RELIEF FORMS OF THE CONTINENTS. AT

 

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Fig, 44, Orographic Chart of South America,
(Light portions, mountains; shaded portions, plains.)
1, System,of the Andes; 2, Plateau of Quito; 3, Plateau of Bolivia;

4, Aconcagua; 5, Plateau of Guiana; 6, Plateau of Brazil; 7, The
Orinoco; 8, The Amazon; 9, The La Platte,
Il. SOUTH AMERICA.

116, Surface Structure. — The Predominant
Mountain-System of South America is in the west.

The Secondary Systems are in the east.

The Great Low Plain lies between them.

117, The System of the Andes, which extends
along the western border of the continent, is the

_“predominant mountain-system. It is composed
mainly of two approximately parallel chains
_ separated by wide and comparatively level val-
leys. On the north there are three chains, and
‘onthe south but one; in the centre, mainly two.
The chains are connected by transverse ridges,
forming numerous mountain-knots.

The Andes System forms a continuation of
the Pacific Mountain-System. A wide depression
at the Isthmus of Panama marks their separation.
From this point the Andes increase in height
toward the south, probably reaching their high-
est point in Chili, where the volcanic peak of
Aconcagua, 28,910 feet, is believed to be the cul-
minating point of South America, and of the West-
ern Continent.

Nevada de Sorata was formerly believed to be the cul-
minating point of South America, but recent recalculations

 

 

of the observations have resulted in a loss of nearly 4000
feet of the supposed height of Sorata. Some authorities
still claim that several peaks in Bolivia reach an ele-
vation of nearly 25,000 feet.

The Andes Mountain-System terminates ab-
ruptly in the precipitous elevations of Cape Horn.

Numerous table-lands are included between the parallel
ranges: the most important are—the plateau of Quito, 9543
feet; the plateau of Pasco, in North Peru, 11,000 feet; the
plateau of Bolivia, from 12,000 to 14,000 feet. From most
of these higher plateaus volcanic peaks arise.

118. The Secondary Mountain-Systems of South
America are the plateaus of Brazil and Guiana.
They both lie on the eastern border.

The Plateau of Brazil is a table-land whose
average height is about 2500 feet. Narrow
chains or ridges separate the river-valleys.

The plateau of Brazil forms the watershed between the
tributaries of the Amazon and the La Plata. Along the
Atlantic a moderately continuous range descends in steep
terraces to the ocean. The average altitude is more than
double that of the western portion of the plateau. The
highest peaks are somewhat over 8000 feet.

The Plateau of Guiana, smaller than the Plateau
of Brazil, but about equally elevated, forms the
watershed between the Orinoco and the Amazon.

 

Fig. 45, Amazon River Scenery.

119. The Great Low Plain of South America
lies between the predominant and the secondary
mountain-systems. It is mainly of alluvial origin,
but slightly elevated, and is much more level than
the great plain of North America.

This plain is drained by the three principal river-sys-