South America covers an area of 17870218 km2 and spans a broad latitudinal range, extending from 12° 28'N (Punta Gallinas, Colombia) to 55°59'S (Cabo de Hornos, Chile). Politically, the territory is divided into thirteen countries: Colombia, Venezuela, Guyana, Suriname, French Guiana, Brazil, Ecuador, Peru, Bolivia, Paraguay, Uruguay, Argentina, and Chile (Figure 1(a)). At a regional scale, four major geo-morphologic regions may be identified:
1. The Guaiana and Brazilian Highlands
2. The interior lowlands
3. The Cordillera
The Guiana and the Brazilian Highlands form the continental shield of north-eastern South America. This region contains the continent's oldest rocks, which are mostly covered by ancient sediments. The Guiana and
Brazilian Highlands are separated by the Amazon geosyncline.
A series of lowlands runs southward, along the middle part of the continent, from the Llanos del Norte, across the Amazonia and Gran Chaco, to the Argentinean Pampa. Despite the absence of major geographical barriers, the climate, hydrology, and vegetation patterns vary widely among these lowlands.
The Cordillera runs North-South along the Pacific shore. It is composed of the Andes ranges and high intermountain valleys and plateaus. The region is seismically active and frequently affected by earthquakes. Several volcanoes spread along the Andean cordillera, but most of them are inactive.
The Patagonian steppe lies east of the Andes and extends south from the Colorado River (35° S 69'W). Tablelands are typical features of the Patagonian landscape. They are made up of tectonically uplifted basaltic plateaus and coarse grain fans originated in the Andes (Figure 1).
As regards to the origin of lakes, at least seven different processes have played significant roles:
1. Tectonic activity
3. Glacial activity
4. Fuvial action
5. Aeolic action
6. Marine action
7. Human activity
These processes have acted either alone or in combination with others, and their importance differs among regions.
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