Pangaea Essay, Research Paper

Since it s early beginnings some 4.6 billion old ages ago, the Earth has been invariably altering its face. Oceans have become comeuppances and what was one time cragged terrain has found itself submerged in salt H2O oceans. Underwater vents make new surfaces daily which one twenty-four hours may host a new species of life. It is this metamorphous nature of the Earth that involvements geologists and paleontologists the universe over. What was the visual aspect of the crude Earth? What changes must hold taken topographic point that resulted in the Earth we know today? These are some of the inquiries that scientists have been turn toing for old ages. There has been much guess about the structural beginnings of the Earth. The most challenging being the thought that at one phase in the Earth s history all the continents were joined together to organize a individual mass of land.

Francis Bacon foremost hypothesized the thought in the 1620 s, concentrating on the parallel shores of South America and Africa. But it wasn t until 1910 when Alfred Wegener scientifically considered the affair of a supercontinent which he called Pangea ( Stokes, 1973 ) . Since this clip, scientists have argued for and against Wegener s account of Pangea. Today sceptics still argue the thought even in the face of overpowering scientific information. Fossil, geologic and paleomagnetic informations clearly validate Wegener s hypothesis- turn outing the being of the ace continent.

Wegener foremost envisioned that the land mass of Pangea split apart and assumed the current Continental places. The drive force behind this brilliant alteration was what Wegener called Continental impetus. As geological grounds to back up the thought of Continental impetus he used the good tantrum of South America and Africa ( Stokes, 1973 ) , which suggests that the two continents used to be joined or were in close propinquity to one another. Oppositions to Continental impetus believed that there was no mechanical mechanism capable of traveling land masss every bit big as continents. The thought of immense organic structures of stone ploughing through the Earth s crust was pathetic. It wasn t until 1960 when Harry H. Hess hypothesized that clefts in the sea floor unfastened along the crest of mid-ocean ridges where new sea floor signifiers and spreads out laterally on either side of the crest. Robert S. Dietz took Hess s thoughts further, calling the procedure sea floor spreading ( which occurs at distributing zones ) and matching it with the thought that old sea floor is absorbed beneath zones of deep ocean trenches and immature mountains ( Briggs, 1987 ) . Dietz s thought of home bases being absorbed into the asthenosphere at subduction zones ( countries of meeting home bases ) answered many inquiries. Since the Earth maintains a changeless size, it merely seems logical that distributing of the crust would be balanced by soaking up of old crust at home base borders.

Sea floor spreading has its ain drive force called convection. Convection occurs in the mantle of the Earth and the procedure involves warming of the mantle from below by the nucleus and loss of heat to the crust in the upper mantle. The hotter slushy liquefied stone of the lower mantle expands and rises towards the crust and is replaced by the colder mantle contents near the surface. The consequence is the round gesture known as convection. It is this round gesture that drives plate motion in either a diverging or meeting mode.

In 1963 and 1973 surveies, J.Tuzo Wilson gave farther acceptance to Dietz s sea floor spreading by detecting that as one moves off from mid-ocean ridges the ages of pelagic islands additions. These and other finds led to the modern position of home base tectonics- the thought that proposes that the Earth s crust is divided into a mosaic of invariably traveling home bases that contain the continents ( Briggs, 1987 ) .

The interruption up Pangea foremost began in the late Triassic, between North Africa and North America. The ensuing rift was thought of as a complete separation of Pangea into Northern and Southern parts termed Laura

sia and Gondwanaland severally. But distribution of tetrapod dodos indicates a north-south connexion that existed until the in-between or late Jurassic ( Briggs, 1987 ) . Other rift formations shortly followed with separation of South America and Africa happening at their southern tips during the early Jurassic. India dividing from Madagascar in the early Cretaceous, and the formation of Continental connexions such as the Bering Land Bridge in the late Cretaceous are a few illustrations of Continental alteration ( Briggs, 1987 ) . The terminal of the Miocene marked a close completion of Continental distributing to current present twenty-four hours places ( Stokes, 1973 ) . Undoubtedly the procedure of home base motion is slow, merely 5cm/ twelvemonth or 1 km/ 20,000 old ages on norm.

Early statements for the being of Pangea were based chiefly on the good tantrum theoretical account that consequences when the continents are pieced together, but scientists and sceptics likewise needed more proof. Over clip, research workers began to patch together scientific informations in order to unlock the secrets of Pangea. Advocates of Pangea used three beginnings of grounds: similar dodo and stone strata found on different continents and paleomagnetic informations. Although non straight linked to the Pangea hypothesis, paleomagnetic information does back up the theory of sea floor distributing which is one of the critical mechanisms of home base ( continent ) motion. In 1963, Fred Vine and Drummond Matthews proposed that as lava erupts at distributing zones and travels laterally off from the zone, it cools. As it cools, the magnetic minerals contained within the lava align with the magnetic field of the Earth. Magnetic readings of the sea floor in these parts gave rise to positive and negative magnetic anomalousnesss matching to stronger and weaker magnetic Fieldss severally ( mention to figure ) . Vine and Matthews concluded that the difference in magnetic field strengths was a consequence of the reversal of the Earth s magnetic field. Stronger readings were a consequence of the magnetic field as we know it today and weaker Fieldss were due to a reversal of this field. Therefore, if an eruption occurred during a period of pole reversal, the magnetic informations would be preserved as a brace of parallel sets in the lava on either side of the distributing zone. This is exactly what scientists observed ( web site ) .

Further support for Pangea comes from cross-sectional surveies of stone strata. Research workers have identified similar beds of Earth in parts of Antarctica, Australia, South America, Africa and India. These nucleus samples display indistinguishable banding consisting of beds of basalt, sandstone/shale, coal and glacial boulder clay ( refer to figure ) . It seems improbable that indistinguishable stone sequences could hold formed independently on separate multitudes of land and at the same clip. It is sensible to reason that these stone forms developed on a individual mass of land that existed early in the history of the Earth ( cyberspace ) .

Of all the grounds proposing the interruption up of Pangea into the continents of today, the most convincing is the figure of works and animate being dodos found in countries of Africa, South America, India and Antarctica. The terminal of the Triassic was marked with significant extinctions among tellurian craniates ( Behrensmeyer et al. ) . Fossils of some of these species have been found on different continents. Wegener proposed that species dispersed when the continents were connected and were so carried to their present places as the continents drifted. Reassembling the continents into Pangea explains the distribution of Glossopteris ( a type of fern ) . Glossopteris dodos have been found in South America, Africa, India and Australia, but when these parts are pieced together, the distribution can be accounted for over a much smaller country ( web ) . The same logical thinking can be applied to dodos of Mesosaurus ( a little fresh water Early Permian reptilian ) found in South Africa and southern Brazil, and to Lystosaurus ( a little mammal like reptilian ) found in parts of Antarctica and Africa ( web ) .