The Bolivian Andes is composed primarily of two ranges or cordilleras. The Cordillera Occidental is characterized by volcanic activity. The much older Cordillera Oriental, also known as the "Cordillera Real," is an impressive snow-capped series of granite mountains.
In western Bolivia, the Cordillera Occidental is characterized by volcanic activity, making up the natural border with Chile. It begins near the border with Peru at the Juqhuri massif and ends in the south at the Licancabur volcano, which is at the southern limit of Bolivia with Chile.
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.
Topographic map of Bolivia showing (east to west) plains of the Amazon Basin in green, Sub-Andean Zone in red, Eastern Cordillera in white, Altiplano in gray, and Western Cordillera in white
The Cordillera Occidental, the western range of the Bolivian Andes, is essentially a chain of dormant volcanoes and solfataras, which are volcanic vents that emit sulfurous gases. Bolivia's highest peak, the snowcapped Nevado Sajama at 6,542 m (21,463 ft) asl, is located in this range.
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 m (13,000 ft); the southern part is somewhat lower.
Rainfall, although scanty everywhere, is more significant in the northern half, where the land is covered with scrub vegetation. The southern area receives almost no precipitation, and the landscape consists mainly of barren rocks.
The climate of the Cordillera Occidental is cold and inadequate for animal and plant life. The regions are sparsely populated, and the south is virtually uninhabited.
The range consists of three sections:
The northern section contains the highest peaks in Bolivia, the tallest of which is the volcano Sajama at 6,542 m (21,463 ft). It is perennially covered in snow. In addition, it contains the volcanoes Pomerape and Parinacota.
The central section is situated between Uyuni and Coipasa. Its most prominent summit is the Ollagüe (Ullawi) volcano on the border with Chile.
The southern section, characterized by volcanic activity, sandstorms, and fog, contains the 5,920 m (19,422 ft) Licancabur volcano, which is on the southern limit of Bolivia with Chile. Laguna Colorada and Laguna Verde can be found near Licancabur, so named because of their respective colors.
The Altiplano, the high plateau between this range and the Cordillera Oriental, comprises four major basins formed by mountainous spurs. The spurs jut eastward from the Cordillera Occidental about halfway to the Cordillera Oriental.
Cordillera Oriental: "Cordillera Real" and "Cordillera Central"
The Cordillera Oriental is the easternmost of the Bolivian Andes cordilleras. It extends generally north-south for about 1,200 km (750 mi) through the length of the country.
The northernmost part of the Cordillera Oriental, known as the "Cordillera Real," is an impressive snow-capped series of granite mountains. Some of these peaks exceed 6,000 m (19,685 ft), and two - Illimani 6,424 m (21,076 ft), which overlooks the city of La Paz and Illampu 6,424 m (21,076 ft) - have large glaciers on their upper slopes.
The northeastern flank of the Cordillera Real is known as the Yungas. The steep, almost inaccessible slopes and peaks of this mainly semitropical valley area northeast of La Paz offer some of the most spectacular scenery in Bolivia.
Rainfall is heavy, and lush vegetation clings to the sides of narrow river valleys. The land is among Bolivia's most fertile, but poor transport has hindered its agricultural development. The government attempted to build a railway through the Yungas in 1917 to connect La Paz with the eastern lowlands. The railway was abandoned, however, after completion of only 150 km (93 mi).
South of 17 south latitude, the range changes character. Called the "Cordillera Central" here, the land is 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 cliffs from the Altiplano. The backbone of the cordillera is a high, rolling plain with elevations from 4,200 m (13,780 ft) to 4,400 m (14,436 ft), 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.
The eastern slopes of the Cordillera Central descend gradually in a series of complex north-south ranges and hills. Rivers draining to the east have cut long narrow valleys; these valleys and the basins between the ranges are favorable areas for crops and settlement.
Rich alluvial soils fill the low areas, but erosion has followed vegetation removal in some places. The valley floors range from 2,000 - 3,000 m (6,560 - 9,843 ft) above sea level. This lower elevation means milder temperatures than those of the Altiplano.
The cities of Sucre, Cochabamba and the upper area of the Tarija department are located in the basins of this vast region.