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The Natural Environment

Natural Regions

Rising abruptly from the northwestern and western coasts of the continent are the Andes. They consist of a single chain in Venezuela, in the north, and through much of Chile and Argentina, in the south, but the central part of the mountain system consists of two or three parallel axes of mountains, known as cordilleras, or ranges. In southwestern Bolivia and southern Peru, a region of large intermontane plateaus called the Altiplano separates the ranges. In Peru and Argentina the ranges are separated by relatively narrow but deep valleys. Among the two dozen peaks that exceed an elevation of 17,000 ft (equivalent to 5,182 m) are a number of active volcanoes located in south central Chile, southern Peru and Bolivia, and Ecuador.

The vast uplands of Guiana, in the northeast, and of Brazil, in the east, have rolling to hilly surfaces, with broad plateaus and high mesas. The plateaus are higher and less broad in the highlands of Guiana. In the Brazilian Highlands, the greatest relief occurs in mountains that lie along the eastern coast, in many places rising abruptly from the sea. In general, the rocks of these uplands have weathered into infertile, reddish soils. Fertile soils derived from basaltic rocks are found in many valleys, however. To the south is the less elevated and relatively flat Patagonian Plateau. Although soils here are generally fertile, climatic constraints limit their agricultural usefulness.

The northernmost of the continent's principal lowland areas is the Orinoco Basin, which includes the Llanos—a region of alluvial plains and low mesas—and a vast system of valleys that converge toward the Amazon between the Caqueta and Madeira rivers. The Amazon Basin itself is a region of slightly rolling terrain. Farther south are the shallow valleys and flat plains of the Gran Chaco and the Pampas, both of which merge with the swampy floodplains of the Paraguay and Parana rivers.

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