<P> Besides having compositional effects on the upper mantle by replenishing the large - ion lithophile elements, volcanism affects the plate movement . The plates will be moved towards a geoidal low perhaps where the slab avalanche occurred and pushed away from the geoidal high that can be caused by the plumes or superplumes . This causes the continents to push together to form supercontinents and was evidently the process that operated to cause the early continental crust to aggregate into Protopangea . Dispersal of supercontinents is caused by the accumulation of heat underneath the crust due to the rising of very large convection cells or plumes, and a massive heat release resulted in the final break - up of Paleopangea . Accretion occurs over geoidal lows that can be caused by avalanche slabs or the downgoing limbs of convection cells . Evidence of the accretion and dispersion of supercontinents is seen in the geological rock record . </P> <P> The influence of known volcanic eruptions does not compare to that of flood basalts . The timing of flood basalts has corresponded with large - scale continental break - up . However, due to a lack of data on the time required to produce flood basalts, the climatic impact is difficult to quantify . The timing of a single lava flow is also undetermined . These are important factors on how flood basalts influenced paleoclimate . </P> <P> Global paleogeography and plate interactions as far back as Pangaea are relatively well understood today . However, the evidence becomes more sparse further back in geologic history . Marine magnetic anomalies, passive margin match - ups, geologic interpretation of orogenic belts, paleomagnetism, paleobiogeography of fossils, and distribution of climatically sensitive strata are all methods to obtain evidence for continent locality and indicators of environment throughout time . </P> <P> Phanerozoic (541 Ma to present) and Precambrian (4.6 Ga to 541 Ma) had primarily passive margins and detrital zircons (and orogenic granites), whereas the tenure of Pangaea contained few . Matching edges of continents are where passive margins form . The edges of these continents may rift . At this point, seafloor spreading becomes the driving force . Passive margins are therefore born during the break - up of supercontinents and die during supercontinent assembly . Pangaea's supercontinent cycle is a good example for the efficiency of using the presence, or lack of, these entities to record the development, tenure, and break - up of supercontinents . There is a sharp decrease in passive margins between 500 and 350 Ma during the timing of Pangaea's assembly . The tenure of Pangaea is marked by a low number of passive margins during 336 to 275 Ma, and its break - up is indicated accurately by an increase in passive margins . </P>

Which of the following is the name of the ancient supercontinent formed 28 million years ago