22. Peneplain Cut by Canyons, Andean Slopes, Peru
Much of the Central Andes is occupied by a 3000–4000-meter-high (9800–13,120 feet) plateau (the altiplano) that has been rapidly uplifted during the last 20 million years. Rapid uplift implies rapid downcutting by rivers, and the photograph reveals spectacularly the extent to which this has operated on the western slopes of the plateau. The photograph shows the great canyon of the Rio Ocona (left) and its tributary canyon, the Cotahuasi. Both canyons are nearly 3000 meters (9800 feet) deep at their deepest, and thus are much deeper than the Grand Canyon. The Grand Canyon is more impressive on the ground, however, because it is much narrower, and its walls are much steeper.
Erosion has nibbled its way almost to the foot of the large snow-capped mountain at the center, the 6117-meter (20,000 feet) Nevado Solimana. This mountain and the larger Nevado Corupuna (6377 meters or 20,916 feet) in the lower right corner are both dissected andesite volcanos. The peneplain on which the volcanos are constructed and that is being dissected is covered by volcanic units that offer the possibility of dating the stages in the uplift of the Andes.
STS-41D, August-September 1984. Picture #14-34-005.