Pangaea: The Supercontinent That United All of Earth's Land

Pangaea was a supercontinent that joined almost all of Earth’s land into a single mass between about 335 and 175 million years ago. Stretching from pole to pole and surrounded by a vast global ocean called Panthalassa, it shaped the planet’s climate and the evolution of life, from the early reptiles to the first dinosaurs. The idea of Pangaea, first argued by Alfred Wegener in the early 20th century, became a cornerstone of modern geology once plate tectonics explained how continents move.

What Pangaea was

The name comes from the Greek words pan, meaning “all”, and gaia, meaning “earth” or “land”. At its greatest extent Pangaea included the land that now forms the Americas, Europe, Africa, Asia, Antarctica, Australia and India. It was roughly C-shaped, with a large bay of ocean on its eastern side called the Tethys Ocean, or in its earlier form the Paleo-Tethys.

Geologists often divide Pangaea into two halves. The northern part, made up of North America, Europe and much of Asia, is called Laurasia. The southern part, made up of South America, Africa, Antarctica, India and Australia, is called Gondwana. Gondwana had existed as a large continent long before Pangaea formed.

Pangaea was not the first supercontinent. Earlier ones include Rodinia, which assembled about 1.1 billion years ago and broke up around 750 million years ago. Geologists see Pangaea as the most recent stage in a long “supercontinent cycle” of assembly and break-up.

How Pangaea assembled

Pangaea formed gradually through a series of continental collisions in the late Paleozoic Era. The most important was the collision between Gondwana and Laurussia, a northern continent that included North America and northern Europe.

As these continents converged during the Carboniferous Period, from roughly 335 million years ago, the ocean between them closed. The collision raised a long chain of mountains known in Europe as the Variscan or Hercynian mountains and in North America as the Alleghanian part of the Appalachians and the Ouachita Mountains. The eroded roots of these ranges can still be seen in Cornwall, Brittany, the Massif Central, the Harz and the Appalachians.

Other blocks joined later. Siberia and the Kazakh region collided with eastern Europe in the late Carboniferous and Permian, raising the Ural Mountains. By around 300 to 250 million years ago Pangaea was essentially complete. Some East Asian blocks, such as North and South China, were attached late or were never fully joined, and the exact configuration remains a subject of research.

The world of Pangaea

Climate

Because Pangaea was so large, much of its interior lay thousands of kilometres from the sea. Moist ocean air could not reach these regions, so they became extremely dry. Vast deserts spread across its centre, leaving thick red sandstones and salt deposits in rocks of Permian and Triassic age, for example in Germany, Britain and the American Southwest.

Along its coasts, scientists think the huge contrast between land and sea produced powerful seasonal monsoons, sometimes called “megamonsoons”. In its early history, a large ice sheet covered the southern polar part of Gondwana. This ice age, which began before Pangaea was complete, ended during the early Permian, after which the planet became very warm, especially in the Triassic.

The single ocean

Surrounding Pangaea was Panthalassa, a single world ocean far larger than the Pacific today. With fewer separate coastlines, the total area of shallow continental seas, which are rich habitats for marine life, may have been reduced compared with times when continents were separated.

Life on Pangaea

Pangaea’s existence had major effects on the history of life. Because land animals could walk across most of the supercontinent, many groups spread widely. The same kinds of plants and reptiles are therefore found as fossils on continents that are now separated by oceans.

During the Permian Period, synapsids such as Dimetrodon, distant relatives of mammals, became the dominant large land animals. At the end of the Permian, about 252 million years ago, the Permian–Triassic extinction wiped out most marine species and many land animals. It is linked to massive volcanic eruptions in Siberia, which occurred on Pangaea’s surface.

In the recovery that followed, during the Triassic, new groups appeared. The first dinosaurs and early mammals evolved around 230 to 225 million years ago, when the land was still united. This is why early dinosaurs are known from Argentina, Brazil, India, southern Africa, Europe and North America.

Wegener’s evidence

The idea that the continents had once been joined was proposed in various forms in the 19th century. In 1858 the French geographer Antonio Snider-Pellegrini published a pair of maps showing the Americas fitted against Europe and Africa, although he explained the separation by catastrophe rather than slow movement. The German meteorologist and geophysicist Alfred Wegener developed it into a detailed theory. He first presented continental drift in January 1912 and expanded it in his book Die Entstehung der Kontinente und Ozeane (The Origin of Continents and Oceans), first published in 1915. He used the name Pangäa in the 1920 edition.

Wegener assembled several lines of evidence:

• The fit of the continents. The coastlines of South America and Africa fit together closely, and the fit is even better when the edges of the continental shelves are used.
• Matching rocks and mountains. Rock formations and mountain belts on opposite sides of the Atlantic match, for example between the Appalachians and the mountains of Scotland and Norway.
• Fossils. The small freshwater reptile Mesosaurus is found only in southern Africa and South America. The seed fern Glossopteris occurs across the southern continents, and later the land reptile Lystrosaurus was found in Africa, India and Antarctica.
• Ancient climates. Glacial deposits of the late Paleozoic ice age occur in India, Africa, South America and Australia, regions now far apart and partly in the tropics. Coal deposits, formed in warm swamps, are found in places now near the poles.

Many geologists rejected Wegener’s ideas, chiefly because he could not explain what force moved the continents. The British geologist Arthur Holmes proposed around 1929 to 1931 that slow convection currents in the mantle could drive them. The South African geologist Alexander du Toit supported drift with detailed field evidence in his book Our Wandering Continents (1937). Wegener himself died on an expedition to the Greenland ice sheet in November 1930.

From drift to plate tectonics

Acceptance came in the 1950s and 1960s. Studies of ancient magnetism preserved in rocks, called palaeomagnetism, showed that continents had changed position over time. Surveys of the ocean floor revealed mid-ocean ridges, seafloor spreading and symmetrical magnetic stripes. By the late 1960s these discoveries had been combined into the theory of plate tectonics, which provided the mechanism Wegener had lacked.

Today computer reconstructions use palaeomagnetic data, ocean-floor ages and the distribution of rocks and fossils to map Pangaea in detail. There is still debate over details, such as the exact positions of Laurasia and Gondwana relative to each other before the Jurassic.

Break-up

The break-up of Pangaea began with rifting in the Triassic. Around 201 million years ago a huge outpouring of lava known as the Central Atlantic Magmatic Province marked the start of the opening of the central Atlantic Ocean, and coincided with the end-Triassic mass extinction. From about 175 million years ago true ocean crust formed between North America and Africa.

Over the following tens of millions of years, Gondwana itself split apart. South America separated from Africa as the South Atlantic opened in the Cretaceous, India moved north towards Asia, and Australia and Antarctica separated in the Cenozoic. The continents are still moving today, at rates of a few centimetres a year.

By the numbers

Timeline

• c. 335 million years ago: Gondwana and Laurussia collide, beginning the main assembly of Pangaea.
• c. 300–250 million years ago: Siberia joins and the Urals rise; Pangaea is essentially complete.
• c. 252 million years ago: The Permian–Triassic extinction strikes life on and around Pangaea.
• c. 230 million years ago: The first dinosaurs appear on the united supercontinent.
• c. 201 million years ago: Volcanism in the Central Atlantic region marks the start of break-up.
• c. 175 million years ago: The central Atlantic Ocean begins to open.
• 1912, January: Alfred Wegener presents his theory of continental drift.
• 1920: Wegener uses the name Pangäa in the second edition of his book.
• 1937: Alexander du Toit publishes Our Wandering Continents.
• 1960s: Plate tectonics confirms that the continents move.

Why it matters

Pangaea explains why the same fossils, rocks and ancient ice ages appear on continents now separated by oceans. Its assembly and break-up shaped global climate, sea levels and the spread and extinction of life, from early reptiles to dinosaurs. The story of how Pangaea was recognised, from Wegener’s rejected theory to plate tectonics, is also one of the great scientific revolutions of the 20th century.