of Bolivia is comprised within the Andean cordilleras which cross
its south-west corner and project east toward the Brazilian highlands
in the form of a great obtuse angle. The cordilleras, divided
into two great parallel chains, with flanking ranges and spurs to
the east, reach their greatest breadth at this point and form
the massif of the Andean system. It is made up of a number
of parallel ranges enclosing great elevated plateaus broken by
transverse ranges and deep ravines. North-east of Lake Titicaca
there is a confused mass or knot (the Nudo de Apolobamba)
of lofty intersecting ridges which include some of the highest
peaks in South America. Below this mountainous area the
ranges open out and enclose extensive plateaus. The western
range, the Cordillera Occidental, a part of the boundary between
Bolivia and the northern provinces of Chile, closely follows the
coast outline and forms the western rampart of the great Bolivian
tableland or alta-planicie, which extends from the Vilcanota
knot in Peru, south to the Serrania de Lipez on the Argentine
frontier, is 500 m. long, and about 80 m. broad, and contains
about 40,000 sq. m. The northern part of this plateau is commonly
called the puna; the southern part, the “desert of
Lipez,” in character and appearance is part of the great Puna
de Atacama. This plateau has an average elevation of about
12,650 ft. near Lake Titicaca, but descends about 1000 ft. toward
its southern extremity. It is a great lacustrine basin where once
existed an inland sea having an outlet to the east through the
La Paz gorge. The plateau is bleak and inhospitable in the
north, barren and arid toward the south, containing great saline
depressions covered with water in the rainy season, and broken
by ridges and peaks, the highest being the Cerro de Tahua,
17,454 ft. Overlooking the plateau from the west are the snow-clad
peaks of Pomarape (20,505 ft.), Parinacota (20,918 ft.),
Sajama (21,047), Huallatiri (21,654), Lirima (19,128), and the
three volcanic peaks, Oyahua (19,226), San Pedro y Pablo
(19,423) and Licancaur (19,685). The eastern rampart of this
great plateau is formed by the Cordillera Oriental, which extends
north-west into Peru under the name of Carabaya, and
south to the frontier in broken ranges, one of which trends south-east
in the vicinity of Sucré. The main part of this great range,
known as the Cordillera Real, and one of the most imposing
mountain masses of the world, extends from the Peruvian border
south-east to the 18th parallel and exhibits a series of snow-crowned
peaks, notably the triple-crested Illampu or Sorata
(21,490 ft.), Illimani (Conway, 21,204), Cacaaca (20,571) and
Chachacomani (21,434). Of the ranges extending south from
the Cordillera Real and branching out between the 18th and 19th
parallels, the more prominent are the Frailes which forms the
eastern rampart of the great central plateau and which is celebrated
for its mineral deposits, the Chichas which runs south from
the vicinity of Potosi to the Argentine frontier, and the Livichuco
which turns south-east and forms the watershed between the
Cachimayo and Pilcomayo. The more prominent peaks in and
between these ranges are the Asanaque (16,857), Michaga
(17,389), Cuzco (17,930), Potosi (15,381), Chorolque (18,480)
and Tuluma (15,584). At the southern extremity of the great
plateau is the transverse Serrania de Lipez, the culminating
crest of which stands 16,404 ft. above sea-level. The eastern
rampart of the Bolivian highlands comprises two distinct
chains—the Sierra de Cochabamba on the north-east and the
Sierra de Misiones on the east. Between these and the Cordillera
Oriental is an apparently confused mass of broken, intersecting
ranges, which on closer examination are found to conform more
or less closely to the two outside ranges. These have been
deeply cut by rivers, especially on the north-east, where the rainfall
is heavier. The region enclosed by these ranges is extremely
rugged in character, but it is esteemed highly for its fertile
valleys and its fine climate, and is called the “Bolivian Switzerland.”
Lying wholly within the tropics, these mountain masses
form one of the most interesting as well as one of the most
imposing and difficult regions of the world. At their feet and in
their lower valleys the heat is intense and the vegetation is
tropical. Above these are cool, temperate slopes and valleys,
and high above these, bleak, wind-swept passes and snow-clad
peaks. West of the Cordillera Oriental, where special conditions
prevail, a great desert plateau stretches entirely across one corner
of the republic. Apart from the Andean system there is a group
of low, broken, gneiss ranges stretching along the east side of
Bolivia among the upper affluents of the Mamoré and Guaporé,
which appear to belong to the older Brazilian orographic system,
from which they have been separated by the erosive action of
water. They are known as the Sierras de Chiquitos, and are
geologically interesting because of their proximity to the eastern
projection of the Andes. Their culminating point is Cerro
Cochii, 3894 ft. above sea-level, but for the most part they are
but little more than ranges of low wooded hills, having in general
a north-west and south-east direction between the 15th and 19th
parallels.
The popular conception of Bolivia is that of an extremely rugged mountainous country, although fully three-fifths of it, including the Chiquitos region, is composed of low alluvial plains, great swamps and flooded bottomlands, and gently undulating forest regions. In the extreme south are the Bolivian Chaco and the llanos (open grassy plains) of Manzo, while above these in eastern Chuquisaca and southern Santa Cruz are extensive swamps and low-lying plains, subject to periodical inundations and of little value for agricultural and pastoral purposes. There are considerable areas in this part of Bolivia, however, which lie above the floods and afford rich grazing lands. The great drawback to this region is defective drainage; the streams have too sluggish a current to carry off the water in the rainy season. Between the Chiquitos sierras and the Andes are the Llanos de Chiquitos, which have a higher general elevation and a more diversified surface. North of this elevation, which formed the southern shore of the ancient Mojos Lake, are the llanos of Guarayos and Mojos, occupying an extensive region traversed by the Guaporé, San Miguel, Guapay, Mamoré, Yacuma, Beni and Madre de Dios rivers and their numerous tributaries. It was once covered by the great Mojos Lake, and still contains large undrained areas, like that of Lake Rojoagua (or Roguaguado). It contains rich agricultural districts and extensive open plains where cattle-raising has been successfully followed since the days of the Jesuit missions in that region. The lower slopes of the Andes, especially toward the north-west, where the country is traversed by the Beni and Madre de Dios, are covered with heavy forests. This is one of the richest districts of Bolivia and is capable of sustaining a large population.
The river-systems of Bolivia fall naturally into three distinct regions—the Amazon, La Plata and Central Plateau. The first includes the rivers flowing directly and indirectly into the Madeira, one of the great tributaries of the Amazon, together with some small tributaries of the Acré and Purús in the north, all of which form a drainage basin covering more than one-half of the republic. The two principal rivers of this system are the Mamoré and Beni, which unite in lat. 10° 20′ S. to form the Madeira. The Mamoré, the upper part of which is called the Chimoré, rises on the north-east slopes of the Sierra de Cochabamba a little south of the 17th parallel, and follows a northerly serpentine course to its confluence with the Beni, the greater part of which course is between the 65th and 66th meridians. The river has a length of about 600 m., fully three-fourths of which, from Chimoré (925 ft. above sea level) to the rapids near its mouth, passes across a level plain and is navigable. The principal Bolivian tributary of the Mamoré, the Guapay or Grande, which is larger and longer than the former above their confluence and should be considered the main stream, rises in the Cordillera Oriental east of Lake Pampa Aullaguas, and flows east to the north extremity of the Sierra de Misiones, where it emerges upon the Bolivian lowlands. Turning to the north in a magnificent curve, it passes around the south-east extremity of the Sierra de Cochabamba, skirts the Llanos de Chiquitos, and, turning to the north-west, unites with the Mamoré at Junta de los Rios in about 15° 20′ S. lat. and 64° 40′ W. long. It has a tortuous course of over 700 m., which is described as not navigable. The principal tributaries of the Guapay are the Mizque, Piray or Sará and Yapacani, the last rising on the east slopes of the
