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Encyclopedia > Rodinia

In geology, Rodinia (from the Russian родина, or "motherland") refers to one of the oldest known supercontinents, which contained most or all of Earth's then-current landmass. Paleomagnetic evidence provides clues to the paleolatitude of individual formations, but not to their longitude, which geologists have pieced together by comparing similar strata, often now widely dispersed. This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... In geology, a supercontinent is a land mass comprising more than one continental core, or craton. ... Paleomagnetism refers to the study of the record of the Earths magnetic field preserved in various magnetic minerals through time. ...

Contents

Lifetime

Geologic evidence suggests that Rodinia formed and broke apart in the Neoproterozoic, probably existing as a single continent from 1 billion years ago until it began to rift into eight smaller continents about 800 million years ago.[1] It is thought to have been largely responsible for the cold climate of the Neoproterozoic era. The Neoproterozoic Era is the unit of geologic time from 1,000 to 542 +/- 0. ... One computer simulation of conditions during the Snowball Earth period. ...


Formation

Rodinia began forming about 1.3 billion years ago from three or four pre-existing continents, an event known as the Grenville orogeny.[2] The absence of fossils of hard-shelled organisms and reliable paleomagnetic data make the movements of continents earlier in the Precambrian, prior to this event, uncertain. (See Columbia for one possible reconstruction of an earlier supercontinent.) The Grenville orogeny was an episode of mountain-building (orogeny) associated with the assembly of the ancient supercontinent Rodinia. ... Paleomagnetism refers to the study of the record of the Earths magnetic field preserved in various magnetic minerals through time. ... The Precambrian (Pre-Cambrian) is an informal name for the supereon comprising the eons of the geologic timescale that came before the current Phanerozoic eon. ...


The arrangement of Rodinia has been hypothesized using paleomagnetic data from the Seychelles islands and India and the Grenville mountain belts, which were formed by the Grenville orogeny and span multiple modern continents, as references.[1][2]


Although the details are disputed by paleogeographers, the continental cratons that formed Rodinia appear to have clustered around Laurentia (proto-North America), which constituted Rodinia's core. Palaeogeography is the study of the ancient geography of the Earths surface. ... World geologic provinces. ... This article or section does not adequately cite its references or sources. ... North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ...


It appears that the east coast of Laurentia lay adjacent to the west coast of South America, while a conjoined Australia and Antarctica seem to have lain against the proto-North American west coast. A third craton, what would become north-central Africa, was caught in between these two colliding masses.[3]. South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... A world map showing the continent of Africa Africa is the worlds second-largest and second most-populous continent, after Asia. ...


Other cratons such as the Kalahari (southern Africa), the Congo (west-central Africa), and the San Francisco (southeastern South America), appear to have been separate from the rest of Rodinia.


Paleogeography

Rodinia's landmass was probably centered south of the equator.[4] Because Earth was at that time experiencing the Cryogenian period of glaciation, and temperatures were at least as cool as today, substantial areas of Rodinia may have been covered by glaciers or the southern polar ice cap. The interior of the continent, being so distant from the temperature-moderating effects of the ocean, was probably seasonally extremely cold (see continental climate). It was surrounded by the superocean geologists are calling Mirovia (from mir, the Russian word for "globe"). World map showing the equator in red In tourist areas, the equator is often marked on the sides of roads The equator marked as it crosses Ilhéu das Rolas, in São Tomé and Príncipe. ... The Cryogenian Period (from Greek cryos ice and genesis birth) is the second geologic period of the Neoproterozoic Era, followed by the Ediacaran Period. ... A glaciation (a created composite term meaning Glacial Period, referring to the Period or Era of, as well as the process of High Glacial Activity), often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator. ... This article is about the geological formation. ... This does not cite any references or sources. ... Regions containing a continental climate exist in portions of Northern Hemisphere continents, and also at higher elevations in certain other parts of the world. ... The supercontinent Pangaea surrounded by the superocean Panthalassa. ... Mirovia (from Russian мировой, mirovoy, meaning global) was a global ocean that encompassed the supercontinent Rodinia in the Neoproterozoic era, about 1 billion to 750 million years ago. ... For other uses, see Mir (disambiguation). ...


Cold temperatures may have been exaggerated during the early stages of continental rifting. Geothermal heating peaks in crust about to be rifted; and since warmer rocks are less dense, the crustal rocks rise up relative to their surroundings. This rising creates areas of higher altitude, where the air is cooler and ice is less likely to melt with changes in season, and it may explain the evidence of abundant glaciation in the Ediacaran period.[5] Geothermal heating is a method of heating and cooling a building. ... For other uses, see Density (disambiguation). ... The Ediacaran[5][6]  â€¢  â€¢  | Neoproterozoic (last æon of the Precambrian) Phanerozoic Axis scale: millions of years ago. ...


The eventual rifting of the continents created new oceans, and seafloor spreading, which produces warmer less-dense rock, probably increased sea level by displacing ocean water. The result was a greater number of shallower oceans. Age of oceanic crust. ...


The evaporation from these oceans may have increased rainfall, which, in turn, increased the weathering of exposed rock. By inputting δ18O data into computer models, it has been shown that in conjunction with quick-weathering volcanic rock, this increased rainfall may have reduced greenhouse gas levels to below the threshold required to trigger the period of extreme glaciation known as Snowball Earth.[6] “Vaporization” redirects here. ... In paleoclimatology and paleooceanography δ18O is the ratio of stable isotopes 18O:16O. It is commonly used through foraminifera data to model temperature. ... Ignimbrite is a deposit of a pyroclastic flow. ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ... One computer simulation of conditions during the Snowball Earth period. ...


All of this tectonic activity also introduced into the marine environment biologically important nutrients, which may have played an important role in the development of the earliest animals. The tectonic plates of the world were mapped in the second half of the 20th century. ...


Separation

In contrast to Rodinia's formation, the movements of continental masses during and since its breakup are fairly well understood. Evidence of extensive lava flows and volcanic eruptions around the Precambrian-Cambrian boundary, especially in North America, suggest that Rodinia began to rift apart no later than 750 million years ago.[5] Other continents, including Baltica and Amazonia, rifted off Laurentia 600 to 550 million years ago, opening the Iapetus Ocean between them. The separation also led to the birth of Panthalassic Ocean (or Paleo-Pacific).[1] The Precambrian (Pre-Cambrian) is an informal name for the supereon comprising the eons of the geologic timescale that came before the current Phanerozoic eon. ... For other uses, see Cambrian (disambiguation). ... Baltica (green) Baltica is a Late Proterozoic-Early Palaeozoic continent that now includes the East European craton of northwestern Eurasia. ... The Iapetus Ocean was an Ocean that existed in the Southern Hemisphere between Scotland, England and Scandinavia between 400 and 600 million years ago. ... The blue ocean surrounding Pangaea is Panthalassa Panthalassa (Greek for all seas) was the vast ocean that surrounded the supercontinent Pangaea during the late Paleozoic era and the early Mesozoic era. ...


The eight continents that made up Rodinia later re-assembled into another global supercontinent called Pannotia and, after that, once more as Pangaea. Pannotia is the name given to a hypothetical supercontinent that existed from about 600 to about 540 mya. ... For other uses, see Pangaea (disambiguation). ...


See also

The supercontinent cycle describes the quasi-periodic aggregration and dispersal of Earths continental crust. ...

External links

References

  1. ^ a b c Torsvik, Trond H (May 2003). "The Rodinia jigsaw puzzle". Science 300 (5624): 1379. 
  2. ^ a b Rodinia. Retrieved on 2006-03-10.
  3. ^ Scotese, Christopher R.. More Information About the Late Precambrian. Paleomap Project. Retrieved on 2006-03-10.
  4. ^ Rodinia. Palaeos. Retrieved on 2006-03-10.
  5. ^ a b McMenamin, Mark A.; Dianna L. McMenamin [1990-01-15]. "The Rifting of Rodina", The Emergence of Animals. ISBN 0-231-06647-3. 
  6. ^ Donnadieu, Yannick; Yves Goddéris, Gilles Ramstein, Anne Nédélec, Joseph Meert (March 2004). "A 'snowball Earth' climate triggered by continental break-up through changes in runoff". Nature 428: 303-306. doi:10.1038/nature02408. 

  Results from FactBites:
 
Rodinia - definition of Rodinia in Encyclopedia (170 words)
In geology, Rodinia is used to refer to a supercontinent that both formed and broke up in the Neoproterozoic.
Rodinia is thought to have formed about 1000 million years ago and to have embodied most or all of Earth's existing continental crust.
Rodinia is a Bulgarian (Rodina) and Russian word meaning "homeland", which is used in various contexts.
Rodinia (121 words)
In Geology, Rodinia is used to refer to a 'supercontinent' that formed and broke up in the Neoproterozoic.
Rodinia is thought to have formed about 1000 million years ago and to have embodied most or all of the Earth's continents.
Rodinia is thought to have broken up into eight continents around 600 million years ago.
  More results at FactBites »


 

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