Pangaea
Pangaea was the supercontinent that contained nearly all of Earth's landmasses about 300 million years ago before breaking apart.
Definition
Pangaea was a giant supercontinent that existed long before dinosaurs ruled, when all the continents we know today were squished together into one huge piece of land surrounded by one enormous ocean. It was assembled by the late Paleozoic, about $300$ million years ago, when Gondwana (South America, Africa, India, Australia, Antarctica) collided with Laurasia (North America, Europe, Asia), and it began rifting apart in the Triassic and Jurassic about $200$ million years ago, opening the Atlantic Ocean. Its existence is supported by matching fossils, rock sequences, mountain belts, and paleoclimate evidence across the modern continents. Pangaea formed through the closure of the Rheic and Iapetus oceans during the Alleghanian, Variscan, and Uralian orogenies, reaching maximum assembly around $300$ to $250$ million years ago. Its interior lay far from oceanic moisture, producing extreme continental climates and widespread red beds and evaporites, and its assembly is linked to reduced shallow-marine habitat and, with Siberian Traps volcanism, to the end-Permian extinction. Breakup began with the Central Atlantic Magmatic Province at about $201$ million years ago, coincident with the end-Triassic extinction, and proceeded through the opening of the central Atlantic, then the South Atlantic and Indian Ocean.
Example
When Pangaea existed, you could have walked from North Carolina to Morocco without crossing any ocean, because Africa was pressed right against the Carolinas. The Appalachian Mountains were raised by the collision that built Pangaea, when Africa rammed into North America, and the Triassic rift basins near Durham and Sanford, North Carolina, filled with sediment as Pangaea began to split. CAMP basalt dikes cut across the North Carolina Piedmont and the Triassic basins, recording the volcanic pulse that split the supercontinent. Paleomagnetic reconstructions place the Carolinas near the equator during Pangaea's assembly.
Key Insight
The name means "all lands" in Greek, and the single ocean around it was called Panthalassa, "all seas." Pangaea was not the first supercontinent and will not be the last; earlier ones such as Rodinia formed and broke up in a cycle that repeats every few hundred million years. The supercontinent cycle links deep Earth to climate and life. Assembly concentrates continents, disrupts ocean circulation, and lowers sea level, while breakup floods continental margins, raises sea level, and isolates populations, which drives speciation.