GRAN CHACO

alluvial plain in the interior of south central South America, a vast, arid, lowland bounded by the Andes Mountains on the west, by the Paraguay and Paran rivers on the east, generally by the Llanos (plains) de Chiquitos and Baados de Izozog, a marshy area in Bolivia on the north, and on the south by the Ro Salado in Argentina. Its area is about 280,000 sq mi (725,000 sq km). The Gran Chaco has a widely scattered population of indigenous Indian groups including the Guaicur, Lengua, Mataco, Vilela, Zamuco, and Tup. The following article summarizes information about the Gran Chaco; for full details, see South America: Gran Chaco. Because of its alluvial character, the Gran Chaco is composed of extremely deep (up to 10,000 ft ) unconsolidated sandy and silty sediments. Most of the Chaco is poorly drained. All but the extreme northwestern sector is drained by the west-bank tributaries of the Paraguay and Paran rivers. Gran Chaco's climate varies from tropical in the north to warm and temperate in the south. Average temperatures range from 65 to 75 F (18 to 25 C); the highest average annual rainfall is in the east, with 52 in. (1,320 mm). The eastern Chaco is characterized by clustered trees and shrubs interspersed with tall herbaceous savannas. To the west a wide transition zone grades into a dry forest of spiny, thorny shrubs and low trees. Chaco's wildlife is abundant. Among the large animals are the jaguar, puma, tapir, giant armadillo, capybara, red wolf, and guanaco. Reptiles are numerous with a variety of lizards, and there are at least 60 known species of snake. Cattle grazing and cotton raising are the major economic activities in the Chaco. In the eastern Chaco large industrial plants have been established to process tannin. The other major economic activity is forestry, producing lumber and heavy timbers. lowland alluvial plain in interior south-central South America. The name is of Quechua origin, meaning "Hunting Land." Largely uninhabited, the Gran Chaco is an arid subtropical region of low forests and savannas traversed by only two permanent rivers and practically unmarked by roads or rail lines. It is bounded on the west by the Andes mountain ranges and on the east by the Paraguay and Paran rivers. The Chaco's northern and southern boundaries are not as precise: it generally is said to reach northward to the Izozog Swamps in eastern Bolivia and southward to about latitude 30 S, or roughly the Salado River in Argentina. Thus defined, the Gran Chaco extends some 450 miles (725 kilometres) from east to west and about 700 miles from north to south and covers about 280,000 square miles (725,000 square kilometres); of this total, slightly more than half lies within Argentina, a third in Paraguay, and the remainder in Bolivia. The two permanent rivers of the Gran Chaco, the Pilcomayo and the Bermejo (Teuco), flow southeastward across the plain from their Andean headwaters to the Paraguay River and demarcate the three main regional divisions of the Chaco in Paraguay and Argentina: the Chaco Boreal north of the Pilcomayo, the Chaco Central between the two rivers, and the Chaco Austral south of the Bermejo; the portion of the Chaco in Bolivia commonly is called the Bolivian Chaco. Additional reading Literature in English for the Gran Chaco is scarce. Early descriptions include Luis Jorge Fontana, El Gran Chaco (1881, reprinted 1977), the diary (in Spanish) of an 18th-century explorer; and John Graham Kerr, A Naturalist in the Gran Chaco (1950, reprinted 1968), an account of the author's expeditions in 1889-97. More recent discussions can be found in the relevant sections of Herbert Wilhelmy and Wilhelm Rohmeder, Die La Plata Lnder: Argentinien, Paraguay, Uruguay (1963); and Preston E. James, Latin America, 4th ed. (1969); and in Philip Caraman, The Lost Paradise: An Account of the Jesuits in Paraguay, 1607-1768 (1975); and John Renshaw, "Property, Resources and Equality Among the Indians of the Paraguyan Chaco," Man, 23(2):334-352 (June 1988). Kempton E. Webb