Editing Supercontinent (section)

==Climate==
Continents affect the climate of the planet drastically, with supercontinents having a larger, more prevalent influence. Continents modify global wind patterns, control ocean current paths, and have a higher [[albedo]] than the oceans.<ref name=rogers /> Winds are redirected by mountains, and albedo differences cause shifts in onshore winds. Higher elevation in continental interiors produces a cooler, drier climate, the phenomenon of [[Continental climate|continentality]]. This is seen today in [[Eurasia]], and rock record shows evidence of continentality in the middle of Pangaea.<ref name=rogers />

===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" />

===Precipitation===

Though precipitation rates during [[Monsoon|monsoonal]] circulations are difficult to predict, there is evidence for a large orographic barrier within the interior of Pangaea during the late Paleozoic {{nobr|(~251.9 Ma).}} The possibility of the southwest–northeast trending Appalachian-Hercynian Mountains makes the region's monsoonal circulations potentially relatable to present-day monsoonal circulations surrounding the Tibetan Plateau, which is known to positively influence the magnitude of monsoonal periods within Eurasia. It is therefore somewhat expected that lower topography in other regions of the supercontinent during the [[Jurassic]] would negatively influence precipitation variations. The breakup of supercontinents may have affected local precipitation.<ref name="Baum">Baum, Steven K., and Thomas J. Crowley. "Milankovitch Fluctuations on Supercontinents." Geophysical Research Letters. 19 (1992): 793–796. Print.</ref> When any supercontinent breaks up, there will be an increase in precipitation [[Surface runoff|runoff]] over the surface of the continental landmasses, increasing [[Silicate mineral|silicate]] [[weathering]] and the consumption of CO<sub>2</sub>.<ref name=donnadieu />

===Temperature===

Even though during the Archaean solar radiation was reduced by 30 percent and the [[Cambrian]]-[[Precambrian]] boundary by 6 percent, the Earth has only experienced three [[Ice age|ice ages]] throughout the Precambrian.<ref name=flutaeu /> Erroneous conclusions are more likely to be made when models are limited to one climatic configuration (which is usually present-day).<ref name="baum">Baum, Steven K., and Thomas J. Crowely. "Milankovitch Fluctuations on Supercontinents." Geophysical Research Letters. 19 (1992): 793–796. Print.</ref>

Cold winters in continental interiors are due to rate ratios of radiative cooling (greater) and heat transport from continental rims. To raise winter temperatures within continental interiors, the rate of heat transport must increase to become greater than the rate of radiative cooling. Through climate models, alterations in atmospheric CO<sub>2</sub> content and ocean heat transport are not comparatively effective.<ref name=baum />

CO<sub>2</sub> models suggest that values were low in the late Cenozoic and Carboniferous-Permian glaciations. Although early Paleozoic values are much larger (more than 10 percent higher than that of today). This may be due to high seafloor spreading rates after the breakup of Precambrian supercontinents and the lack of land plants as a [[carbon sink]].<ref name=crowley />

During the late Permian, it is expected that seasonal Pangaean temperatures varied drastically. Subtropic summer temperatures were warmer than that of today by as much as 6–10 degrees, and mid-latitudes in the winter were less than −30 degrees Celsius. These seasonal changes within the supercontinent were influenced by the large size of Pangaea. And, just like today, coastal regions experienced much less variation.<ref name=flutaeu />

During the Jurassic, summer temperatures did not rise above zero degrees Celsius along the northern rim of Laurasia, which was the northernmost part of Pangaea (the southernmost portion of Pangaea was Gondwana). Ice-rafted [[dropstone]]s sourced from Russia are indicators of this northern boundary. The Jurassic is thought to have been approximately 10 degrees Celsius warmer along 90 degrees East [[paleomagnetism|paleolongitude]] compared to the present temperature of today's central Eurasia.<ref name=baum />

===Milankovitch cycles===

Many studies of the [[Milankovitch cycles]] during supercontinent time periods have focused on the mid-Cretaceous. Present amplitudes of Milankovitch cycles over present-day Eurasia may be mirrored in both the southern and northern hemispheres of the supercontinent Pangaea. Climate modeling shows that summer fluctuations varied 14–16 degrees Celsius on Pangaea, which is similar or slightly higher than summer temperatures of Eurasia during the Pleistocene. The largest-amplitude Milankovitch cycles are expected to have been at mid-to high-latitudes during the Triassic and Jurassic.<ref name=baum />

=== Atmospheric gases ===
[[Plate tectonics]] and the chemical composition of the atmosphere (specifically [[greenhouse gas]]es) are the two most prevailing factors present within the geologic time scale. [[Continental drift]] influences both cold and warm climatic episodes. Atmospheric circulation and climate are strongly influenced by the location and formation of continents and supercontinents. Therefore, continental drift influences mean global temperature.<ref name="flutaeu" />

Oxygen levels of the Archaean were negligible, and today they are roughly 21 percent. It is thought that the Earth's oxygen content has risen in stages: six or seven steps that are timed very closely to the development of Earth's supercontinents.<ref name="Campbell">Campbell, Ian H., Charlotte M. Allen. "Formation of Supercontinents Linked to Increases in Atmospheric Oxygen." Nature. 1 (2008): 554–558.</ref>
# Continents collide
# Super-mountains form
# Erosion of super-mountains
# Large quantities of minerals and nutrients wash out to open ocean
# Explosion of marine algae life (partly sourced from noted nutrients)
# Mass amounts of oxygen produced during photosynthesis
The process of Earth's increase in atmospheric oxygen content is theorized to have started with the continent-continent collision of huge landmasses forming supercontinents, and therefore possibly supercontinent mountain ranges (super-mountains). These super-mountains would have eroded, and the mass amounts of nutrients, including [[iron]] and [[phosphorus]], would have washed into oceans, just as is seen happening today. The oceans would then be rich in nutrients essential to photosynthetic organisms, which would then be able to respire mass amounts of oxygen. There is an apparent direct relationship between [[orogeny]] and the atmospheric oxygen content. There is also evidence for increased sedimentation concurrent with the timing of these mass oxygenation events, meaning that the organic carbon and [[pyrite]] at these times were more likely to be buried beneath sediment and therefore unable to react with the free oxygen. This sustained the atmospheric oxygen increases.<ref name="Campbell" />

At {{nobr|2.65 Ga}} there was an increase in [[Isotopes of molybdenum|molybdenum isotope]] fractionation. It was temporary but supports the increase in atmospheric oxygen because molybdenum isotopes require free oxygen to fractionate. Between 2.45 and {{nobr|2.32 Ga,}} the second period of oxygenation occurred, which has been called the 'great oxygenation event.' Evidence supporting this event includes [[red beds]] appearance {{nobr|2.3 Ga}} (meaning that Fe<sup>3+</sup> was being produced and became an important component in soils). 

The third oxygenation stage approximately {{nobr|1.8 Ga}} is indicated by the disappearance of iron formations. [[Neodymium]] isotopic studies suggest that iron formations are usually from continental sources, meaning that dissolved Fe and Fe<sup>2+</sup> had to be transported during continental erosion. A rise in atmospheric oxygen prevents Fe transport, so the lack of iron formations may have been the result of an increase in oxygen. The fourth oxygenation event, roughly {{nobr|0.6 Ga,}} is based on modeled rates of [[Isotopes of sulfur|sulfur isotopes]] from marine carbonate-associated [[sulfate]]s. An increase (near doubled concentration) of sulfur isotopes, which is suggested by these models, would require an increase in the oxygen content of the deep oceans. 

Between 650 and {{nobr|550 Ma}} there were three increases in ocean oxygen levels, this period is the fifth oxygenation stage. One of the reasons indicating this period to be an oxygenation event is the increase in [[redox]]-sensitive [[molybdenum]] in black [[shale]]s. The sixth event occurred between 360 and {{nobr|260 Ma}} and was identified by models suggesting shifts in the balance of <sup>34</sup>S in [[sulfate]]s and <sup>13</sup>C in [[carbonate]]s, which were strongly influenced by an increase in atmospheric oxygen.<ref name="Campbell" /><ref>{{cite web |title=G'day mate: 1.7-billion-year-old chunk of North America found in Australia |url=https://www.MSN.com/en-us/news/technology/day-mate-17-billion-year-old-chunk-of-north-America-found-in-Australia/ar-AAv5aZn |url-status=live |archive-url=https://web.archive.org/web/20180125134510/http://www.msn.com/en-us/news/technology/gday-mate-17-billion-year-old-chunk-of-north-america-found-in-australia/ar-AAv5aZn |archive-date=2018-01-25 |website=www.msn.com}}</ref>