The Cascade Range 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, including the rugged spires of the North Cascades, and the notable volcanoes known as the High Cascades. The small part of the range in British Columbia is called the Canadian Cascades or Cascade Mountains; the latter term is also sometimes used by Washington residents to refer to the Washington section of the Cascades in addition to North Cascades, the more usual American term, as in North Cascades National Park.

The Cascades are part of the Pacific Ring of Fire, the ring of volcanoes and associated mountains around the Pacific Ocean. All of the known historic eruptions in the contiguous United States have been from Cascade volcanoes. The two most recent were Lassen Peak in 1914 to 1921 and a major eruption of Mount St. Helens in 1980. Minor eruptions of Mount St. Helens have also occurred, most recently in 2006.

Geography

The northern part of the range, north of Mount Rainier, is known as the North Cascades. It is extremely rugged, with many of the lesser peaks steep and glaciated. The valleys are quite low, resulting in great local relief, and major passes are only about 1,000 m (3,300 ft) high. The southern part of the Canadian Cascades are included in the North Cascades, and have the same geography and geology. Usage differs as to whether to include the Coquihalla Range, which reaches up to the confluence of the Fraser and Thompson Rivers. Its northern reaches have very different terrain and geology, more resembling the plateau country which extends north and east from the range's terminus at Lytton Mountain.

Because of the range's proximity to the Pacific Ocean, precipitation is substantial, especially on the western slopes, with annual accumulations of up to 150 inches (3,800 mm) in some areas—Mount Baker, for instance, recorded the largest single-season snowfall on record in the world in 1999—and heavy snowfall as low as 2,000 feet (600 m). It is not uncommon for some places in the Cascades to have over 200 inches (5,500 mm) of snow accumulation, such as at Lake Helen (near Lassen Peak), one of the snowiest places in the world. Most of the High Cascades are therefore white with snow and ice year-round. The western slopes are densely covered with Douglas-fir, Western Hemlock and Red alder, while the drier eastern slopes are mostly Ponderosa Pine, with Western Larch at higher elevations. Annual rainfall drops to 9 inches (200 mm) on the eastern foothills due to a rainshadow effect.