Ilgachuz Range
| Ilgachuz Range | |
|---|---|
Satellite image of the Ilgachuz Range
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| Highest point | |
| Peak | Far Mountain |
| Elevation | 2,410 m (7,910 ft) |
| Coordinates | 52°47′12.1″N 125°19′23.9″W / 52.786694°N 125.323306°W |
| Geography | |
| Country | Canada |
| Province | British Columbia |
| District | Range 3 Coast Land District |
| Range coordinates | 52°46′N 125°18′W / 52.767°N 125.300°WCoordinates: 52°46′N 125°18′W / 52.767°N 125.300°W |
| Parent range | Chilcotin Plateau |
| Borders on | Rainbow and Itcha Range |
| Geology | |
| Formed by | Shield volcano |
| Orogeny | Anahim hotspot volcanism |
| Age of rock | 6.1 to 4.0 million years |
The Ilgachuz Range is a name given to an extinct shield volcano in British Columbia, Canada. It is not a mountain range in the normal sense, because it was formed as a single volcano that has been eroded for the past 5 million years. It lies on the Chilcotin Plateau, located some 350 kilometres (220 mi) north-northwest of Vancouver and 30 km north of Anahim Lake. The highest peak of the range is Far Mountain. The range supports a unique grassland ecosystem. This type of grassland has not been seen anywhere else in central and southern British Columbia. The climate is cool and dry; typical of higher elevations of the Interior Plateau.
The 280 kilometres (174 mi) long West Road River rises in the Ilgachuz Range and flows east to its confluence with the Fraser River between Prince George and Quesnel. It drains an area of approximately 12,000 km2, and dropping over 900 m before joining with the Fraser.
The Ilgachuz Range began erupting 6.1 million years ago and has grown steadily since then. Like all of the Anahim volcanoes, the Ilgachuz Range has its origins in the Anahim hotspot—a plume of magma rising from the Earth's mantle in central British Columbia. The hotspot remains in a fixed position, while the North American Plate drifts over it at a rate of 2 to 3.3 centimetres per year. The upwelling of the hot magma creates volcanoes, and each individual volcano erupts for a few million years before the movement of the plate carries it away from the rising magma. However, where hotspots occur under continental crust, basaltic magma is trapped in the less dense continental crust, which is heated and melts to form rhyolites. Due to their high content of crystals and gasses, rhyolites initiate violent eruptions, though their water content is low and they have a relatively low temperature (around 800-900°C when erupted, whereas basalt can have a temperature of over 1200°C)..
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