Argentina's Mountainous West: A Journey Through the Andes

The Mountainous West of Argentina

The Andes

The western region of Argentina is dominated by the Andes Mountains, one of the world's most significant mountain systems. The term "Andes" encompasses a vast array of high mountains and plateaus. The immense pressure exerted during the Andes' uplift affected older geological structures, dislocating and incorporating them into the mountain range. This process also impacted pre-existing formations like the foothills of La Rioja, San Juan, and Mendoza, as well as the Pampean Ranges.

Sub-Andean Sierras

The Sub-Andean Sierras are relatively young, low-lying mountains, reaching heights of around 2,500 meters above sea level. They stretch north to south, their peaks sharply eroded by rivers and heavy rainfall. Numerous rivers flow down from the Cordillera Oriental, converging into the Bermejo or Pasaje Juramento rivers. These rivers carve out narrow transverse valleys, connecting the northeast with the Chaco plain.

The earth's folded layers, known as anticlines, face inwards. Many of these elongated folds continue beneath the Chaco plain. These mountain ranges act as natural barriers against Atlantic winds, contributing to the rich vegetation on the eastern side. The area is also known for its mineral deposits (especially iron) and hydrocarbon reserves (oil and gas).

The Cordillera Oriental

East of the Puna, the Cordillera Oriental consists of two significant north-south mountain chains separated by ravines and valleys. The western chain is higher, reaching approximately 6,200 meters above sea level, with peaks capped by perpetual snow. The slopes are covered with "argayos," masses of rubble resulting from the extreme daily temperature fluctuations of the arid climate. Low summer rainfall triggers mudslides and rockfalls, accumulating at the base of the hills as alluvial fans.

Valleys formed by tectonic subsidence and filled with river sediments are also present. These broad, gently sloping valleys are home to major economic centers like San Salvador de Jujuy and Lerma. Another prominent feature is the streams, long, narrow valleys carved by rivers descending from the edge of the Puna, such as the Quebrada de Humahuaca (170 km long), Santa Maria (south of Guachipas), and the Quebrada del Toro.

The geological history of the Cordillera Oriental is visible in the vibrant colors and contrasts of the hillsides, like the "Seven Colors Hill" and the "Painter's Palette." These striking formations are the result of complex internal and external processes, including sedimentary layer shifts and rain erosion.

La Puna

An extension of Chile's Atacama Puna and the Bolivian Altiplano, La Puna is an ancient structure uplifted by Andean movements. Its landscape features a series of plateaus at altitudes of roughly 3,000 to 3,500 meters. Numerous volcanoes, mostly dormant, such as Socompa, Llullaillaco, and Sulphur, line the western edge.

The climate is heavily influenced by the relief. The eastern mountains and high ranges act as orographic barriers, blocking moisture from the west and creating the Puna's characteristic aridity. Low-flow rivers, fed by minimal rainfall and snowmelt, converge in the interior, forming salt flats and salt lakes. These formations result from dissolved salts (sodium chloride, borax) carried by the streams and accumulating in the valley bottoms. Examples include Salt Cauchari, Salinas Grandes, Laguna de Pozuelo, Salinas del Rincon, Salar de Pocitos or Chiron, and Salar de Hombre Muerto.

Human water consumption relies on rainwater or snowmelt collected in vegas, lowland wetland areas.