Anahim Volcanic Belt

The Anahim Volcanic Belt is a 600 km (373 mi) long volcanic belt, stretching from just north of Vancouver Island to near Quesnel, British Columbia, Canada. The Anahim Volcanic Belt has had three main magmatic episodes: 15–13 Ma, 9–6 Ma, and 3–1 Ma. The volcanoes generally become younger eastward at a rate of 2 cm (0.8 in) to 3.3 cm (1.3 in) a year. The Nazko Cone, which last erupted only 7,200 years ago, is the youngest Anahim volcano. These volcanoes are thought to have formed as a result of the North American Plate sliding westward over a long-lived center of upwelling magma called the Anahim hotspot. The hotspot is thought to be similar to the one feeding the Hawaiian Islands.

Future volcanism is most likely in the form of basaltic cinder cones, but eruptions of less mafic magma, typical of the eastern portions of the belt, cannot be ruled out. A series of earthquakes began October 9, 2007 in the vicinity of Nazko Cone which was related to intense subterraenean volcanic activity in the area.

The volcanic belt is defined by 37 Quaternary basalt centers and three large shield volcanoes called the Rainbow Range, Ilgachuz Range and the Itcha Range. These three large volcanoes have built up dome-like piles of lava and fragmental rocks to a height of 8,130 feet (2,478 m) at Tsitsutl Peak in the Rainbow Range, 7,873 feet (2,400 m) at Far Mountain in the Ilgachuz Range, and 7,760 feet (2,365 m) at Mount Downton in the Itcha Range. The Rainbow Range is a low dome-like cone about 20 miles (32 km) diameter, with Anahim Peak an obsidian plug on its north-east flank. The Ilgachuz Range is 15 miles (24 km) or more in diameter, and the Itcha Range is 10 miles (16 km) wide and about 40 miles (64 km) long. All have been dissected by late Tertiary, pre- stream erosion.

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