The 'Coast Mountains' are the westernmost
range of the
Pacific Cordillera, running along the south 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.
The Coast Mountains were formed when an active
volcanic arc, called the
Insular Islands, collided against the
Pacific Northwest about 115 million years ago. Over millions of years, the Insular Islands 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.
Mount Waddington, at 4,019 metres or 13,186 feet, is the highest peak in the Coast Mountains and also the highest peak entirely within
British Columbia.
The largest
icefield in the Coast Mountains is the
Ha-Iltzuk Icefield.
Significant peaks
Subranges
There are several subdivisions of the Coast Mountains. These include:
★ The
Boundary Ranges, which lie along the BC-Alaska border from the mouth of the
Nass River to the
Chilkoot Pass and include the vast
Juneau Icefield and the even vaster
Stikine Icecap.
★ The
Kitimat Ranges, which lie between the
Nass and
Bella Coola
★ The
Pacific Ranges, which lie between
Bella Coola and the
Lower Mainland. The Pacific Ranges contain the largest temperate-latitude icecaps in the world, each 25-40 km in diameter. These include the Ha-Iltzuk (Silverthrone), Klinaklini, Monarch, Waddington, Homathko, Lillooet and Pemberton Icecaps.
★ The
Chilcotin Ranges, which run on the inland lea of the Pacific Ranges between the head of the
Klinaklini River and the confluence of the
Bridge River and
Fraser River near
Lillooet. The Chilcotin Ranges are sometimes considered part of the Pacific Ranges.
★ The
Lillooet Ranges, lying between the Harrison-Lillooet drainage and the Fraser River, south of the
BCR line. The Lillooet Ranges are sometimes considered part of the Pacific Ranges.
★ The Front Ranges, which include the
North Shore Mountains of
Greater Vancouver and the coastal-lying lower ranges of the
Sunshine Coast and skirting the coastal archipelago.
There are innumerable smaller named ranges, and informal names for many groupings, within these subdivisions. Some neighbouring ranges can be found in
Interior Plateau and the
Hazelton Mountains section of the
Skeena Mountains (which are not part of the Coast Mountains but just inland).
External links
★
Canadian Mountain Encyclopedia Coast Mountains entry
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