Pangaea

Pangaea was the most recent supercontinent to incorporate almost all of Earth's major landmasses. Its assembly took place over geological time as continental fragments moved and collided. Britannica dates its completed assembly to the Early Permian, about 299–273 million years ago; the National Park Service describes the joined landmass as a snapshot from roughly 250 million years ago. Pangaea was surrounded by the vast ocean Panthalassa. A curved embayment on its eastern side formed the Tethys sea region. The exact outlines of land and sea changed over time, so reconstructions depict a sequence rather than one unchanging map.

Pangaea did not split apart in a single event. Rifting began roughly 200 million years ago, and the supercontinent fragmented in stages as parts of Earth's lithosphere moved apart. In one early rift system, separation among Africa, South America and North America helped open the Atlantic basin; later movements further divided the southern continents and opened other ocean basins. The U.S. Geological Survey describes how rifting and volcanic activity along the separating landmasses contributed to the growth of the Atlantic and the mid-Atlantic ridge. The process continues in the sense that Earth's tectonic plates are still moving, although the present-day continental arrangement developed over many millions of years.

The idea that continents had once been joined gained support from their complementary shapes, especially the margins of South America and Africa, and from geological patterns found across now-separated regions. Alfred Wegener developed the concept of Pangaea as part of his continental-drift hypothesis in the early twentieth century. The idea was initially controversial because Wegener could not provide a convincing mechanism for continental motion. Plate tectonics later supplied a broader physical framework: Earth's outer shell is divided into plates that move relative to one another. Pangaea is one reconstructed episode in Earth's longer history of supercontinent assembly and breakup, not the only supercontinent that has existed.