The morphology of Argentina reflects with great evidence the origin of the country, as it appears from the two maps on the geotectonic individualities, and on the structural lines, due to Keidel; it is easy to deduce from them the great morphological provinces which make up the Republic. The largest is the immense lowland that from the northern border (22 ° lat.S.) Descends to the 39 ° parallel S. approximately, limited to the west by the easternmost sierras and the Precordigliere, and to the east, first by the western edge of the Brasilia plateau, ancient penepiano raised, then from the Plata estuary and the Atlantic Ocean, towards which it widens. This large tectonic complex (sinking area or negative element) relatively homogeneous also under the lithological point of view,
a) Chaco, continuation of the Amazon, dense subtropical wood, furrowed by slow-flowing rivers and wandering among numerous marshes (esteros, bañados, etc.).
b) Mesopotamia Argentina (province of Corrientes and Entre Ríos) between Paraná and Uruguay, descending rich in waters from the Brazilian plateau; subtropical wood, but interrupted by large and frequent grassy clearings.
c) La Pampa in S. del Chaco, a boundless plain without trees or stones, the “sea of earth”, with vegetation of grasses, grasses and low bushes, which in turn is divided into: eastern or coastal (due to of the free navigation of the rivers of the Platense system, the provinces lapped by them are called coastal) richer in rainfall, and western or central, poor in rains, more arid, in which they are lost in temporary ponds (lagunas), or in salt marshes, rivers flowing down from the western highlands.
This maxim among the first-rate morphological units of Argentina also has, apart from the hardly penetrable Chaco, very high economic and therefore anthropogeographic value. Limited to the west by the ocean and the great navigable rivers, it is the most accessible part of the country, the first where conquest has firmly established itself, and where civilization has made the greatest and fastest progress. There the nation arose and the state found its fundamental nucleus.
The anthropogeographic value of the great Argentine plain has been revealed in such a singular way that it deserves to be remembered. In 1535 the adelantado D. Pedro de Mendoza founded on the right of the Plata the port of Santa María de los Buenos Aires, where the present city stands, but the colony could not sustain itself due to the hostility of the natives, the Querandíes, and to the great poverty of the country. After six years (1541) the settlers withdrew from the inhospitable district, taking refuge in the Asunción del Paraguay, and in the haste of boarding they abandoned some head of the cattle imported from Europe, especially horses. In that grassy plain, where, if small game swarmed, there were no tall herbivores at all, where the indigenous nomads themselves lived rather by fishing in the river than by hunting,
Along the western edge of the lowland rises the mountainous part of the republic, divided into its own Andes, and anteposed sierras, which according to their various origins, position and appearance have received from N. to S. the names of Subandine, of Pampeane (Pampinee) and Precordigliere. In the passage from the plain to the mountains, with the change of the lithological nature of the soil and the climatic conditions, the character of the vegetation changes: on the more uneven ground trees and tall bushes thicken, now more now less dense, with a predominance of xerophilous species. To the west, in general, this wooded covering, which bears the name of mountain, happens to the Chaco and the Pampa.
The Sierras Subandine limit the Chaco towards the west, from the Bolivian border to the province of Tucumán. Although they have a different origin and constitution from the Andes, they do not detach from it in a distinct and clear way, so to speak, they form the first rampart that, towards the Chaco, surrounds the very high and jagged eastern bastion of the Puna plateau. With this word, which means altitude sickness in the Inca language (Quechúa), we designate the extension within the borders of Argentina of the Bolivian plateau, a plateau of about 4000 meters high, between the two eastern and occmental branches of the Andes mountain range. In Argentina it includes the Puna de Atacama (governorate of los Andes), the Puna of Jujuy, and to a small extent also of Salta. Between the two main chains that surround it, with peaks above 6000 m. (Nevado de Chañi, 6100 m.) Run several parallel intermediate chains, separated by sandy plains, mostly desert, forming closed basins, in which during the rainy seasons the waters collect in vast brackish lagoons, which then evaporate in the rest of the year, they give rise to very extensive salty marshes and saline (salinas), often containing borates (calicas), undoubtedly due to the washout of the vast expanses of recent volcanic rocks and their tuffs (andesites, rhyolites, etc.) frequent on those plateaus. In the Puna, however, rainfall is very scarce (from 200 mm. To 0) and snowfalls are rare and not very extensive even on the highest peaks. The limit of perpetual snow passes in those places just below 6000 meters.
In S. di Tucumán, along the western edge of the Pampa, long rocky ridges emerge from the plain, initially low and sparse, but which become more frequent and higher with the approach of the Andes. They are the Sierre Pampeane, groups or bundles of parallel or subparallel cords, separated by intermediate plains, often without hydrographic outlet (bolsones) and therefore enclosing brackish and saline marshes; groups that although they have common composition and geological structure, to be detached from each other, lack an apparent orographic link, almost high mountainous islands rising from the general plan. The rich bundle of sierras of Catamarca and Rioja belong to it, in which the latter stand out the Sierra of Famatina with peaks of 6200 m., The great Sierra of Córdoba, the Sierra of San Luis, and the westernmost ones of the province of San Juan.
Although, due to their isolation, they are part of themselves, the sierras of the province of Buenos Aires fall within the morphological type of the pampeane.
The Argentine side of the imposing Andes chain, with the supreme peaks of the system, the Mercedario (6670 m.), Aconcagua (6960?) and Tupungato (6550), subdivided, solely for reasons of geological structure, into its own Cordillera, of Mesozoic rocks, on which the political border towards Chile runs, and Precordillera, of Paleozoic rocks and crystalline, separated from the Sierre Pampeane by a wide groove (see andes).
To S. del Colorado, the southern limit of the Pampa, is succeeded by the region of the Patagonian plateaus, with a steppe character in terms of vegetation. Opposite of the Argentine lowland. Patagonia is an uplifted area, in which the type of plateau (meseta) that is sometimes elevated up to 1000 m prevails. on the sea. The rivers, descending from the Patagonian Andes to the sea, cross it, carving large and deep valleys, flanked by steep terraces of erosion, which connect with those of the Atlantic coast (barrancas). All the rather heterogeneous geological formations that make up Patagonia have been reduced to the common type of plateau, both because the oldest were already reduced to penepian planes by abrasion, and because the most recent (tertiary) have still remained undisturbed by time from their deposition.
Between the western edge of the plateaus and the Patagonian Andes lies the region of fiord-like lakes or alpine lakes, most of which are of glacial origin. Many, like one of the largest, the Nahuel Huapí send the waters to the Atlantic; but a certain number instead, such as Buenos Aires, have an outlet towards the Pacific thanks to captations in favor of the very rainy Chilean side, some of which also occurred very recently. For Argentina 2018, please check ethnicityology.com.
Remarkable singularity of the Patagonian plateaus are some lake basins excavated in them, completely independent from the current hydrography, and despite the considerable depth completely drained by the very dry and windy climate. Such are, in the territory of the Neuquén, the Cuenca de Vidal used by the engineer Cipolletti as a diversion to welcome the impetuous and sudden floods of the Neuquén for the benefit of the irrigation of the Río Negro valley, and further to the N., always in the Neuquén, the much greater Cuenca de Añelo, whose bottom is 140 m. lower than the nearby Neuquén valley. The Bajo (lower) de Gualichú in S. del Río Negro, and the Bajo de San Julián, much more southern, should still be remembered.
The Patagonian Andes, which are the second morphological element of Patagonia, differ from the Argentine in composition and geological structure not only, but also from the point of view of the configuration of the soil, because they are more broken and dismembered by deep valleys, due to their incomparably greater intensity. so with rains, as with the Quaternary glacial phenomenon. Another element that is not found further north, namely a vast basaltic platform (see southern andes), also participates in the structure of the Patagonian Andes. Here the vegetation cover is favored by the abundance of rainfall, and there is the mountain forest based on beech trees (Nothofagus).
The small territory of Misiones, morphologically not distinct from Argentine Mesopotamia, differs from it in its geological constitution, being the only strip of Brasilia that is part of the Argentine territory. It consists of red triasic sandstones, in which an imposing basaltic flow is interspersed whose precipitous edge gives rise to the grandiose and beautiful Iguazu waterfall.
Although the oceanic coast from the Plata estuary to Tierra del Fuego has quite a few gulfs and indentations, it has no general relationship with the geological structure of the country. Cape Corrientes itself, where the Sierra del Tandil approaches the coast, is not a pronounced coastal overhang, but just corresponds to a very obtuse aspect of the coastal line. In the province of Buenos Aires, up to the mouth of the Colorado, the Pampa reaches the sea, ending there with a 30-40 m escarpment. of maximum height, usually separated from the oceanic waters by a more or less wide stretch of sandy beach, run by the tidal waves. There is only one important inlet: Bahía Blanca, home to a very active commercial port of cereals and wool, joined to a military port, built by the Italian ing. Luiggi.
Beyond the mouth of the Colorado and the Río Negro begins the Patagonian coast, a high and steep edge of the interior plateaus, broken here and there by the outlets of rivers, and, although rich in gulfs and protrusions, such as the peninsula of Valdez, in the highest degree inhospitable and importunate. This impervious nature left the interior of Patagonia unknown for a long time, revealed only from 1880 onwards by the numerous expeditions of discovery by land.