South of the Bermejo the land is more elevated and drier, though large depressions covered with marshy lagoons are to be found, similar to those farther north.
The largest of the rivers through which Argentina drains into the Plata system are the Pilcomayo, which rises in Bolivia and flows south-east along the Argentine frontier for about 400 m.; the Bermejo, which rises on the northern frontier and flows south-east into the Paraguay; and the Salado del Norte (called Rio del Juramento in its upper course), which rises on the high mountain slopes of western Salta and flows south-east into the Parana.
None of the tributaries of the La Plata system thus far mentioned is navigable except the lower Pilcomayo and Bermejo for a few miles.
The territories of the Gran Chaco, however, are covered with a characteristic tropical vegetation, in which the palm predominates, but intermingled south of the Bermejo with heavy growths of algarrobo, quebracho-colorado, urunday (Astronium fraxinifolium), lapacho (Tecoma curialis) and palosanto (Guayacum officinalis), all esteemed for hardness and fineness of grain.
Other palms abound, such as the pinch!) (Cocos australis), mbocaya (Cocos sclerocarpa) and the yatai (Cocos yatai), but the predominating species north of the Bermejo is the caranday or Brazilian wax-palm (Copernicia cerifera), which has varied uses.
Then came the hopeless revolts of the Indians against intolerable oppression, the abortive rebellions of Hernandez de Contreras and John Bermejo (Bermudez) against the mother country (1550), the foundation of Leon, future rival of Granada, in 1610, its sack by the buccaneers under William Dampier in 1685, and, lastly, the declaration of independence (1821), not definitively acknowledged by Spain till 1850.
The Bermejo, which is an Argentine river, receives one large tributary from the Bolivian uplands, the Tarija or Rio Grande, which drains a small district south-east of the Santa Victoria sierra.
The western part of the province is drained by the Bermejo, which flows southward into the closed lacustrine basin of Mendoza.
The gaps of Bermejo and Iglesia, in the Uspallata road, the best known of all the passes between Argentina and Chile, are at 13,025 ft.