Half of Brazil stands on the Brazilian Highlands, or Planalto Brasileiro: an ancient upland of about 4.5 million km² covering most of the country's east, south and centre. Geographers divide it into the Atlantic Plateau along the coast, the Southern Plateau of basalt-capped sediments, and the Central Plateau of the interior, with ranges such as the Serra do Mar, Serra da Mantiqueira, Serra do Espinhaço and Chapada Diamantina rising above them. Its highest point is Pico da Bandeira, 2,891 m, in the Serra do Caparaó. The São Francisco, Paraná and many smaller rivers rise here, and the great majority of Brazil's 203 million people (2022 census) live on the highlands or on the narrow coast beside them. It has no active volcano or significant earthquake zone today. Billions of years of crust-building, lava floods and erosion made it, so the account below starts with the oldest rock and works upwards.
São Francisco Craton: The Archaean Core of Minas Gerais and Bahia
The foundation is the São Francisco Craton, an ancient block of crust that crops out in Minas Gerais and Bahia. It is made of several pieces of Archaean basement, more than 2.5 billion years old, separated by belts of younger deformed rock. Most of those belts, with their sedimentary basins and granite intrusions, formed in the Palaeoproterozoic, about 2.5 to 2.0 billion years ago, which set the craton's present shape.
The craton has moved between supercontinents. Around a billion years ago it lay in the south of Rodinia; after Rodinia broke apart in the late Proterozoic, about 700 million years ago, it became part of Gondwana. Its twin is the Congo Craton in Africa, from which it separated when the South Atlantic opened. That connection is why geologists match rock belts on both sides of the ocean.
Iron Quadrangle: Gold and Iron from 2.5-Billion-Year-Old Seabeds
On the craton's southern edge lies the Quadrilátero Ferrífero, or Iron Quadrangle, a mineral district of about 7,000 km² in south-central Minas Gerais. Its ore sits in the Minas Supergroup, metamorphosed sediments first laid down about 2.5 billion years ago, and the region supplied roughly 40% of all gold produced in Brazil between 1500 and 2000, along with diamonds and iron ore.
The rocks then steered Brazilian history. Gold was known here from 1690, and the Brazilian Gold Rush that followed drew hundreds of thousands of migrants from Europe and northern Brazil. At least half a million enslaved Africans were taken to work the mines, and the Portuguese crown took 20% of production in tax. More than 4 million people now live in the Iron Quadrangle, centred on Belo Horizonte, and the district's dependence on mining has had a price: two large tailings dams collapsed there in the 2010s, causing extensive damage and loss of life.
Espinhaço Ridges and the Tablelands of Chapada Diamantina
Running north from the Iron Quadrangle, the Serra do Espinhaço extends about 1,100 km north to south through Minas Gerais and Bahia. It is a drainage divide, sending water west to the upper São Francisco and east to the Doce, Jequitinhonha and Pardo, and it peaks at Pico do Sol, 2,081 m, in the Caraça reserve near Catas Altas. The historic mining town of Diamantina lies in these mountains, which served as a main route for settling Minas Gerais during the 18th-century gold rush.
The range's northern end is the Chapada Diamantina, the "Diamond Plateau" of central Bahia, about 38,000 km² across 58 municipalities. Here erosion has cut the plateau into flat-topped mesas, deep canyons and waterfalls; the Sincorá Ridge alone runs 160 km north to south and 20 to 30 km wide. Most of the region lies above 500 m, it is cooler than the surrounding caatinga, and its trails were first worn by diamond miners. Lençóis, Mucugê, Andaraí and Palmeiras mark its corners, with Morro do Pai Inácio and the Vale do Pati among its best-known landscapes.
Brasiliano Orogeny: The Neoproterozoic Collision That Built Gondwana
Around and between the cratons lie belts of rock deformed in a series of Neoproterozoic mountain-building events, exposed chiefly in Brazil and known as the Brasiliano orogeny, a term coined by Almeida and colleagues in 1973. It is the South American half of the Pan-African orogeny that assembled much of Gondwana, and it closed several former oceans, among them the Adamastor and Goianides oceans. Matching individual Brasiliano belts with their African counterparts remains difficult, but the overall picture is of continents colliding and their margins being squeezed into high-grade metamorphic rock.
High-grade metamorphic rock also crowns the highest ground in eastern Brazil. Pico da Bandeira, on the border of Minas Gerais and Espírito Santo inside Caparaó National Park, has a summit of migmatite surrounded by granulitic gneiss. It was considered Brazil's highest mountain until 1965, when Pico da Neblina and Pico 31 de Março near the Venezuelan border were measured and found to be higher. It is still the highest peak outside the Amazon and has a topographic isolation of 2,344 km, greater than all but 20 mountains on Earth.
Paraná Basin: 7,000 Metres of Ordovician-to-Cretaceous Sediment
Inside the assembled Gondwana, a vast cratonic basin took shape. The Paraná Basin, an elliptical depression of about 1.5 million km², began to fill in the Paleozoic and kept collecting sediment until the end of the Cretaceous, between roughly 460 and 66 million years ago. About 75% lies in Brazil, from Mato Grosso to Rio Grande do Sul, with the rest in Paraguay, Argentina and Uruguay, and its fill reaches 7,000 m thick at the centre. For part of the Paleozoic it was a gulf open to the south-west.
The basin preserves Gondwana's shared past. In his 1908 report on Brazilian coal, the American geologist Israel C. White described Mesosaurus fossils in Permian black shales of the Irati Formation and Glossopteris plants in the Permian coals, and he was among the first to match these beds with the Karoo Basin in South Africa. Higher in the pile come wind-blown sandstones of the Botucatu Formation, laid down in an arid desert of dunes, salt flats and wadis. Together with the river-laid sandstones of the Pirambóia Formation, they hold the Guarani Aquifer, one of the world's largest, spreading under about 1.2 million km² of Argentina, Brazil, Paraguay and Uruguay and storing an estimated 37,000 km³ of water.
Paraná Traps: The Lava Floods of 132 Million Years Ago
Then came lava. Between about 136 and 132 million years ago, as rifting began to pull Africa and South America apart, a mantle plume fed one of Earth's great flood-basalt eruptions: the Paraná–Etendeka large igneous province. After the eruptions the lava covered about 1,000,000 km², with an original volume estimated at more than 2.3 million km³. The smaller Etendeka traps were carried away to north-west Namibia and south-west Angola as the Atlantic widened, and the same rifting may also lie behind Tristan da Cunha and Gough Island, which are joined to the province by the Walvis Ridge.
These lavas, the Serra Geral formation, form the cap of the Southern Plateau. More than 90% of the Guarani Aquifer lies under them, the low-permeability basalt sealing the sandstone below. Where basalt partly covers the older sediments, the result is the fertile ground known as "purple land". Where rivers cut through it, the layers show as steps. At Iguazu Falls, on the border between Brazil's Paraná state and Argentina's Misiones province, the river drops in two steps of 35 and 40 m over three basalt layers within a 1,000 m thick Serra Geral sequence, along an edge 2.7 km long split into 150 to 300 separate falls depending on the water level.
South Atlantic Rifting and the Serra do Mar Escarpment
Gondwana's break-up, which began around 180 million years ago in the Jurassic, eventually opened the South Atlantic and gave Brazil its coast. The Atlantic Plateau now ends in the Great Escarpment, which runs along much of the eastern coast south of Salvador. Its best-known section is the Serra do Mar, a 1,500 km system of ranges and escarpments from Espírito Santo to southern Santa Catarina that separates the sea-level coast from an inland plateau averaging 500 to 1,300 m. Most of its present elevations formed about 60 million years ago, and Pico da Caledônia near Nova Friburgo reaches 2,255 m.
Inland and parallel to it rises the Serra da Mantiqueira across São Paulo, Minas Gerais and Rio de Janeiro. Pedra da Mina, at 2,798 m, was confirmed by GPS as the range's highest point, edging out Pico das Agulhas Negras, 2,792 m, in Itatiaia National Park. Winter nights here fall to near or below 0 °C. The Atlantic Plateau was once almost entirely covered by Atlantic Forest; only about 7.3% survives, and in the Serra do Mar what remains is concentrated on the steep slopes facing the sea.
São Francisco, Cerrado and Brasília on the Central Plateau
The uplands decide where Brazil's water goes. The São Francisco rises in the Serra da Canastra of Minas Gerais and flows 2,914 km, the longest river entirely within Brazil, draining over 630,000 km² as it runs north behind the coastal ranges and then east to the Atlantic. Brooks of the Mantiqueira feed the Grande River, a source of the Paraná, whose hydroelectric chain includes the Itaipu Dam on the Brazil–Paraguay border, built between 1970 and 1984.
On the Central Plateau the dominant landscape is the Cerrado, a tropical savanna of about 2 million km², 21% of Brazil's land area, which WWF calls the biologically richest savanna in the world, with about 10,000 plant species; about 85% of the Central Plateau was once covered by it. The plateau's height and central position also made it the site of the capital. Brazil's 1891 constitution reserved 14,400 km² on the central plateau for a future federal district, the Belgian astronomer Luís Cruls surveyed it in 1892 and 1894, and Brasília now stands at about 1,170 m, its tropical climate made milder by that elevation. To see the basalt staircase up close, read our guide to Iguazu Falls; for the forest that once cloaked the escarpments, explore the Atlantic Forest; and to follow the capital built on the plateau, visit our profile of Brasília.