Andes Mountains

The Andes run for roughly 8,900 kilometres along the western edge of South America, from the southern end of the continent to its northern Caribbean coast. They are not a single ridge: the system consists of multiple parallel and transverse cordilleras, high plateaus and intervening basins. A commonly used regional division distinguishes the Southern, Central and Northern Andes, although geographers do not agree on a single set of boundaries. In the central part of the range, the Altiplano is a high interior plateau between major mountain chains. Aconcagua, on the Argentina–Chile border, is the highest summit, rising about 6,959 metres above sea level.

The Andes are an active example of mountain building at a convergent plate boundary. The oceanic Nazca Plate moves toward and descends beneath the continental South American Plate. Compression and deformation of the overriding crust have helped uplift the mountain chain, while melting above the descending plate feeds a volcanic arc along much of the western margin. The continuing tectonic boundary produces earthquakes as well as volcanoes; its geological behaviour varies along the length of the range. The Andes therefore form part of the active Pacific margin of South America, rather than a set of mountains shaped only by ancient, completed processes.

The Andes cross a wide range of latitudes and elevations, so climate and vegetation change markedly from one region and slope to another. High elevations include cold grasslands, snow and glaciers, while lower slopes in the tropics include forests. In the tropical Andes, steep environmental gradients and isolated habitats support unusually rich biodiversity and many species found nowhere else. Mountain catchments also feed large river systems: the Tropical Andes are an important water source for the main stems of the Amazon and Orinoco. These connections make the range significant well beyond its peaks, linking highland ecosystems to downstream communities and lowland habitats.

People have built communities and ways of life across the Andes’ varied elevations and climates. The Tropical Andes biodiversity hotspot alone is home to more than 40 Indigenous groups, whose communities have important roles in land use and regional life. Agriculture, settlements, transport routes and resource use all interact with steep terrain and sensitive ecosystems. The Historic Sanctuary of Machu Picchu in Peru illustrates one such relationship: UNESCO describes an Inca cultural landscape in the eastern Andes where architecture, terraces, trails and the surrounding mountain environment are closely connected. It is one landmark within a much larger and culturally diverse mountain region.