Coast Mountains

Coast Mountains

Coast Mountains, range, W British Columbia and SE Alaska, extending c.1,000 mi (1,610 km) parallel to the Pacific coast, from the mountains of Alaska near the Yukon border to the Cascade Range near the Fraser River. Mt. Waddington (13,260 ft/4,042 m) is the highest peak. The geologically complex range, composed mainly of metamorphic rocks, slopes steeply to the Pacific Ocean, where the shoreline is deeply indented by fjords. The Coast Mts. have been heavily eroded by mountain glaciers; numerous rivers, including the Fraser, the Skeena, and the Stikine, have cut deep gorges across the range. The average annual precipitation of c.90 in. (230 cm) makes the region one of the wettest parts of Canada. Its slopes are heavily forested, and lumbering is important. In the Coast Mts. is Kemano, one of Canada's largest hydroelectric plants. The Coast Mts. are sometimes confused with the geologically distinct Coast Ranges.
The Coast Mountains are a mountain range of the Pacific Cordillera, running along the north western shore of the North American continent, extending south from the Alaska Panhandle and covering most of coastal British Columbia. They are part of a larger grouping, the Pacific Coast Ranges, which includes the Alaska Range, the Chugach Mountains, the Saint Elias Mountains, the Cascade Range, the Sierra Nevada and the Sierra Madre Occidental in Mexico.

The Coast Mountains are approximately 1600 km long and average 200 km in width. Its southern and southeastern boundaries are described by the Fraser River and the Interior Plateau. North of the Nechako Diversion, the Coast Mountains are flanked on the inland side by the Hazelton Mountains, the Skeena Mountains, the Stikine Plateau and the Tahltan and Tagish Highlands. Its far northwestern edge is delimited by the Kelsall River at the north end of the Alaska Panhandle, beyond which are the Saint Elias Mountains.

Covered in dense temperate rainforest on its western exposures, the range rises to heavily glaciated peaks, including the largest temperate-latitude icefields in the world. It then tapers to the dry interior plateau on its eastern flanks, or to the subarctic boreal forest of the Skeena Mountains and Stikine Plateau.

Mount Waddington, at , is the highest peak in the Coast Mountains and also the highest peak entirely within British Columbia.

Although the Coast Mountains are commonly considered to be the westernmost range of the Pacific Cordillera, the Insular Mountains are the true westernmost range, which includes Vancouver Island and the Queen Charlotte Islands.

The largest icefield in the Coast Mountains is the Ha-Iltzuk Icefield.

Tectonic origin

The Coast Mountains has its origins with a formerly active volcanic arc, called the Coast Range Arc, which began forming about 100 million years ago. Over millions of years, the volcanoes of the Coast Range Arc had their summits worn down and isostatic rebound has caused their solidified magma chambers to rise, forming the Coast Mountains.

During the early to middle Miocene, the Coast Mountains were favored thermally-driven uplift arising from the Miocene passage of the Anahim hotspot beneath the range, and response to convergence in late Miocene-Pliocene time.

Significant peaks

Mountain/Peak Height (metres) Prominence (metres) Location
Mount Waddington 4019 3289
Monarch Mountain 3555 2930
Razorback Mountain 3183 2253
Skihist Mountain 2968 2463
Mount Ratz 3090 2430
Mount Queen Bess 3298 2355
Wedge Mountain 2892 2249
Otter Mountain 2692 2242
Mount Silverthrone 2860 974
Kwatna Peak 2290 2225
Scud Peak 2987 2172

Subranges

The Coast Mountains are subdivided into numerous mountain ranges:


References

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