CENTRAL VALLEY

also called the Great Valley, valley, in California, U.S., covering about 18,000 square miles (47,000 square km) and paralleling the Pacific coast for about 450 miles (725 km). Only 40 miles (64 km) in width, it is almost totally enclosed by mountain walls, which include the Klamath Mountains (north), Sierra Nevada (east), Tehachapi Mountains (south), and Pacific Coast Ranges (west). The Sacramento and San Joaquin rivers, which run through the Central Valley, are fed mainly by the abundant rains and melting snows of the Sierra's western flank. The San Joaquin valley in the south embraces more than three-fifths of the entire basin, and the Sacramento valley in the north constitutes the remainder. The most northerly part of the Sacramento valley, extending about 30 miles (48 km) north of the city of Red Bluff, is known as Anderson Valley. The Sacramento and San Joaquin rivers combine southwest of the city of Sacramento in an area known as the Delta Lands to enter San Francisco Bay, the Central Valley's only outlet. The development of ranching and agriculture in the valley progressed rapidly after the California Gold Rush in 1849. Because of the irrigation made possible by numerous dams and canals, the area now contains some of the richest farmland in the United States and produces a wide variety of crops, including cotton, fruits (wine grapes, peaches, apricots), grains (wheat, rice), nuts, sugar beets, and vegetables. The valley is also rich in petroleum and natural gas. Spanish Valle Central, structural depression in central Chile between the Western Cordillera of the Andes and the coastal range, extending for about 400 miles (650 km) from the Chacabuco Range in the north to the river Bo-Bo in the south. The valley is the agricultural heartland of Chile and consists of a 40- to 45-mile- (64- to 72-kilometre-) wide plain made up of a vast thickness of heavily mineralized alluvial soils deposited by the region's principal rivers, the Mapocho, Maule, and Maipo. This central section of Chile enjoys a Mediterranean climate, with the cool, dry summers and mild, rainy winters characteristic of the western coasts of all the continents between 30 and 40 degrees latitude. Vegetation varies with the altitude: near sea level Solanum maritimum, a relative of the potato, is common; up to 2,500 feet (760 m) characteristic plants include a treelike lily (Crinodendron patagua), Bellota miersii, and low trees such as Acacia. The original dry forest, however, has been gradually eliminated by urban and agricultural encroachment. The valley was the original centre of European colonization beginning in the mid-1500s. It continues to be the home of the majority of Chileans and is the predominant agricultural region of the country, containing 40 percent of all its cultivated land. Santiago, the capital and cultural centre of the nation, with a metropolitan-area population of more than 4,200,000, is situated at the northern end of the valley. Three other urban centres of more than 130,000 people, Talcahuano, Chillan, and Temuco, are located to Santiago's south along a longitudinal railroad constructed midway between the Andes and the coastal range; each city was a centre of settlement of Chile's rich agricultural hinterlands outside Santiago. A section of the Chilean portion of the Pan-American Highway runs southward through the valley from San Felipe, and air service connects all major centres.