Editing Supercontinent (section)

===Glacial===

The term glacial-epoch refers to a long episode of [[Glacial period|glaciation]] on Earth over millions of years.<ref name='eyles'>Eyles, Nick. "Glacio-epochs and the Supercontinent Cycle after ~3.0 Ga: Tectonic Boundary Conditions for Glaciation." Paleogeography, Palaeoclimatology, Palaeoecology 258 (2008): 89–129. Print.</ref> Glaciers have major implications on the climate, particularly through [[sea level change]]. Changes in the position and elevation of the continents, the paleolatitude and ocean circulation affect the glacial epochs. There is an association between the rifting and breakup of continents and supercontinents and glacial epochs.<ref name=eyles /> According to the model for Precambrian supercontinent series, the breakup of Kenorland and Rodinia was associated with the [[Paleoproterozoic]] and [[Neoproterozoic]] glacial epochs, respectively. 

In contrast, the Protopangea–Paleopangea theory shows that these glaciations correlated with periods of low continental velocity, and it is concluded that a fall in tectonic and corresponding volcanic activity was responsible for these intervals of global frigidity.<ref name="piper2" /> During the accumulation of supercontinents with times of regional uplift, glacial epochs seem to be rare with little supporting evidence. However, the lack of evidence does not allow for the conclusion that glacial epochs are not associated with the collisional assembly of supercontinents.<ref name="eyles" /> This could just represent a [[preservation bias]].

During the late [[Ordovician]] (~458.4 Ma), the particular configuration of Gondwana may have allowed for glaciation and high CO<sub>2</sub> levels to occur at the same time.<ref name="crowley">Crowley, Thomas J., "Climate Change on Tectonic Time Scales". Tectonophysics. 222 (1993): 277–294.</ref> However, some geologists disagree and think that there was a temperature increase at this time. This increase may have been strongly influenced by the movement of Gondwana across the South Pole, which may have prevented lengthy snow accumulation. Although late Ordovician temperatures at the South Pole may have reached freezing, there were no ice sheets during the [[Llandovery epoch|early Silurian]] {{nobr|(~443.8 Ma)}} through the late [[Mississippian age|Mississippian]] {{nobr|(~330.9 Ma).}}<ref name="flutaeu" /> Agreement can be met with the theory that continental snow can occur when the edge of a continent is near the pole. Therefore Gondwana, although located tangent to the South Pole, may have experienced glaciation along its coasts.<ref name="crowley" />