Description

The Mount Edziza volcanic complex (MEVC) in British Columbia, Canada, has a history of volcanism that spans more than 7 million years. It has taken place during five cycles of magmatic activity, each producing less volcanic material than the previous one. Volcanism during these cycles has created several types of volcanoes, including cinder cones, stratovolcanoes, subglacial volcanoes, shield volcanoes and lava domes. The roughly 1,000 km2 (400 sq mi) volcanic plateau forming the base of the MEVC originated from the successive eruptions of highly mobile lava flows. Volcanic rocks such as basalt, trachybasalt, benmoreite, tristanite, mugearite, trachyte and rhyolite were deposited by multiple eruptions of the MEVC; the latter six rock types are products of varying degrees of magmatic differentiation in underground magma reservoirs. Renewed effusive volcanism could block local streams with lava flows whereas renewed explosive volcanism could disrupt air traffic with volcanic ash across parts of northwestern Canada. At least 10 distinct flows of obsidian were produced by volcanism of the MEVC, some of which were exploited by indigenous peoples in prehistoric times to make tools and weaponry.