Brazilian Highlands(redirected from Planalto Central)
highlands occupying a large part of eastern South America, from 3° to 35° S lat., primarily in Brazil; on the south they are in Uruguay, and on the southwest their edge extends into Paraguay and Argentina. They are very high on the east and southeast above the Atlantic coast (Mount Bandeira, 2,890 m) and slope gently on the north toward the Amazon Basin and in the southwest toward the La Plata basin; in the northwest they break toward the upper Paraguay lowlands.
The Brazilian Highlands consist of ancient crystalline shields and syneclises filled in by sedimentary and volcanic rock.
In the topography, the shields are expressed primarily by socle plains 250–300 m in elevation to the north and 800–900 m in the center, with individual butte peaks or clumpy blocks up to 1,350 m high (the Goiás highlands). The Atlantic shield is strongly broken by faults and breaks away sharply toward the ocean, which gives the eastern slopes the appearance of mountain ridges (Portuguese serra): Serra do Mar (1,889 m), Serra da Mantiqueira (2,787 m), and others. Individual crystalline blocks in the hot and moist climate take on the specific form of’ sugar loaves.’ The Brazilian Highlands are framed on the northeast and east by narrow sections of the Atlantic lowlands. Along the right bank of the Sāo Francisco River the pointed sedimentary Proterozoic ridges of Serra do Espinhaço rise to 1,500–2,100 m. Syneclises (in the states of Maranhāo and Piauí and along the Sao Francisco River, the upper Paraná, and others) are usually represented by layered plains, often with erosion steps of the cuesta type; in the more elevated regions they are represented by butte sandstone table plateaus with steep shoulders (chapadas; they are characteristic for an unfolded cover foundation as well). Only the Paraná basin is a folded lava plateau.
The Brazilian Highlands lie in the subequatorial, tropical, and subtropical climatic belts. The average temperature in January ranges from 22° C in the southwest to 29° C in the northeast (the maximum reaches 42° C); in July it ranges from 12° to 25° C, with a minimum of 6° C in the tropics. The amount and pattern of precipitation within the Brazilian Highlands is quite varied: in the north and in the central regions, precipitation occurs mainly in the summer, up to 1,400–2,000 mm annually (in the northeast, the driest region, there is less than 500 mm); in the east there is over 2,000 mm, almost without a drought, and in the south, 1,000–1,800 mm annually.
In the river system, there is usually a sharp decrease in runoff during the winter and tumultuous flooding in the summer. Runoff from the north and northwest of the Brazilian Highlands comes from the basins of the right tributaries of the Amazon (the Madeira, Tapajós, Xingú, and the Tocantins and Araguaia); runoff from the northeast and east is toward the basins of the Parnaiba, the Sao Francisco, and other rivers that flow into the Atlantic Ocean; and from the southwest and south, the runoff is toward the basins of the Paraná and Uruguay rivers. The rivers abound with rapids and waterfalls, which create large hydroelectric resources but hinder navigation.
In the northwest and north the Brazilian Highlands are covered with moist evergreen and deciduous-evergreen forests; in the center there are shrub savannas (campos cerrados); in the northeast there is xerophytic-succulent sparse forest (caating); in the east there are tropical rain forests, evergreen or green in summer; and in the south there are mixed forests of conifers with evergreen leaf-bearing trees and a treeless savanna (campos limpos).
E. N. LUKASHOVA