Supercontinent
Encyclopedia : S : SU : SUP : Supercontinent
In geology, a supercontinent is a land mass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form EurasiaAnd to a lesser extent, the Americas, if taken as a whole qualifies as a supercontinent today.
History
Most commonly, paleogeographers employ the term supercontinent to refer to a single landmass consisting of all the modern continents. The earliest known supercontinent, Rodinia, broke up roughly 750 million years ago. One of the fragments included large parts of the continents now located in the southern hemisphere. Plate tectonics brought the fragments of Rodinia back together in a different configuration during the late Paleozoic era, forming the best-known supercontinent, Pangaea. Pangaea subsequently broke up into the northern and southern supercontinents, Laurasia and Gondwana.Modern studies have suggested that supercontinents form in cycles, coming together and breaking apart again, through plate tectonics, very roughly about every 250 million years. Recently, Drs. John J. Rogers and M. Santosh have proposed the existence of an older supercontinent, Columbia, which formed and broke up during a period of 1.8 to 1.5 billion years (1.8-1.5 Ga) ago.
Geology
Supercontinents block the flow of heat from the Earth's interior, and thus cause the asthenosphere to overheat. Eventually, the lithosphere will begin to dome upward and crack, magma will then rise, and the fragments will be pushed apart. It is currently a matter of some debate as to how the supercontinents reform, whether or not plate tectonics makes them re-join after travelling around the planet, or if they move apart and then back together again.In other areas of study such as history and geography, land masses connected with an isthmus are also considered supercontinents or just continents, such as the Americas. Some historians call the combined land mass of Africa and Eurasia the supercontinent Africa-Eurasia, but it is not a geological supercontinent.
Incomplete list of major past supercontinents
Incomplete list of supercontinents
In reverse-chronological order (stratolithic order) comprising nearly all land at the time.
- Pangaea Ultima or Amasia (~250 – ~400 million years from now)
- Eurasia ''(present-day supercontinent)
- Pangaea (~300 – ~180 million years ago)
- Pannotia (~600 – ~540 million years ago)
- Rodinia (~1.1 Ga – ~750 million years ago)
- Columbia (~1.8–1.5 Ga ago)
- Kenorland (~2.7 new continental crust formed Kenorland from Neoarchean sanukitoid cratons. Protracted tectonic magna plume rifting occurred 2.48 to 2.45 Ga - possibly contributed to the Paleoproterozoic glacial events in 2.45 to 2.22 Ga. Final breakup occurred ~2.1 Ga.)
- Ur (~3 Ga ago, though probably not a supercontinent; but still however, the earliest known continent. Ur, however, was probably the largest, perhaps even the only continent three billion years ago, so one can argue that Ur was a supercontinent for its time, even if it was smaller than Australia is today). Still an older rock formation now located in Greenland dates back from hadean
- Komatii Formation (3.475 Ga)
- Vaalbara (~3.6 Ga ago. Evidence is the Yilgarn Craton, Western Australia and the world-wide Archean greenstone belts that were subsequently spread out across Gondwana and Laurasia)
Notes
External links
- [Palaeos.com]: General earth history
- [The Paleomap Project — Christopher R. Scotese]
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.