Rodinia: Perbedaan revisi

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Nama Rodinia sendiri dipopulerkan oleh Dalziel (1991), Moores (1991) dan Hoffman (1991). Rodinia adalah kata dalam [[bahasa Rusia]] yang berarti “motherland” (tanah ibu/leluhur). Konon, Rodinia mulai terbentuk sekitar 1400 juta tahun yang lalu (Ma), pada saat 3 sampai 4 benua mulai menyatu. Konon lagi, pada sekitar 1000 Ma Rodinia ini sudah jelas terkonsolidasi, yang ditunjukkan oleh pembentukan sebuah rangkaian pegunungan. Para ahli menyebut proses pembentukan rangkaian [[pegunungan]] itu dengan nama Grenville Orogeny.
 
Istilah [[Grenville Orogeny]] diambil dari sebuah komplek [[batuan metamorf]] terdeformasi yang ditemukan di kota [[Grenville]], [[Quebec]], [[Kanada]]. Grenville Province, demikian nama geologi komplek [[batuan metamorf]] itu,
tersebar memanjang sampai ke wilayah Texas sekarang. Batuan Grenville Province didominasi oleh Gneiss dan dipercaya juga berada di Brazil bagian barat, menjadi bagian dari kraton Amazonia (Tohver et al.,
2002), tapi diberi nama lain oleh para ahli geologi, Formasi Nova Floresta.
 
==Lifetime==
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Geologic evidence suggests that Rodinia terbentuk 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 juta tahun yang lalu.<ref name="science">{{cite journal | last = Torsvik | first = Trond H | year = 2003 | month = May | title = The Rodinia jigsaw puzzle | journal = Science | volume = 300 | issue = 5624 | pages = 1379 | doi = 10.1126/science.1083469 | pmid = 12775828}}</ref> It is thought to have been largely responsible for the [[Snowball Earth|cold climate of the Neoproterozoic era]].
 
Rodinia is thought to have been preceeded by the [[Vaalbara]] supercontinent and succeeded by the [[Pangaea]] supercontinent, with intervening periods when several continents existed.
 
== Formasi ==
Rodinia terbentuk sekitar 1.3 miliar tahun lalu dari tiga atau empat [[benua]].
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Rodinia terbentuk sekitar 1.3 miliar tahun lalu dari tiga atau empat [[benua]], an event known as the [[Grenville orogeny]].<ref name="peripatus">{{cite web | url = http://www.peripatus.gen.nz/Paleontology/Rodinia.html | title = Rodinia | accessdate = 2006-03-10}}</ref> The absence of fossils of hard-shelled organisms and reliable [[paleomagnetism|paleomagnetic]] data make the movements of continents earlier in the [[Precambrian]], prior to this event, uncertain. (See [[Columbia (supercontinent)]] for one possible reconstruction of an earlier supercontinent.)
 
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.<ref name="science" /><ref name="peripatus" />
 
Although the details are disputed by [[paleogeography|paleogeographers]], the continental [[craton]]s that formed Rodinia appear to have clustered around [[Laurentia]] (proto-[[North America]]), which constituted Rodinia's core.
 
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.<ref name="scotese">{{cite web | url = http://www.scotese.com/info.htm | last = Scotese | first = Christopher R. | title = More Information About the Late Precambrian | work = Paleomap Project | accessdate = 2006-03-10}}</ref>.
 
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.
 
==Paleogeografi==
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Rodinia's landmass was probably centered selatan of the [[ekuator]].<ref>{{cite web | url = http://www.palaeos.com/Earth/Geography/Rodinia.htm | title = Rodinia | publisher = Palaeos | accessdate = 2006-03-10}}</ref> 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 [[glacier]]s 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").
 
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 [[Density|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.<ref name="mcmenamin">{{cite book | last = McMenamin | first = Mark A. | coauthors = Dianna L. McMenamin | title = The Emergence of Animals | origdate = 1990-01-15 | id = ISBN 0-231-06647-3 | chapter = The Rifting of Rodina}}</ref>
 
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.
 
The [[evaporation]] from these oceans may have increased rainfall, which, in turn, increased the weathering of exposed rock. By inputting data on [[Δ18O|the ratio of stable isotopes <sup>18</sup>O:<sup>16</sup>O]] into computer models, it has been shown that in conjunction with quick-weathering of [[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]].<ref>{{cite journal | last = Donnadieu | first = Yannick | coauthors = Yves Goddéris, Gilles Ramstein, Anne Nédélec, Joseph Meert | year = 2004 | month = March | title = A 'snowball Earth' climate triggered by continental break-up through changes in runoff | journal = Nature | volume = 428 | pages = 303–306 | doi = 10.1038/nature02408}}</ref>
 
All of this [[Plate tectonics|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.
 
== Lihat pula ==
== Pranala luar ==
* {{en}} [http://www.scotese.com/Rodinia3.htm Return to Precambrian]
* {{id}} [http://geoblogi.wordpress.com/2008/03/11/rodinia-pangaea-laurasia-dan-gondwana-bagian-1/ Rodinia]
 
[[Kategori:Geologi]]
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