mountain chain, c.700 mi (1,130 km) long, extending S from British Columbia to N Calif., where it becomes the Sierra Nevada; it parallels the Coast Ranges, 100–150 mi (161–241 km) inland from the Pacific Ocean. Many of the range's highest peaks are volcanic cones, covered with snowfields and glaciers. Mt. St. Helens erupted in 1980 in one of the greatest volcanic explosions in U.S. history, and Lassen Peak, 10,457 ft (3,187 m) high, in Lassen Volcanic National Park, is still active. Mt. Rainier (14,410 ft/4,392 m), in Mount Rainier National Park, is the highest point in the Cascades; Mt. Shasta and Mt. Hood are other prominent peaks. The Columbia River flows from east to west across the range. Of the many lakes in the Cascades, Crater Lake, in Crater Lake National Park, and Lake Chelan, in Lake Chelan National Recreation Area, are the most famous. Other federal lands in this popular recreation area are North Cascades National Park, Ross Lake National Recreation Area, and Cascade-Siskiyou and Lava Beds national monuments; national forests cover an extensive area.
Receiving more than 100 in. (254 cm) of precipitation annually, much of it as snow, the Cascades are a major source of water in the NW United States. Hydroelectricity is generated on the western slope; irrigation is used in the fertile eastern side valleys. Timber is the region's chief resource, but a growing concern for ecology and the environment has developed into a major political debate surrounding the trees. The Cascade Tunnel, 8 mi (12.9 km), is one of the longest railroad tunnels in North America.