A cordillera is an extensive chain of mountains or mountain ranges. The term derives from the Spanish cordilla, a diminutive of cuerda, or "cord". It is most commonly used in the field of physical geography.The term is particularly applied to the various ranges of the Andes of South America, and less frequently to other mountain ranges in the "ridge," which rims the Pacific Ocean. In Colombia and Venezuela the cordilleras are named according to their position: Cordillera Occidental, Central, and Oriental. Various local names are in use in Ecuador, Peru, Bolivia, Chile, and Argentina.The structure of mountains of this type is complex, usually the result of folding and faulting accompanied by volcanic activity. In South America the ranges are surmounted by numerous volcanic peaks. Argentina's Mt. Aconcagua, at 22,834 feet (6,960 meters) high, is the highest point in the Western Hemisphere. A number of these volcanoes have been active in historic times. Aside from the volcanic peaks, the crests include many narrow ridges, some of which reach into the zone of permanent snow. Between the ranges there are numerous inhabited valleys, basins, and low plateaux with a wide range of elevations.