Mount Garibaldi: hazard potential from a long-dormant volcanic system in the Pacific Northwest

Abstract

Mount Garibaldi Volcanic System (MGVS) is the southernmost member of Garibaldi Volcanic Belt (GVB), the northern (Canadian) segment of the Cascade Volcanic Arc. Temporally episodic explosive to effusive eruptions may be associated with peak ice unloading after glacial maxima. Rapid and widespread deglaciation of the overlying ice sheet, and glacial rebound, have altered the physical characteristics of the landscape whilst the system is thought to have been in long repose for over 10 000 years. Over the last 60 years, the region has become heavily populated due to increased tourism and all-season recreation opportunities. MGVS poses the greatest volcanic threat to the human population and built infrastructure between Vancouver and the resort municipality of Whistler. We believe that this system is a priority for further scientific research, given that its already “very high” overall threat score would likely increase if there was a better understanding of its eruptive history and hazards. Using published and field evidence, we show that potential hazards, related to the volcanic environment of this system, to the settlement of Squamish include voluminous lava flows, pyroclastic density currents triggered by lava dome collapse, tephra fallout, debris flows, and lahars. As relatively few exposures in the system have been dated using modern geochronological techniques, we take this opportunity to (re)calibrate published radiocarbon ages of relatively recent eruptions in GVB.