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. In common usage, the term 'Columbia Basin' refers to more or less the same area as the Columbia Plateau. [Floyd, Ben, et al. " [http://www.co.benton.wa.us/pl/iap/html/body_glossary.htm Glossary] ". (1998) [http://www.co.benton.wa.us/pl/iap/iapindex.htm Hanford Reach Protection and Management Program Interim Action Plan] . Prosser, Washington: Benton County Planning Department.]

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. [http://vulcan.wr.usgs.gov/Volcanoes/ColumbiaPlateau/description_columbia_plateau.html Description: Columbia Plateau Columbia River Basalt.] United States Geologic Survey, accessed October 9 2007.] 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. Entities that have been found in these lake beds are fossil leaf impressions, petrified wood, fossil insects, and bones of vertebrate animals.

Geography

The Washington cities in the Columbia Plateau include:
*Davenport
*Kennewick
*Pasco
*Pullman
*Richland
*Spokane
*Walla Walla
*Yakima

Oregon cities in the Columbia Plateau include:
*Hermiston
*Hood River
*Pendleton
*The Dalles

Points of interest

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.

ee also

*Grand Coulee
*Channeled scablands
*Interior Plateau
*Columbia River Basalt Group

References

External links

* [http://vulcan.wr.usgs.gov/Volcanoes/ColumbiaPlateau/framework.html USGS Page on Columbia Plateau]
* [http://www.nps.gov/laro/webdirectory/geology.htm Geology of Lake Roosevelt National Recreation Area (source of much of this page)]
* [http://harvester.lib.utah.edu/wwdl/index.php/browse/guide/columbia Guide to digital documents and photographs about the Columbia River area.]
* [http://www.vancouver.wsu.edu/crbeha/ Columbia River Basin Ethnic History Archive]