Volcanism of the Mount Edziza volcanic complex | |
|---|---|
 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 | |
  Mount Edziza volcanic complex Location of the Mount Edziza volcanic complex in British Columbia | |
| 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] |
| Products | Alkali basalt, hawaiite, trachybasalt, tristanite, mugearite, benmoreite, trachyte, comendite, pantellerite[7] |
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.
The first magmatic cycle took place between 7.5 and 6 million years ago and is represented by the Raspberry, Little Iskut and Armadillo 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 ongoing; the single distinct eruptive period of this magmatic cycle is represented by the Big Raven Formation.
- ^ Edwards 1997, pp. 10, 11.
- ^ Yagi & Souther 1974, pp. 820.
- ^ Department of Energy, Mines and Resources 1989.
- ^ Souther et al. 1984, p. 343.
- ^ Souther 1992, p. 253.
- ^ Souther 1992, p. 267.
- ^ Souther & Hickson 1984, p. 79.