PAMPAS, an extensive plain of Argentina, extending from the Rio Colorado north to the Gran Chaco, and from the foot-hills of the Andes east to the Parana and Atlantic coast. There are other pampas in South America, such as the pampas de Aullagas, in Bolivia, the pampas del Sacramento between the Huallaga and Ucayali rivers in eastern Peru, and others less well known, but when pampas is used alone the great Argentine plain is meant.
The Argentine pampas was once the bed of an ancient sea, covered on the west by shingle and sand, and on the east by deposits of estuary silt. Its western and northern limits, formed by the foot-hills of the Andes, and by the south of the great forested depression of the Gran Chaco, cannot be accurately de fined, but its area is estimated at 200,000 to 300,00o square miles. Its greatest breadth is across the south, between the 36th and 3 7th parallels, and its least in the north. It has a gradual slope from north-west to south-east, from an elevation above sea-level of 2,32o ft. at Mendoza to 20 ft. at Buenos Aires on the La Plata— the distance across being about 635 miles. Apart from a few sierras in the north-west and in the south, and a few longitudinal depressions in the west the plain appears perfectly level. The east, which is humid, fertile and grassy, has no natural arboreal growth, except in the vicinity of Cordoba and in the north, where algarrobas and some of the Chaco species are to be found. In the extreme south some species of low, thorny bushes cover consider able areas in the vicinity of the hill-ranges, otherwise the plain is destitute of native trees. Since the arrival of Europeans several species have been introduced successfully, such as the eucalyptus, poplar, peach, willow, ombli and others.
The distinctive vegetation of the grassy pampas is the tall, coarse-leaved "pampas grass" whose feathery spikes often reach a height of 8 or 9 feet. It covers large areas to the exclusion of all other species except the trefoils and herbs that grow between its tussocks. Since the advent of Europeans other forage plants have been introduced, the most successful being alfalfa (lucerne).
West of this region is a dry, sandy, semi-barren plain, called the "sterile pampas." It has large saline areas, brackish streams and lakes and immense sandy deserts, and in singular contrast to the fertile, treeless region of the east it supports large areas of stunted trees and thorny bushes. The grassy plains are well watered by streams flowing to the Parana, La Plata and coast, though some of these are brackish.
Civilized occupation is working many changes in the character and appearance of the pampas. The first change was in the intro duction of cattle and horses. Cattle were pastured on the open pampas and were guarded by men called gauchos, who became celebrated for their horsemanship, hardihood and lawlessness. At tention was then turned to sheep-breeding, which developed an other and better type of plainsmen. Then followed the extensive cultivation of cereals, forage crops, etc., which led to the general use of fences, the employment of immigrant labourers, largely Italian and Spanish, the building of railways and the growth of towns. The picturesque gaucho is disappearing in the eastern provinces, and the herds are being driven farther inland.