Volcanism of the Mount Edziza volcanic complex | |
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![]() The Big Raven Plateau at the northern end of the Mount Edziza volcanic complex consists of several lava flows that have issued from multiple volcanoes in the last 7.5 million years | |
Coordinates: 57°30′N 130°36′W / 57.5°N 130.6°W[1] | |
Location | British Columbia, Canada[2] |
Range | Tahltan Highland[3] |
Duration | At least 7.4 million years ago to less than 2,000 years ago[4][5] |
Created | Raspberry Formation (first cycle), Little Iskut Formation (first cycle), Armadillo Formation (first cycle), Nido Formation (second cycle), Spectrum Formation (second cycle) Pyramid Formation (second cycle), Ice Peak Formation (third cycle), Pillow Ridge Formation (third cycle), Edziza Formation (third cycle), Arctic Lake Formation (fourth cycle), Klastline Formation (fourth cycle), Kakiddi Formation (fourth cycle), Big Raven Formation (fifth cycle)[6] |
Rocks | Alkali basalt, hawaiite, trachybasalt, tristanite, mugearite, benmoreite, trachyte, comendite, pantellerite[7] |
The Mount Edziza volcanic complex (MEVC) in British Columbia, Canada, has a long history of volcanism that spans more than 7 million years. It occurred 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 approximately 1,000-square-kilometre (400-square-mile) volcanic plateau forming the base of the MEVC owes its origin to 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 seven rock types are products of varying degrees of magmatic differentiation in underground magma reservoirs. 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. Renewed volcanism could produce explosive eruptions and block local streams with lava flows.
The first magmatic cycle between 7.5 and 6 million years ago is represented by the Raspberry, Little Iskut and Armadillo geological formations, each of which is the product of a different eruptive period. Three distinct periods of eruptive activity also characterized the second magmatic cycle between 6 and 1 million years ago; they are represented by the Nido, Spectrum and Pyramid geological formations. The third magmatic cycle about 1 million years ago is represented by the Ice Peak, Pillow Ridge and Edziza geological formations, each of which is also the product of a distinct eruptive period. Three distinct periods of eruptive activity also characterized the fourth magmatic cycle between 0.8 and 0.2 million years ago which are represented by the Arctic Lake, Klastline and Kakiddi geological formations. The fifth magmatic cycle began at least 20,000 years ago and may be continuing to the present; a single distinct eruptive period of this magmatic cycle is represented by the Big Raven Formation.
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