Supercontinent cycle
The most recent supercontinent, Pangaea, formed about 300 million years ago (0.3 Ga), during the Paleozoic era.
This change is thought to have come about as subduction and continental collision introduced eclogite into subcontinental diamond-forming fluids.
[3] The hypothesized supercontinent cycle is concurrent with the shorter-term Wilson Cycle named after plate tectonics pioneer John Tuzo Wilson, which describes the periodic opening and closing of oceanic basins from a single plate rift.
The oldest seafloor material found today dates to 170 Ma, whereas the oldest continental crust material found today dates to 4 Ga, showing the relative brevity of the regional Wilson cycles compared to the whole-planetary pulses seen in the arrangement of the continents.
The second view, based on both palaeomagnetic and geological evidence, is that supercontinent cycles did not occur before about 0.6 Ga (during the Ediacaran period).
This reconstruction[4] is based on the observation that if only small peripheral modifications are made to the primary reconstruction, the data show that the palaeomagnetic poles converged to quasi-static positions for long intervals between about 2.7–2.2 Ga; 1.5–1.25 Ga; and 0.75–0.6 Ga.[5] During the intervening periods, the poles appear to have conformed to a unified apparent polar wander path.
The paleomagnetic data are adequately explained by the existence of a single Protopangea–Paleopangea supercontinent with prolonged quasi-integrity.
Major influences on sea level during the break up of supercontinents include: oceanic crust age, lost back-arc basins, marine sediment depths, emplacement of large igneous provinces, and the effect of passive margin extension.
Of these, oceanic crust age, and marine sediment depths seem to play some of the largest roles in creating a sea level model.
where κ is the thermal diffusivity of the mantle lithosphere (c. 8×10−7 m2/s), aeff is the effective thermal expansion coefficient for rock (c. 5.7×10−5 °C−1), T1 is the temperature of ascending magma compared to the temperature at the upper boundary (c. 1220 °C for the Atlantic and Indian Oceans, c. 1120 °C for the eastern Pacific) and dr is the depth of the ridge below the ocean surface.
Because the continental shelf has a very low slope, a small increase in sea level will result in a large change in the percent of continents flooded.
If the world ocean on average is young, the seafloor will be relatively shallow, and sea level will be high: more of the continents are flooded.
If the world ocean is on average old, seafloor will be relatively deep, and sea level will be low: more of the continents will be exposed.
[11] As genetic drift occurs more frequently in small populations, diversity is an observed consequence of geographic isolation.
In late Neoproterozoic to early Paleozoic, when the tremendous proliferation of diverse metazoa occurred, isolation of marine environments resulted from the breakup of Pannotia.
