GEOGRAPHY: Natural Regions

Structurally and climatically, Bolivia consists of two main regions: the highlands and the eastern lowlands, divided between the Amazon and Parana basins.

The Andes

The highlands of Bolivia consists of three distinct parts: the Cordillera Occidental; the Altiplano; and the Cordillera Oriental. The Cordillera Occidental is part of the Andean range that extends along the western fringe of South America. It features many active volcanoes, part of a line of volcanoes that runs from southwest Peru to Chile. There is a distinct climatic difference between the northern and southern parts of the Cordillera Occidental; the latter are arid and almost inhabited. In the north, some high valleys, with altitudes of up to 14,000 feet, are inhabited by Indians who engage in subsistence agriculture (mostly irrigated) and pastoralism. With peaks of more than 20,000 feet, steep slopes, and much volcanic activity, the Cordillera Occidental is the least inhabited part of Bolivian Highlands.

The Altiplano is a high plateau, 12,000-13,000 feet above sea level, which lies between the Occidental and Oriental ranges. It broadest point is over 200 miles north Lake Poopo, where the Andes reach their greatest width, approximately 400 miles. The Altiplano is divided into a number of basins by spurs of the Andes. The northernmost of these basins, which extends into Peru, is partly occupied by the Lake Titicaca, at 12,507 feet, the world's highest large.

The Capital La Paz, the highest (11,900 feet) large city in the world, is situated in a valley southeast of Lake Titicaca below the rim of the Altiplano. Part of the population of the Altiplano has since before the arrival of the Europeans been engaged in mining activities concentrated around two main centers: Corocoro and Oruro. These areas were important soucees of silver in the Spanish colonial period.

The structure of the Cordillera Oriental is more varied and complex, with distinctly different landscapes and habitats in the northeast, which follows a northwest to southeast direction, and the south, which follows a north to south direction. The northeastern part rises abruptly to great heights above the Altiplano (the Titicaca basin and La Paz Valley) and has snow-capped peaks of over 21,000 feet. The eastern slopes are densily covered by forest and are known as the Yungas, the wettest part of the Bolivian Andes.

The southern part (from the vecinity of Santa Cruz) rises abruptly from the Altiplano is a precipitous escarpment but has a less rigged upper surface that slopes gently toward the eastern lowlands. This high level surface of 12,000-14,000 feet is surmounted by a number of short ranges with higher peaks. Known as the Puna, this moderatly high surface relief a number of rivers that drain parts of the Altiplano and the Cordillera Oriental into the Paraguay river and the Parana basin. Natural conditions in the basins and valleys of the Cordillera Oriental are much more favorable to human settlement than those of the Cordillera Occidental and the Altiplano.

The eastern lowlands

In the eastern lowlands, there are distinct differences between the natural features of the northeast and those of the southeast. In the northeast the Llanos de Mamore, which slopes gently to the Amazon Basin, is well watered by rain and rivers and has rich natural vegetation, while the southeast the Gran Chaco, which slopes toward the Pilcomayo and Paraguay rivers, is semiarid, with dry scrub and savanna and occasional gallery forests along the rivers. The eastern lowlands are sparsely populated. The discovery of oil and natural gas, the development of roads between Santa Cruz (the region's main urban center) and the urban centers of the Altiplano, and government-backed settlement have resulted in a significant increase in population in this region since 1950s. The eastern lowlands are Bolivia's main source of tropical agricultural products.

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