supercontinent

n.
A large hypothetical continent, especially Pangaea, that is thought to have split into smaller ones in the geologic past. Also called protocontinent.

The six major continents today are Africa, Antarctica, Australia, Eurasia, North America, and South America. Prior to the formation of the Atlantic, Indian, and Southern ocean basins over the past 180 million years by the process known as sea-floor spreading, the continents were assembled in one supercontinent called Pangea (literally “all Earth”). Pangea came together by the collision, about 300 million years ago (Ma), of two smaller masses of continental rock, Laurasia and Gondwanaland. Laurasia comprised the combined continents of ancient North America (known as Laurentia), Europe, and Asia. Africa, Antarctica, Australia, India, and South America made up Gondwanaland (this name comes from a region in southern India). The term “supercontinent” is also applied to Laurasia and Gondwanaland; hence it is used in referring to a continental mass significantly bigger than any of today's continents. A supercontinent may therefore incorporate almost all of the Earth's continental rocks, as did Pangea, but that is not implied by the word. See also Continent; Continents, evolution of.

Laurasia, Gondwanaland, and Pangea are the earliest supercontinental entities whose former existence can be proven. Evidence of older rifted continental margins, for example surrounding Laurentia and on the Pacific margins of South America, Antarctica, and Australia, point to the existence of older supercontinents. The hypothetical Rodinia (literally “the mother of all continents”) may have existed 800–1000 Ma, and Pannotia (meaning “the all-southern supercontinent”) fleetingly around 550 Ma. Both are believed to have included most of the Earth's continental material. There may have been still earlier supercontinents, because large-scale continents, at least the size of southern Africa or Western Australia, existed as early as 2500 Ma at the end of Archean times. See also Archean; Continental margin.

The amalgamation and fragmentation of supercontinents are the largest-scale manifestation of tectonic forces within the Earth. The cause of such events is highly controversial. See also Plate tectonics.

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