COLUMBIA RIVER PLATEAU

The 'Columbia River Plateau' is a geologic and geographic region that lies across parts of the U.S. states of Washington, Oregon, and Idaho. It is a wide flood basalt plateau between the Cascade and Rocky Mountains, cut through by the Columbia River. It is also called the 'Columbia Basin'.

Contents

Geology

Geography

See also

References

External links

Geology

During late Miocene and early Pliocene times, one of the largest flood basalts ever to appear on the earth's surface engulfed about 63,000 square miles (160,000 km²) of the Pacific Northwest, forming a large igneous province (the Columbia River Basalt Group). Over a period of perhaps 10 to 15 million years lava flow after lava flow poured out, eventually accumulating to a thickness of more than 6,000 feet (1.8 km). As the molten rock came to the surface, the earth's crust gradually sank into the space left by the rising lava.
The subsidence of the crust produced a large, slightly depressed lava plain now known as the 'Columbia Basin' or Plateau. The ancient Columbia River was forced into its present course by the northwesterly advancing lava. The lava, as it flowed over the area, first filled the stream valleys, forming dams that in turn caused impoundments or lakes. In these ancient lake beds are found fossil leaf impressions, petrified wood, fossil insects, and bones of vertebrate animals.

Geography

The cities in the ''Columbia Plateau'' include:

★ Spokane

★ Davenport

★ Pullman

★ Vantage

★ Yakima

★ Walla Walla

★ Kennewick

★ Richland

★ Pasco
Major tourist attractions include lava flows that were created by the eruptions of the Pliocene and Miocene eras, the Blue Mountains, and the Columbia River.

See also

★ Grand Coulee

★ Channeled scablands

★ Interior Plateau

References

''Portions of this article adapted from works of the United States Government, which are in the public domain''

External links

★ USGS Page on Columbia Plateau

★ Geology of Lake Roosevelt National Recreation Area (source of much of this page)