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.
Mountain range, western U.S. A continuation of the Sierra Nevada, it extends north from Mount Lassen in northeastern California across Oregon and Washington for 700 mi (1,100 km). Its highest elevation is Mount Rainier. Some of the summits, including Mount St. Helens, have erupted in the recent past. The Lewis and Clark Expedition passed through the range in the Columbia River Gorge. Its northern continuation in British Columbia is known as the Coast Mountains. Seealso North Cascades National Park.
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