Rodinia, meaning "homeland", is the name of asupercontinent. It had most or all ofEarth's landmass when theNeoproterozoicera began.[1]
Rodinia existed between 1.1billion and 750 million years ago. It formed from parts of an older and poorly understood supercontinent.[2][3]
Rodinia broke up in the first period of the Neoproterozoic, theTonian. Later its continental fragments were re-assembled to formPangaea 300–250 million years ago. In contrast with Pangaea, little is known yet about the exact position and history of Rodinia.
The extreme cooling of the global climate around 700 million years ago (the so-calledSnowball Earth of theCryogenianperiod) and the rapidevolution of primitive life during the followingEdiacaran andCambrian periods may have been caused by the breaking up of Rodinia.
The break-up of Rodinia is understood better than its formation. Extensiveflood basalt flows and volcanic eruptions of Neoproterozoic age are found on most continents. This is evidence for large scalerifting about 750 million years ago.[4] As early as 850 and 800 million years ago,[5] a rift developed, eventually becoming an ocean in theEdiacaran.
In a separate rifting event about 610 million years ago (halfway in the Ediacaran period), theIapetus Ocean formed. It might be that all continental mass was again joined in one supercontinent between roughly 600 and 550 million years ago. This hypothetical supercontinent is calledPannotia.
Unlike later supercontinents, Rodinia itself was entirely barren. It existed before life colonized dry land. It was before theozone layer formed, so Rodinia was too exposed to theultraviolet radiation in sunlight for organisms to live there and leave fossils. However, its existence probably affected the marine life of its time.
In theCryogenian period, the Earth experienced largeglaciations, and temperatures were at least as cool as today. Substantial areas of Rodinia may have been covered byglaciers or the southern polarice cap.
The eventual rifting of the continents created new oceans, andseafloor spreading, which produces warmer, less-dense oceaniclithosphere. Due to its lowerdensity, hot oceanic lithosphere does not lie so deep as old, cool oceanic lithosphere. In periods with relatively large areas of new lithosphere, the ocean floors come up, causing thesea level to rise. The result was a greater number of shallower seas.[4]
The increasedevaporation from the larger water area of the oceans may have increased rainfall, which, in turn, increased theweathering of exposed rock. This increased rainfall may have reducedgreenhouse gas levels. When CO2 level dropped, the period known asSnowball Earth began.[6] Increased volcanic activity also introduced nutrients into the seas. This may have played an important role in the development of the earliest animals.
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