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. According to the first model for Precambrian supercontinents described above the breakup of Kenorland and Rodinia was associated with the Paleoproterozoic and Neoproterozoic glacial-epochs, respectively. In contrast, the second solution described above 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. 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. 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 CO2 levels to occur at the same time. 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 early Silurian through the late Mississippian 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 coast. Precipitation Though precipitation rates during monsoonal circulations are difficult to predict, there is evidence for a large orographic barrier within the interior of Pangaea during the late Paleozoic The possibility of the SW-NE 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. When any supercontinent breaks up, there will be an increase in precipitation runoff over the surface of the continental landmasses, increasing silicate weathering and the consumption of CO2. Temperature Even though during