TOPOGRAPHY. The surface is diversified by the Andean Cordilleras on the western border, and by the interior highlands; but the greater part of the area is a flat plain sloping gently toward the Atlantic Ocean. The Andes system in the northwest is a broad plateau, broken into parallel or slightly diverging ridges, whieh reach well to the east of the Chilean frontier, and occupy large areas in the Provinces, of Jujuy, Salta, Tucuman, Catamarca, Rioja, and San Juan. Above the plateau rise numerous crests to a height of over 17,000 feet, attaining extreme elevations in Aconcagua (22,860), Mereedario (22,315), Eamatina (about 20,700), and Tupan gato (20,286). In the western Province of Men doza, the Andes eontraet laterally, and gradually fall off in height toward the south, where they end in the highlands of Tierra del Fuego. East of the Cordilleras, the most notable elevations are the north and south ridge of the Sierra de Cordoba, on the western boundary of the Province of Cordoba; the 'Pandit and Ventana Highlands,in the Province of Buenos Ayres; and the continua tion of the mountain range of Lower Brazil. in the Territory of Misiones. These independent moun tain ranges, however, are of no great areal or topographic importance: the entire region east ward from the base of the Andean Plateau is generally fiat, or slightly and falls gradually from an elevation of about 2000 feet to, or nearly to, the level of the sea. That part
of the plain north of the Rio Salado (affluent of the Parana) is called the "Gran Chaco" (great hunting-ground), and contains extensive forests. Between the Rio Salado and the Rio Negro, in central Argentina, are the characteristic pampas, monotonous stretches of level ground covered with grass during the wet season. Northward the pampas graduate into more forested country, and are also marked by a large interior drainage system and by saline swamps, while to the south they merge into the higher plains or steppes of Patagonia, which are disposed at an elevation ranging from 2000 feet at the base of the Andes to 500 feet or less on the coast. Be tween the Rio Parana and the Rio Uruguay are toe Provinces of Corrientes and Entre Rios,which are generally low, the latter Province, however, containing a small area of hills in the west.