Coast Mountains - Geography

Geography

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.

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. This precipitation is among the heaviest in North America. 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.

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.