The Andes constitute Argentina's western boundary with Chile from Latitude 22°50^prime South to Latitude 50°48^prime South. The mountain belt of western Argentina consists of a series of sub-parallel meridional chains, which decrease in number, width, and elevation from north to south. Although the Andes may be considered as a single geographic unit, they are formed by several different morpho-structural elements oriented from north-northwest to south-southeast, and therefore oblique to the trend of the continental divide.

The various morpho-structural elements which, from north to south, constitute the Chilean-Argentinian Andes, are as follows: (1) the high plateau of the Puna de Atacama, followed toward the east by the Eastern Cordilleras (Prepuna) and the Subandean ranges, (2) the Pampean ranges, (3) the Precordillera of La Rioja, San Juan, and Mendoza, (4) the Cordillera Frontal, (5) the Cordillera Principal, and (6) the Patagonian Cordillera.

The extension and main stratigraphical and structural features of the different morpho-structural elements, as well as the geologic evolution of western Argentina, are summarily described.

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