Cascade Range

The Cascade Range is a mountainous region famous for its chain of tall volcanoes called the High Cascades that run north-south along the west coast of North America from British Columbia to the Shasta Cascade area of northern California. The small part of the range in British Columbia is called the Cascade Mountains.

Geography

At its southern end the range is about 30 to 50 miles (50 to 80 km) wide and 4500 to 5000 feet (1370 to 1520 m) high but is higher and 80 miles (130 km) wide in northern Washington. The tallest volcanoes of the Cascades (called the High Cascades) dominate the rest of the range, often standing twice the height of the surrounding mountains and thus often have a visual height of a mile (1.6 km) or more. The tallest peaks, such as the 14,411 foot (4392 m) high Mount Rainier, dominate their surroundings for 50 to 100 miles (80 to 160 km).

Related Topics:
Washington - Mount Rainier

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The northern part of the range, north of Mount Rainier is extremely rugged, with many of the lesser peaks steep and glaciated. The valleys are quite low however, and major passes are only about 1000 m (3300 ft) high.

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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 (3800 mm) in some areas—Mount Baker, for instance, apparently recorded the largest single-season snowfall on record in the world in 1999—and heavy snowfall as low as 2000 feet (600 m). 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 8 inches (200 mm) on the eastern foothills due to a rainshadow effect.

Related Topics:
Pacific Ocean - Mount Baker - 1999 - Douglas-fir - Western Hemlock - Red alder - Ponderosa Pine - Western Larch - Foothill - Rainshadow effect

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Beyond the foothills is an arid plateau that was created 16 million years ago as a coalescing series of layered flood basalt flows. Together these sequences of fluid volcanic rock form a 200,000 square mile (520,000 km2) region out of western Washington, Oregon, and parts of Northern California and Idaho called the Columbia River Plateau .

Related Topics:
Arid - Basalt - Volcanic rock - Washington - Oregon - Northern California - Idaho - Columbia River Plateau

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The gorge created by the Columbia River is the only major break in the American part of the Cascades. When the Cascades started to rise 7 million years ago in the Pliocene, the Columbia River drained the relatively low Columbia River Plateau. As the range grew, the Columbia was able to keep pace, creating the gorge and major pass seen today. The gorge also exposes uplifted and warped layers of basalt from the plateau.

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Another major pass was cut by the Fraser River through mainly non-volcanic rocks in the British Columbian part of the range. This group of mountains are often called the "Coast Mountains" but are in fact structurally part of the Cascades. Mount Garibaldi and its associated group of volcanoes are in this part of the range. The country rocks here were derived from a mini-continent that grafted itself to this part of North America 50 million years ago, carrying along its own subduction zone (see Juan de Fuca Plate).

Related Topics:
Fraser River - British Columbia - Mount Garibaldi - Continent - Subduction zone - Juan de Fuca Plate

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See also:

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