supercontinents

Supercontinents are vast landmasses composed of most of Earth's continental crust that form when separate continents collide and fuse through plate tectonics. They arise as part of the long-term supercontinent cycle, in which continental plates assemble into a single mass and later disperse again into smaller continents over hundreds of millions of years.

Over geologic time several candidates have been proposed. Nuna (also called Columbia) is one of the earliest proposed supercontinents, dating to about 1.8–2.0 billion years ago and beginning to break apart around 1.5–1.3 billion years ago. Rodinia formed around 1.3–0.9 billion years ago and disassembled roughly 750–600 million years ago. Pannotia is posited to have existed around 600–540 million years ago before fragmenting. Pangaea, the best known, assembled around 335 million years ago and began breaking apart in the early Jurassic, about 175 million years ago, giving rise to the continents we know today.

Evidence for these configurations comes from paleomagnetism, correlation of rock sequences across continents, and the distribution of similar fossils and mineral deposits. Modern reconstructions use plate tectonic models to test various configurations against geological and geochemical data.

The existence and timing of supercontinents have implications for Earth systems, including climate, ocean circulation, mountain-building, and biodiversity. Periods of assembly can coincide with the formation of major mountain belts and shifts in weathering and carbon cycling, while breakup often opens oceans and promotes diversification.

The concept of the supercontinent cycle remains a subject of research and debate. Estimates of cycle length and the exact timings of assembly and breakup vary among scientists, and some proposed configurations are contested as new data emerge.