Brazil's geography: an old plateau whose rivers turn from the sea

Why Brazil has no high mountains

Brazil sits on ancient rock. Precambrian crystalline shields make up 36% of the territory, mostly in the centre, and this rock has not been lifted by any recent mountain building. The Andes to the west rose to nearly 7,000 metres in a geologically recent epoch and reversed the flow of the Amazon from westward to eastward; the Brazilian shield has only been eroded. The granite domes of Rio de Janeiro, Sugar Loaf among them, are what tens of millions of years of weathering leave behind on a basement rock that nothing has pushed upwards.

The numbers follow from that. About 41% of the country averages less than 200 metres above sea level, and only about 0.5% rises above 1,200 metres. The principal ranges average under 2,000 metres. The central plateau, the Planalto Central, has an uneven surface averaging about 1,000 metres, and São Paulo, Belo Horizonte and Brasília all sit at roughly that height, which keeps their temperatures moderate at a latitude where the coast is hot.

The highest ground is at the far edges. Pico da Neblina, at 2,994 metres, stands in the far north, where the highest ranges run along the borders with Venezuela and the Guianas and the Guiana Highlands divide the water running south to the Amazon from the water running north to the Orinoco. In the southeast the Serra da Mantiqueira reaches 2,890 metres at Bandeira Peak and 2,787 metres at Agulhas Negras. The Serra do Espinhaço runs from central Minas Gerais into southern Bahia and reaches 1,850 metres at Almas Peak.

How the escarpment walls off the coast

The shield ends at the Atlantic in a steep rim. The Serra do Mar, averaging about 1,000 metres, runs from southeastern Minas Gerais to eastern Paraná, and near Rio de Janeiro, where it is also called the Serra dos Órgãos, it presents an almost sheer face to the sea. Farther south the rim continues as the Serra de Botucatu in São Paulo state and the Serra Geral from Paraná southwards.

In front of it the coastal plain is narrow. Britannica describes the Atlantic lowlands as a tiny part of the national territory, up to 200 kilometres wide in the north, narrower in the northeast and absent in parts of the southeast. Where the rock plunges straight into the sea it forms deep natural harbours, Guanabara Bay at Rio de Janeiro and All Saints Bay at Salvador, and the cities built there occupy small valleys and strips of flat ground, with poorer districts climbing the steep ridges behind.

Offshore, Brazil holds the archipelago of Fernando de Noronha, about 350 kilometres northeast of the coast's eastern bulge, and the smaller Atlantic islands and atolls of Rocas, Trindade, Martim Vaz and the rocks of São Pedro e São Paulo. Its exclusive economic zone measures 3,830,955 square kilometres.

Two sources give two lengths for the coast: 7,367 kilometres in the Wikipedia article on Brazil's geography and 7,491 kilometres in its article on the country. The land borders run for 15,719 kilometres against ten neighbours, every South American country except Chile and Ecuador, and a few short sections are in question without any major boundary dispute.

The wall shaped the history as much as the relief. For the first two centuries of the colony the highlands behind the escarpment were close to inaccessible and were crossed only by bandeirante expeditions from São Paulo. The centre of the colony moved from the northeast to the southeast only after gold was found in Minas Gerais in 1695 and settlers built roads over the Serra do Mar to the coast. The capital followed, from Salvador to Rio de Janeiro, in 1763.

Why the long rivers run inland

Brazil has eight major drainage basins, and every one of them ends in the Atlantic. What the escarpment decides is the route. The streams that drain directly east from the highlands are short, steep and of little use for boats or dams. The long rivers rise on the plateau behind the rim and flow away from the coast.

The Amazon rises in the Peruvian Andes within 160 kilometres of the Pacific and runs some 6,400 kilometres to the Atlantic, where it contributes as much as a fifth of all surface runoff from the continents to the sea. About 3,615 kilometres of it lie in Brazil, and over that distance the water drops only about 100 metres. Ships of considerable size reach Manaus, and smaller vessels continue to Iquitos in Peru, about 3,700 kilometres from the sea. Its annual discharge is more than ten times that of the Mississippi, and six of its tributaries exceed 1,600 kilometres. The tributaries themselves are broken by falls and rapids where they come down off the highlands, so the plateau stops river traffic even here.

The Paraná system rises in the highlands of Mato Grosso, Goiás and Minas Gerais and flows south. Its Brazilian tributaries, the Tietê, the Grande, the Paranapanema and the Iguaçu, all carry hydroelectric dams and reservoirs. Itaipu, on the Paraná, has 12,600 MW of capacity, and when it was completed in 1982 its reservoir drowned the Guaíra Falls. The Iguaçu falls over a rim of diabase in southwestern Paraná to form the Iguaçu Falls.

The São Francisco rises in western Minas Gerais and southern Goiás, flows northward for more than 1,600 kilometres and only then turns east to the ocean. Riverboats work the stretch between Pirapora and Juazeiro. Only the 277 kilometres below the Paulo Afonso Falls take oceangoing ships.

Where the rain falls and where it fails

About 74% of Brazil lies within the tropics. The equator crosses the mouth of the Amazon and the Tropic of Capricorn crosses the country at the latitude of São Paulo, and the Wikipedia article on Brazil notes that no other country has both lines running through it.

Most of the country receives between 1,000 and 1,800 millimetres of rain a year. The Amazon gets more than 2,000 millimetres, and up to 3,000 in parts of the west and near Belém, yet even the rainforest has a dry season of three to five months. Rainfall is also much heavier than average on the sea-facing rim of the Serra do Mar.

The exception is the northeastern interior, the sertão. A zone Britannica calls the drought quadrilateral, reaching from northern Bahia to the coast between Natal and São Luís, receives only 375 to 750 millimetres a year, and droughts there run in cycles averaging seven years. It is also the hottest part of the country, with January averages of about 29°C and daytime temperatures above 38°C. The Great Drought of 1877 and 1878 caused approximately half a million deaths, and drought is one of the main reasons people have left the region, first in the 1870s and 1880s for the rubber forests of the Amazon and in the mid-twentieth century for the building of Brasília. In 2024 a drought covered almost 60% of the national territory.

Winters in the south bring frost. Near-freezing temperatures can reach as far north as São Paulo, snow falls in the highest parts of Paraná, Santa Catarina and Rio Grande do Sul, and Curitiba, at about 900 metres, averages 14°C in June and July, when Rio de Janeiro averages 23°C.

Which biomes cover the country

The Amazon rainforest covers the north. Britannica records that a typical acre of it may hold 250 or more tree species, that the closed canopy lets no more than a tenth of the sunlight reach the ground and that about 1,500 fish species have been identified in its waters. South and east of it the forest gives way to the cerrado, a savanna of grasses and twisted small trees across most of central Brazil, and in the dry northeast to the caatinga, a thorny, stunted woodland whose name comes from an Indigenous term for white forest.

The Pantanal, at the headwaters of the Paraguay River in the west, is a seasonally flooded plain covering up to 230,000 square kilometres. The Atlantic Forest once ran the length of the eastern seaboard; more than 90% of it had been cleared by 1996, mainly for farming, and it now holds 171 of the 202 animals listed as endangered in Brazil. Araucaria pine forests covered the southern plateaus, and grassland like the Argentine pampa covered the far south; both have been largely replaced by fields and pasture.

The soils under all this are mostly poor. Heavy rain has leached much of the highland ground, leaving laterites that can run 27 metres deep, and Amazonian soils lose their nutrients quickly once the canopy above them is cut or burned. The fertile exceptions are the deep reddish terra roxa of Paraná and São Paulo, which carries the country's most heavily farmed land, the alluvial várzea along the Amazon floodplain and the terra preta, the black earth that formed on the sites of prehistoric settlements.

Forest covered about 59% of the land in 2020, some 496.6 million hectares, down from 588.9 million hectares in 1990. In 2017 preserved native vegetation occupied 61% of the territory, crops 8% and pasture 19.7%.

How fast the Amazon forest is being cleared

The National Institute for Space Research, INPE, has mapped clearance across the Legal Amazon every year since 1988 through its PRODES programme, which counts the complete removal of primary forest cover. Its consolidated figure for the year from 1 August 2024 to 31 July 2025 is 5,731 square kilometres, 12.07% less than the 6,518 square kilometres of the year before. Eight of the nine states of the Legal Amazon cleared less; Mato Grosso cleared 26.73% more.

The longer total is far larger. More than 600,000 square kilometres of the Amazon rainforest have been cleared since 1970, according to the Wikipedia article on Brazil. The federal environment agency, IBAMA, was created in 1989 to enforce the law, and Britannica records that in 2023 it had about 700 enforcement agents, some 150 of them available for field work at any one time, relying on satellite monitoring to find illegal clearing.

Where Brazilians live on this land

The five official regions divide the country very unevenly, and the population divides it in the opposite direction.

In 1991 the Southeast held 63 million people, 39% of the national total, while in 1996 the whole North held 11.1 million, 7% of it. The settlement history explains the gap. The Amazon had an estimated 40,000 inhabitants in the mid-nineteenth century and some 1.4 million by the end of the First World War, after the rubber boom drew migrants from the northeast. The southeastern plateau filled with coffee, European immigrants and industry from the late nineteenth century. Brasília was placed on the central plateau, inaugurated in 1960, to pull settlement inland, and Britannica records that government efforts to populate the Amazon have had limited success.