Andes

THE ANDES IS A mountain system in South America. The mountains form the “backbone” of South America, stretching from the Caribbean coast along the western side of the continent to its southern tip. The name Andes probably derives from either Quechua or Aymara, the two principal Native American languages of South America. Plate-tectonic forces during the Cenozoic Era created the Andes. The mountains are a result of a collision between the continental South American plate and the oceanic Nazca plate that created high peaks and steep slopes. The region is still tectonically active, as earthquakes are common and there are frequent volcanic eruptions. The Andes sometimes serve as a geographic boundary that divides countries, as is the case of the border between ARGENTINA and CHILE. The mountains also divide regions within individual countries.

The highest peaks are found in Argentina, PERU, and ECUADOR. ACONCAGUA MOUNTAIN in Argentina is the highest peak in the Western Hemisphere at 22,834 ft (6,960 m). The lowest peaks are found in the southern and northern extremes. The Andes are widest in BOLIVIA, where there are actually two distinct ranges known as the Cordillera Occidental (Western Range) and Cordillera Oriental (Eastern Range).

Much of the Andes lies in the tropics. However, altitude is generally more of a determining factor than latitude. Indeed, there are even glaciers and snow near the equator. Climate and vegetation are also determined by altitude. Furthermore, elevation affects temperatures, even at the same latitude. Temperatures tend to decrease about 3.7 degrees F for every 1,000-foot (305 m) increase in altitude. For example, Quito, Ecuador, located high in the Andes, has an average annual temperature of 54.6 degrees F (12.5 degrees C). Guayaquil, Ecuador, located at almost the same latitude, but on the coast, has an average temperature of 78.2 degrees F (25.6 degrees C).

In the tropics, different elevations are divided into several distinct categories. Altitudes up to about 3,000 ft (914 m) are referred to as tierra caliente (hot country). Elevations located between 3,000 and 6,000 ft (914 m and 1,829 m) are called tierra templada (temperate land). Tierra fria (cold land) can be found at altitudes of 6,000 to 12,000 ft (1,829 m to 3,657 m). Finally, regions above 12,000 ft (3,657 m) are classified as tierra helada (frozen land).

Much of the Andean region is arid, including the Atacama Desert. On the western side of the Andes, streams do not have well-defined headwaters. In contrast, on the eastern side, there is more rain and more significant headwaters. Two of South America’s major river systems—the AMAZON and the Orinoco—both begin in the Andes.