PACIFIC MOUNTAIN SYSTEM

series of mountain ranges that constitute a major physical feature of western North America. They run parallel to the Pacific coasts of Washington, Oregon, and California for some 4,500 miles (7,250 km) in the United States and extend north into British Columbia in Canada for about 1,000 miles (1,600 km). The ranges of the system form an elongated H with a closed base. Roughly, from north to south, the west side of the H consists of the mountains of the Queen Charlotte Islands and Vancouver Island, the Olympic Mountains, and the Coast Ranges of Washington, Oregon, and California. The east side of the H is made up of the Coast Mountains of British Columbia, the Cascade Range (itself divided into North, Middle, and South ranges), and the Sierra Nevada (q.v.; often considered to be part of the Pacific mountain system but not included in this discussion). The Klamath Mountains of southern Oregon and northern California are the east-west cross at the centre of the H, while the Transverse Ranges of southern California bend eastward from the Coast Ranges to form the closed base of the H. Inside the H north of the Klamath Mountains are the drowned inside passage of British Columbia, the Puget Sound Lowland of Washington, and the Willamette Valley of Oregon. Inside the H south of the Klamath Mountains is the Central Valley of California. The Pacific mountains act regionally as a barrier to storms from the Pacific Ocean, which especially in winter bring large quantities of precipitation to the western slopes of the ranges. Inland precipitation generally decreases on the east side of the coastal ranges, although it increases again on the western slopes of the Cascades before decreasing drastically on the eastern side. Conifers predominate in the coastal ranges; notable are the giant redwoods from southern Oregon to the Monterey Peninsula of California. Conifers also are dominant inland in the north, giving way to mixed forests of hardwoods and conifers to the south and, farther to the east, an oak-grassland mixture. The most characteristic fauna of the coastal mountains is the anadromous (river-spawning) salmon, although the destruction of spawning habitat threatens its survival. Large land mammals include elk, black bears, deer, and mountain lions; beavers range southward to northern California. Physical features of western North America. Coast Mountains along the Torres Channel, an arm of Atlin Lake, northern British Columbia. series of mountain ranges that stretches along the Pacific coast of North America from northern British Columbia (Canada) to northwestern Mexico. They run for some 4,500 miles (7,250 kilometres) in the United States and extend northward into Canada for another 1,000 miles. The ranges may be divided into eight sections. Roughly from north to south they are the Coast Mountains of British Columbia, the mountains of Vancouver Island and the Queen Charlotte Islands, the Cascade Range (itself divided into North, Middle, and South ranges), the Olympic Mountains, the Coast Ranges of Washington and Oregon, the Klamath Mountains, the Coast Ranges of California, and the Transverse Ranges. For information on the Sierra Nevada, which often are considered to be part of this system, see Sierra Nevada. Additional reading The geography and geology of the Pacific mountain system are treated in James G. Ashbaugh (ed.), The Pacific Northwest: Geographical Perspectives (1994), covering climate, vegetation, agriculture, and the economy; Stewart T. Schultz, The Northwest Coast (1990), a popular, comprehensive view of the people, economy, and landforms of the region; Paul E. Hammond, Guide to Geology of the Cascade Range (1988), a well-written work; John Eliot Allen, Marjorie Burns, and Sam C. Sargent, Cataclysms on the Columbia (1986), a fine overall exploration of the Missoula floods; and A. Jon Kimmerling and Philip L. Jackson, Atlas of the Pacific Northwest, 7th ed. (1985). A good explanation of how the ocean has shaped the Oregon coast, producing different landforms between California and Washington, may be found in Paul D. Komar, Ocean Processes and Hazards Along the Oregon Coast, Oregon Geology, 54(1):319 (January 1992). James G. Ashbaugh