Coast Mountains

Coast Mountains
Coast Range
Mount Waddington.jpg
Coast Mountains with Mount Waddington in middle of far background
Highest point
PeakMount Waddington (British Columbia)
Elevation4,019 m (13,186 ft)
Coordinates51°22′30″N 125°15′30″W / 51°22′30″N 125°15′30″W / 51.37500; -125.25833
Dimensions
Length1,600 km (990 mi) north-south
Width300 km (190 mi) east-west
Area336,962 km2 (130,102 sq mi)
Geography
Rannikkovuoret sijainti.png
Locator map of the Coast Mountains
CountriesCanada and United States
RegionsBritish Columbia, Alaska (part of the U.S) and Yukon
Range coordinates54°N 128°W / 54°N 128°W / 54; -128
Parent rangePacific Coast Ranges

The Coast Mountains are a major mountain range in the Pacific Coast Ranges of western North America, extending from southwestern Yukon through the Alaska Panhandle and virtually all of the Coast of British Columbia south to the Fraser River.[1] The mountain range's name derives from its proximity to the sea coast, and it is often referred to as the Coast Range.[2] The range includes volcanic and non-volcanic mountains and the extensive ice fields of the Pacific and Boundary Ranges, and the northern end of the volcanic system known as the Cascade Volcanoes. The Coast Mountains are part of a larger mountain system called the Pacific Coast Ranges or the Pacific Mountain System, which includes the Cascade Range, the Insular Mountains, the Olympic Mountains, the Oregon Coast Range, the California Coast Ranges, the Saint Elias Mountains and the Chugach Mountains. The Coast Mountains are also part of the American Cordillera—a Spanish term for an extensive chain of mountain ranges—that consists of an almost continuous sequence of mountain ranges that form the western backbone of North America, Central America, South America and Antarctica.

The Coast Mountains are approximately 1,600 kilometres (1,000 mi) long and average 300 kilometres (190 mi) in width.[2] The range's southern and southeastern boundaries are surrounded by the Fraser River and the Interior Plateau while its far northwestern edge is delimited by the Kelsall and Tatshenshini Rivers at the north end of the Alaska Panhandle, beyond which are the Saint Elias Mountains, and by Champagne Pass in the Yukon Territory.[3][4] Covered in dense temperate rainforest on its western exposures, the range rises to heavily glaciated peaks, including the largest temperate-latitude ice fields in the world. On its eastern flanks, the range tapers to the dry Interior Plateau and the subarctic boreal forests of the Skeena Mountains and Stikine Plateau.

The Coast Mountains are part of the Pacific Ring of Fire—the ring of volcanoes and associated mountains around the Pacific Ocean—and contain some of British Columbia's highest mountains. Mount Waddington is the highest mountain of the Coast Mountains and the highest that lies entirely within British Columbia, located northeast of the head of Knight Inlet with an elevation of 4,019 metres (13,186 ft).[5]

Geography

Coast Mountains from the ISS looking north

The Coast Mountains consists of three subdivisions known as the Pacific Ranges, the Kitimat Ranges, and the Boundary Ranges. The Pacific Ranges are the southernmost subdivision of the Coast Mountains, extending from the lower stretches of the Fraser River to Bella Coola. Included in this subdivision is four of the five major coastal icecaps in the southern Coast Mountains. These are the largest temperate-latitude icecaps in the world and fuel a number of major rivers. Other than logging and a large ski resort at the resort town of Whistler, most of the land in the range is completely undeveloped. Mount Waddington, the highest mountain of the Coast Mountains, lies in the Waddington Range of the Pacific Ranges.

Just north of the Pacific Ranges lies the central subdivision known as the Kitimat Ranges. This subdivision extends from the Bella Coola River and Burke Channel in the south to the Nass River in the north.

Kakuhan Range between Juneau and Haines, Alaska

The third and northernmost subdivision of the Coast Mountains is the Boundary Ranges, extending from the Nass River in the south to the Kelsall River in the north. It is also the largest subdivision of the Coast Mountains, spanning the British Columbia-Alaska border and northwards into Yukon flanking the west side of the Yukon River drainage as far as Champagne Pass, north of which being the Yukon Ranges. The Boundary Ranges include several large icefields, including the Juneau Icefield between Juneau, Alaska and Atlin Lake in British Columbia, and the Stikine Icecap, which lies between the lower Stikine River and the Whiting River.

Because the Coast Mountains are just east of the Pacific Ocean, they have a profound effect on British Columbia's climate by forcing moisture-laden air off the Pacific Ocean to rise, dropping heavy rainfalls on the western slopes where lush forests exist.[2] This precipitation is among the heaviest in North America.[2] The eastern slopes are relatively dry and less steep and protect the British Columbia Interior from the Pacific weather systems, resulting in dry warm summers and dry cold winters.[2]

Beyond the eastern slopes is a 154,635 km2 (59,705 sq mi) plateau occupying the southern and central portions of British Columbia called the Interior Plateau. Included within the Interior Plateau is a coalescing series of layered flood basalt lava flows. These sequences of fluid volcanic rock cover about 25,000 km2 (9,700 sq mi) of the Interior Plateau and have a volume of about 1,800 km3 (430 cu mi), forming a large volcanic plateau constructed atop of the Interior Plateau. North of the Interior Plateau on the range's northeastern slopes lies a huge mountainous area known by geographers as the Interior Mountains, which includes the neighbouring Skeena, Cassiar and Hazelton Mountains.

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