Rodinia

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In geology, Rodinia (from Russian, "homeland") refers to one of the oldest-known supercontinents, which contained most or all of Earth's current landmass. Rodinia both formed and rifted apart in the Neoproterozoic, existing as a single continent from 1 billion years ago until it began to break apart into eight smaller continents about 750 million years ago. It was surrounded by the superocean Mirovia.

1 Formation
2 Paleogeography
3 Separation
4 See also
5 External links
6 References

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Formation

Rodinia began forming about 1.3 billion years ago from three or four pre-existing continents, an event known as the Grenville orogeny.<ref name="peripatus">Template:Cite web</ref> 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.

The arrangement of Rodinia has been hypothesized primarily using paleomagnetism and the Grenville mountain belts, which were formed by the Grenville orogeny and span multiple modern continents, as references.<ref name="peripatus" /> Although the details are disputed by among paleogeographers, the continental cratons 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">Template:Cite web</ref>

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Paleogeography

Rodinia's landmass was probably centered south of the equator.<ref>Template:Cite web</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 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 extremely cold at times.

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.<ref name="mcmenamin">Template:Cite book</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. 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.

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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.<ref name="mcmenamin" /> The eight continents that made up Rodinia later re-assembled into another global supercontinent called Pannotia and, after that, once more as Pangaea.

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