth Sci. 45, 935-947. *Souther et al (1984) Chronology of the peralkaline late Cenozoic Mount Edziza volcanic complex, northern British Columbia, Canada. Geol. Soc. Am. Bull. 95, 337-349.