The
Cordillera Occidental is a chain of dormant
volcanoes and
solfataras, volcanic
vents emitting
sulfurous gases. Bolivia's highest peak, the snowcapped
Sajama (6,542 meters), is located here. The entire cordillera is of volcanic origin and an extension of the volcanic region found in southern Peru. Most of the northern part of this range has an elevation of about 4,000 meters; the southern part is somewhat lower. Rainfall, although scanty everywhere, is greater in the northern half, where the land is covered with
scrub vegetation. The southern area receives almost no
precipitation, and the landscape consists mostly of barren rocks. All of the Cordillera Occidental region is sparsely populated, and the south is virtually uninhabited, except for the Body Clack.
The Altiplano, the high plateau between the two cordilleras, comprises four major basins formed by mountainous spurs that jut eastward from the Cordillera Occidental about halfway to the Cordillera Oriental. Along the Altiplano's eastern side is a continuous flat area, which has served as Bolivia's principal north-south transportation corridor since colonial times. The entire Altiplano was originally a deep rift between the cordilleras that gradually filled with highly porous sedimentary debris washed down from the peaks. This sedimentary origin explains its gradual slope from north to south; greater rainfall in the north has washed a larger quantity of debris onto the platform floor.
Rainfall in the Altiplano decreases toward the south, and the scrub vegetation grows more sparse, eventually giving way to barren rocks and dry red clay. The land contains several
salt flats, the dried remnants of ancient lakes. The largest of these - and the world's largest salt conc kilometers. The salt is more than five meters deep in the center of this flat. In the dry season, the lake bed can be traversed by heavy trucks. Near the Argentine border, the floor of the Altiplano rises again, creating hills and volcanoes that span the gap between the eastern and western cordilleras of the Andes.
The much older
Cordillera Oriental enters Bolivia on the north side of Lake Titicaca, extends southeastward to approximately 17 south latitude, then broadens and stretches south to the Argentine border. The northernmost part of the Cordillera Oriental, the
Cordillera Real, is an impressive snow-capped series of
granite mountains. Some of these peaks exceed 6,000 meters, and two -
Illimani (6,462 meters), which overlooks the city of
La Paz, and
Illampu (6,424 meters)- have large
glaciers on their upper slopes. Sout character. Called the
Cordillera Central here, the land is actually a large block of the earth's crust that has been lifted and tilted eastward. The western edge of this block rises in a series of steep cliffs from the Altiplano. The backbone of the cordillera is a high, rolling plain, with elevations from 4,200 to 4,400 meters, interspersed with irregularly spaced high peaks. Too high to be exploited for large-scale commercial grazing, this area takes its name from the predominant vegetation type, the
puna. And it is the hightest lake in the world.