In the deep south of Chile and Argentina, the mountains rise in some of the wildest regions of the world, Patagonia and Tierra del Fuego. In Argentina, Aconcagua (22,835 ft.) is the highest point in South America, and the highest in the entire Western Hemisphere. In the northern Andes, the majority of inhabitants live above 9,000 feet. The capital cities of Bolivia (La Paz), Ecuador (Quito) and Colombia (Bogotá) are all high altitude cities. La Paz is the highest capital city in the world (11,910 ft.). In the south, the Andes are too cold for habitation above 5,000 to 8,000 feet. 

The Andes are generally folded mountains, composed of limestone, sandstone, slate, and some granite. Large amounts of lava also enter the mix as the Andes are home to numerous volcanoes, some active. Frequent earthquakes provide further evidence of the dynamic nature of the region's geology.