Relevo do Brasil

Resumo

The author, professor Affonso VARZEA, of the Institute of Education of the Federal District, deals in this article with the relief of Brazil in its general lines.

            To start with he lays stress upon the necessity of national geography being interpreted and appraised in accordance with the modern methodology of geographic science, in order to create a reaction against the ancient exaggeration of nomenclature such as occurs, for instance, as regards mountains and chains, when, in fact, Brazil is "a country of old plateau, hemmed in between a long and really narrow seaboard plain bathed by the Atlantic, and the valleys of the Orenoco, Amazon, Paraná-Paraguai and Uruguai rivers ... ".

            The author confines and gives the general features of prominence of the two old plateaux, the Brazilian and that of the Guyanne, geologically identifying them. The plateau of the Guyanne, though with highest altitudes equal to those of the Brazilian highlands, has steeper inclines (in the Northern watersheds) due to its smaller area. As to the great Brazilian plateau, its steepest borders are those which fringe the ocean, while it gradually becomes lower towards the North and the West.

            Studying in greater detail the principal parts of the Brazilian plateau, the author describes "the country of the mountain ranges", that is its Eastern ridges formed by the complex architecture of archaic folds or more recent faults.

            Following the highest ridge, the Mantiqueira range - from "Discovery Hill" or Easter Mountain (Monte Pascoal), on the extreme South of the coral reef coast, to the Southeast of the State of Minas Gerais - he reviews the most remarkable points of this chain (Flag Peak, 2 884 metres high; Itatiaia, 2 787 m); he mentions vestiges of ancient volcanoes in Poços de Caldas anel. Itatiaia, and refers to the high altitude of the Southeastern part, where (Campos de Jordão) a "four-season climate" prevails. Between the Paraiba do Sul and Araranguá rivers extends the ridge nearest to the ocean - the Serra do Mar - causing a very indented coast line, with penínsulas and numerous bays (some of these are true "rias" os estuaries), forming a wide arch from the Cape of São Tomé to that of Santa Marta - the Gulf of Santos -, as the author calls it. He further stresses the importance of the economic contribution of the Serra do Mar by its dense growth of "closed forest"; by its granite-gneissic rocks; by its numerous waterfalls and by the mild altitude climate. Far beyond the extreme South of the Serra do Mar, in the Southeast of Rio Grande do Sul, appear again the granite-gneissic rocks of the Brazilian Crystalline Complex, with half-orange prominences that extend into the Republic of Uruguai up to the mouth of the River Plate estuary, the "cattle bowls" (abobadas de pecuária) as the author names them, as these hills are covered with verdant pasture.

            In the South of the country, West of the Serra do Mar, rises the rampart of the Serra Geral, the Southern slope of the plateau, composed of sedimentary permo-triassic rocks, overlaid with thick sheets of sedimentary rocks. At the foot of this chain, in Santa Catarina and Rio Grande do Sul, are found the Brazilian coal deposits, in permian layers. The Southern heights of the plateau, with four-season climate, are covered with pine trees (Araucaria brasiliensis), with "steppe" here and there. Further North the dcomposition of the eruptive rocks was the origin of the famous "purple land", the best soil for coffee.

            Studying the Serra do Espinhaço, which extends East of Minas Gerais towards the North, reaching Baía, the author refers to the mineral wealth of this region (iron, manganese, coal, diamonds etc.), which inspired the famous verse of Gorceix: "Minas possesses a heart of gold in a chest of iron". West of these elevations lie the valley of the São Francisco and, beyond, the great table-lands (chapadões) in the boundaries of Minas Gerais and Baía with Goiaz, where ancient authors had erroneously imagined to exist chains. of mountains, under the name of "Espigão Mestre". ·

            Referring to the Northeastern prominence, he points out the contrast in climate existing the plains of the littoral, damp (formerly covered with "closed forest") - where the great sugar cane cultivation has been developping since the 17th century -.,.. and the high table-lands West of Borborema, with a scant pluviometric rate and a withered  jandscape, Which the author compares with Arizona and calls the "Northeastern desert of stone : and sand'. Next he indicates the differences from the point of view of: age, formation and aspect between the rupture ramparts of the mountain chains of Ibiapaba, in the Northeast, and the Geral, in the South. At the same time he remarkes upon the existence of fracture and collapse lines, which intersect at right angles forming quadrangular blocks, in the relief. The figures thus formed, with elbows which the rivers accompany, are called by the author "fracture quadrangles", probably caused by the isostatic fall resulting from the Andean upheaval.

            The extreme Northeast of the Brazilian plateau, between the Borborema hump and the parapet of the Ibiapaba chain, was named by the author the "Northeastern peneplain", owing to the fact that the crystalline complex presents itself there considerably depressed by erosion. In this "peneplain" rise up several flat-capped mounds covered with· cretaceous, constituting true witness hills (buttes de témoins). Upon some of these terraces (such as the Baturité and Meruoca chains) the humidity coming from the sea is condensed, thus causing what the author terms altitude oases, as regards to the desert peneplain. '

            With reference to our interior, he gives it the suggestive name of Far West, whose maps still show unexplored patches. This region, whose main sources of economy are cattle-raising and prospecting for gold and diamonds ("garimpagem"), still possesses hideouts of Indian tribes.

            The author then dwells briefly on the badly plotted divisions of the hydrographic basins, owing to the considerable washouts by the rivers in the old table-lands, which permit the joining of the waters of various basins by means of channels, known as "varadouros".

            Finally, he criticizes the teaching of facts that do not exist, as well as the interminable and inexpressive list of names, which have been hel as if condensing the whole study of Brazilian orography