Cascade Range

The Cascade Range, or Cascades, is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as many of those in the North Cascades, and the notable volcanoes known as the High Cascades. The small part of the range in British Columbia is referred to as the Canadian Cascades or, locally, as the Cascade Mountains. The highest peak in the range is Mount Rainier in Washington at 14,411 feet (4,392 m).

The Cascades are part of the Pacific Ocean's Ring of Fire, the ring of volcanoes and associated mountains around the Pacific Ocean. All of the eruptions in the contiguous United States over the last 200 years have been from the Cascade Volcanoes. The two most recent were Lassen Peak from 1914 to 1921 and a major eruption of Mount St. Helens in 1980. Minor eruptions of Mount St. Helens have also occurred since, most recently from 2004 to 2008. The Cascade Range is a part of the American Cordillera, a nearly continuous chain of mountain ranges (cordillera) that form the western "backbone" of North, Central, and South America.

The Cascades are home to many national parks and protected areas, including North Cascades National Park, Mount Rainier National Park, Crater Lake National Park, and Lassen Volcanic National Park. The northern half of the Pacific Crest Trail follows the range.

The Cascades extend northward from Lassen Peak (also known as Mount Lassen) in northern California to the confluence of the Nicola and Thompson rivers in British Columbia. The Fraser River separates the Cascades from the Coast Mountains in Canada, as does the Willamette Valley from the upper portion of the Oregon Coast Range. The highest volcanoes of the Cascades, known as the High Cascades, dominate their surroundings, often standing twice the height of the nearby mountains. They often have a visual height (height above nearby crestlines) of one mile or more. The highest peaks, such as the 14,411-foot (4,392 m) Mount Rainier, dominate their surroundings for 50 to 100 miles (80 to 161 km).

The northern part of the range, north of Mount Rainier, is known as the North Cascades in the United States but is formally named the Cascade Mountains north of the Canada–United States border, reaching to the northern extremity of the Cascades at Lytton Mountain. Overall, the North Cascades and Canadian Cascades are extremely rugged; even the lesser peaks are steep and glaciated, and valleys are quite low relative to peaks and ridges, so there is great local relief. The southern part of the Canadian Cascades, particularly the Skagit Range, is geologically and topographically similar to the North Cascades, while the northern and northeastern parts are less glaciated and more plateau-like, resembling nearby areas of the Thompson Plateau.

The range is near the Pacific Ocean and in the region's prevailing westerly winds, so it receives significant rain and snowfall, especially on the western slopes due to orographic lift, with annual snow accumulations of up to 1,000 inches (2,500 cm) (= 83 feet (25 m)) in some areas. Mount Baker in Washington recorded a national record single-season snowfall in the winter of 1998–99 with 1,140 inches (2,900 cm) (= 95 feet (29 m)). Before that year, Mount Rainier held the American record for snow accumulation at Paradise in 1978. It is not uncommon for some places in the Cascades to have over 500 inches (1,300 cm) of annual snow accumulation, such as at Lake Helen, near Lassen Peak. Most of the High Cascades are therefore white with snow and ice year-round. The western slopes are densely covered with Douglas-fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla) and red alder (Alnus rubra), while the drier eastern slopes feature mostly ponderosa pine (Pinus ponderosa), with some western larch (Larix occidentalis), mountain hemlock (Tsuga mertensiana) and subalpine fir (Abies lasiocarpa) and subalpine larch (Larix lyallii) at higher elevations. Annual rainfall is as low as 9 inches (230 mm) on the eastern foothills due to a rain shadow effect.

Beyond the eastern foothills is an arid plateau that was largely formed 17 to 14 million years ago by the many flows of the Columbia River Basalt Group. Together, these sequences of fluid volcanic rock form the 200,000-square-mile (520,000 km²) Columbia Plateau in eastern Washington, Oregon, and parts of western Idaho.

The Columbia River Gorge is the only major break of the range in the United States. When the Cascades began to rise 7 million years ago in the late Miocene, the Columbia River drained the relatively low Columbia Plateau. As the range grew, erosion from the Columbia River was able to keep pace, carving out the gorge and major pass seen today. The gorge also exposes uplifted and warped layers of basalt from the plateau.