Continental Drift and Plate Tectonics Essay

Introduction The Beginning of the Continental rank sup invest In the middle of the ordinal atomic number 6, James Hutton proposed a theory, uni figitarianism the present is the disc every channelise to the bypast. It held that processes much(prenominal)(prenominal)(prenominal) as geologic forces- gradual and catastrophic-occurring in the present were the akin that operated in the past. (Matt Rosenberg, 2004) This theory coincides with the theory of Continental bollix that was first proposed by Abraham Ortelius in December 1596, who signaled that sum, southeasterly America, Africa and Eurasia were at one time machine-accessible but had been torn a spark by creationquakes and floods.He also ascertained that the coasts of the eastern calve of southeast America and the Hesperian coasts of Africa fit together like a jigsaw puzzle and this fit becomes peculiarly prominent as the edges of the unblemishedal shelves submit similar shapes and thence, appear to be one time fitted together. (Figure 1.1 and Figure 1.2) The similarity of southern continents geological formations had led Roberto Mantovani to specu latish that every(prenominal) continents had once been a supercontinent and was small in its hoi polloi than it is now. Through volcanic activity, fissures are pretendd in the glow causation this continent to ravish asunder. However, this theory, cognise as the Expanding body politic system has since been proved incorrect.The hypothesis of Continental frameIn 1912, The Theory of Continental cause was intensively developed by Alfred Wegener, who claimed that the field was made up of a single gigantic supercontinent named Pangea since the Permian period, 250 million old age ago. It began forming at the beginning of the Carboniferous period, 365 million days ago, when Gondwana collided into Laurussia producing the Appalachian chaw belt in eastern North America and determination in Paleo-Tethys Ocean and modern landmass became exposed to air. Alexander Du Toit and thence suggested that 145-200 million long time ago, in the middle Jurassic Period, Pangea started breaking up into cardinal small supercontinents, Laurasia in the pairingern hemisphere and Gondwana in the southern hemisphere, with Tethys sea and North Atlantic Ocean separating the two supercontinents.The late Jurassic era began the formation of the crude Mountains and sierra Nevada mountains. In the Cretaceous Period, 65 million eld ago, the two supercontinents then began fragmenting into the present seven continents. (USGS, 2012) The Tethys Sea that lay between the two landmasses was subducted down the stairs Eurasia, forming the lower Atlantic Ocean. Eventually, it disappeared. (Nelson Thomas, 2007) (Figure 2) Wegener proposed that continents were mournful at to the highest degree one yard per centimeury and supported this theory with several(prenominal) points of show up. turn up supporting the Theory of Continental whee l (Alfred Wegener and Du Toit) Alfred Wegener matched up coastlines, and he realized that by fitting the Continental shelves together, cratons organize a contiguous pattern across the confines of second America and Africa. (Lois caravan Wagner, 2013) He realized that mountain ranges that ended at one coastline seemed to begin again on a nonher such(prenominal)(prenominal) as old-fashioned mountains in South Africa that align with the mountains in tightly fitting Buenos Aires in genus Argentina. (Sant, Joseph, 2012) He observe hide outworms of the family Megascolecina, who are unlikely to be long distance migrators, were effectuate in soils of all the Gondwanaland continents. (kangarooistan, 2009) This monovular species could not have arisen on diametric continents without some variations. (WiseGeek, 2010) Fossil remains of a prehistoric reptile cognize as the Mesosaurus had been uncover on some(prenominal) faces of the South Atlantic coasts, yet the creature was uneff ective to swim across the Atlantic Ocean. (Lois Van Wagner, 2013) Fossils of the land reptile, Lystrosaurus were spy in South America, Africa and Antarctica. (Sant, Joseph, 2012).He also discovered the fogey plant Glossopteris was distributed by dint ofout India, South America, southern Africa, Australia and Antarctica. (USGS, 2012)(Figure 3) Alexander Du Toit traveled to Brazil and Argentina where he piece similarities in the fossils and agitate strata to those found in South Africa such as the fossilized remains of Mesosaurus in fresh water deposits, dune deposits lie by basalt flows, tillite and coal beds. Similar layers of carry were make in Antarctica, Australia, South America, Africa and India. (Figure 4) general distribution of Permo-Carboniferous glacial sediments in South America, Africa, Madagascar, Arabia, India, Antarctica and Australia and striations that indicated glacial flow away from the equator and towards the poles were discovered and supported the theor y of Continental Drift which proposed that southern continents were once located over the South Pole region and covered by ice sheets. (Lois Van Wagner, 2013) (Figure 4)He also discovered a foot layer of shale scratched by glaciers and covered by layers of tillite in South Africa, a continent of a tropical equatorial climate. Tillites and varves geological dating back to 2 billion years ago, were found in Canada and India, indicating glaciation on a worldwide shell. Such tillites were found on all major continents except Antarctica, which has been the around extensive glacial continent in earths history. (kangarooistan, 2009) Additionally, fossils of tropical plants in the form of coal deposits were found in Antarctica which implies that Antarctica had to be closer to the Equator. (USGS, 2012) This study of changes in climate taken on the scale of the entire history of reason is known as paleoclimatology. Sediments of rifting have proved the planless apart of Pangea.The riftin g that organize the South Atlantic Ocean began late in the Mesozoic Period when Africa and South America began to except apart. Water from the south then flowed in over time, thus forming the evaporites now found on the coastlines there. (Lois Van Wagner, 2013)(Figure 5) However, Wegener believed that only the continents were moving and they plowed through the rocks of the marine basins. (Colliers Encyclopedia, 1996) Harold Jeffreys then argued that it is impossible for continents to break through red-blooded rock without breaking apart. (USGS, 2012) Wegener also claimed that the centrifugal force of the spinning planet had constrained the continents sideways, gibe to the equator tidal pull from the fair weather and moon had caused lateral livementment. (Sant, Joseph, 2012) His orders of magnitude were similarly weak. Thus, his theory was dismissed. (Lois Van Wagner, 2013) Further instruction and support of the Continental Drift Theory in the 1960s After cosmos War 2, t he U.S. Office of Naval interrogation intensified efforts in ocean-floor mapping, leading to the uncovering of the Mid-Atlantic continue to be part of a continous system of mid- marine ridges on all ocean floors, prompting Harry H. Hess to suggest the theory of sea-floor banquet.The oldest fossils found in ocean sediments were only 180 million years old and little sediment were stack away on the ocean floor. Thus, he suggested that seafloors were no more than a hardly a(prenominal) carbon million years old, significantly jr. than Continental land due to longing magma rising from volcanically dynamical mid- marine ridges, cattle ranch sideways, cooling on the seafloors egress due to cooler temperatures of the sea, solidifying to create new seafloor, thereby pushing the tectonic ordered seriess apart. (Edmond A. Mathez, 2000) The realization that the shape of the Mid-Atlantic ridge and the Atlantic Coast are strikingly similar substantiated the claim that the continents had been get in touched together at the Mid-Atlantic Ridge. (J. Tuzo Wilson, 1996) (Figure 6)The cause of the continental drift that Wegener was unable to explain had been come along researched on by Arthur Holmes who claimed that the driveway of continents was the matter of convection currents driven by the thermal convection in the blistery pants of the interior of the Earth, namely the mantle. The heat source of the mantle comes from radioactivity decomposition in the core. (Figure 7) At rehabilitative abode boundaries, molten basalt flows out on all side of the ridge and cools with the iron particles in the basalt aligning with the earths magnetized field which reverses direction every few hundred thousand years. (Lois Van Wagner, 2013) referable to magma cooling, the coldity of rocks willing be preserve at the time it was organise. (Figure 8.1)In 1950, researchers of paleomagnetism discovered that there were alternating regions of normal and turn magnetic dire ctions symmetrically disposed on both sides of the Mid-Atlantic Ridge magnetic stripping. (J. Tuzo Wilson, 1996) Harry H. Hess theory was thus proven by the magnetic anomalies in the nautical crust. (Nelson Thomas, 2007) (Figure 8.2) It was also discovered that the youngest rocks were closest to the mid-oceanic Ridge and the oldest rocks were near the coasts of the continents. When scientists began collecting magnetic info for North America and Europe, they discovered the north pole seemed to be moving about over time. (ALLA, 2009) However, when data from other continents was put in for the same time frames, it showed different polar locations, thus supporting that continents were moving about.The Theory of household TectonicsThe theory of crustal plate tectonics held that the Earths lithosphere, the Earths crust and the uppermost mantle, is at sea into seven macro-plates and about twelve smaller ones, averaging 50 miles in width. (U.S. Dept. of the Interior, Geological Surve y, 2007) each(prenominal) plate may consist of both oceanic crust and continental crust. (Colliers Encyclopedia, 1996) (Figure 9) It suggests that the ocean floor began to spread at constructive plate boundaries, and continents, existing on plates, travel due to convection currents in the mantle and regular sea-floor spreading. (The Columbia Electronic Encyclopedia, 2011). They drag and move plates preceding(prenominal) them due to rising magma spreading out beneath the earths crust. As two oceanic plates move apart, magma from the under(a)lying asthenosphere mantle wells up from oceanic ridges and becomes rigid enough to join the lithosphere of the plates on either side of the plate boundary, creating new seafloor and eventually, an ocean is receptive up. (J. Tuzo Wilson, 1996) (Figure 10) Examples are the Atlantic Ocean formed between South America and Africa. raw(a) rock is created by volcanism at mid-oceanic ridges and returned to the Earths mantle at oceanic trenches wher e the boneheadedr plate is subducted under the other, forcing the earths crust back into the mantle. (J. Tuzo Wilson, 1996) This process is known as the ridge push and slab-pull. (Figure 11) diametrical plate tectonics question and subsequent tectonic activities Transform plate movement causing earthquakes Seismic waves disrupting the continents in the form of earthquakes are due to the great add of stress and energy built up by the friction of the moving plates, peculiarly during transform plate movement, where plates slide past each other in a grinding, shearing manner and form turn faults (Columbia Electronic Encyclopedia, 2011). (Figure 12.1) There is gradual divagation of rocks before the ductile limit of rocks is exceeded, causing the plates to lock and the fault to break, leading to fulminant release of stored energy, causing earthquakes. (Nelson Thomas, 2007)An example is the strike-slip fault, San Andreas shift key in California. (Figure 12.2) (WiseGeek, 2010) Ocea nic and Oceanic focused plate movement Other evidence of plate tectonics movement are most of the worlds active outletes located along or near the boundaries between shifting plates known as plate-boundary volcanoes. (J. Tuzo Wilson, 1996) When two oceanic plates collided, the denser plate will subduct under the other, forming a deep oceanic trench and form magma through hydration or decompression melting. The magma organism less dense than the surrounding mantle, rises and escapes to the sea-floor through cracks in the earths crust, forming submarine volcanoes that rise to a higher place water to form a mountain range of volcanic islands known as island arcs, such as the Japan Islands. (Figure 13) Examples would be the pacific Plate subducting underneath the North American Plate creating the Kuril oceanic abyss and the Japan Trench that can be found along the Pacific Ring of Fire.Many volcanoes such as Mount St. Helens, Mount fuji in Japan and Mount Pinatubo in the Phillipin es are located along the circuit of the Pacific Ocean Basin where boundaries of several plates such as the Nazca and the Cocos Plate are found, forming the Ring of Fire. (Fraser Cain, 2009) (Figure 14) Volcanoes formed not due to tectonic activities 5 per cent of the worlds volcanoes are formed at isolated hot sight and many intra-plate volcanoes form roughly one-dimensional set ups along the middle of oceanic plates. (The Columbia Electronic Encyclopedia, 2011)Examples are the Yellowstone internal park and Hawaiian Islands, an intra-plate volcanic chain developed by the Pacific plate passing over a deep, nonmoving hot spot, located 60 km beneath the present-day position of the Island of Hawaii. Heat from this hotspot produced a changeless source of basaltic magma by partly melting the overriding Pacific Plate.This magma rises through the mantle to erupt onto the seafloor, forming an active seamount. all over time, countless eruptions caused the seamount to grow until it fi nally emerges above sea level to form island volcanoes. The move plate movement eventually carries the island volcano away from the hotspot, cutting it off from the hot spot and creating another island volcano. This cycle is repeated, forming the Hawaiian Islands. (U.S. Dept. of the Interior, Geological Survey, 2007) (Figure 15) Continental and Continental confluent plate movement Continental shut up mountain ranges are evidence of two continental plates that are thick and smiling thus, preventing both plates from subducting. Instead, the two plates collide into each other forming fold mountain ranges in a process known as orogenesis.An example is the high elevation of the Tibetan plateau, fringed to the south by the Himalayas as the edges of the Indian and Eurasia plate buckle, excite, fold and deform. Mt. Everest is the highest teetotum on Earth, yet Yellowband limestone that was originally part of the shallow seals of the Tethys Ocean was found on Mount Everest at a height of 8462m. (Figure 16) Oceanic and Continental oblique plate movement Mountains are formed when oceanic crust is subducted under a continental crust, resulting in melting of rock, thus volcanic activity and causing the continental crust to deform, rise and buckle upwards under compressional forces.Examples are the Andes Mountain, the Chile-Peru Trench and the uplift of the Rockies and Appalachians in the past. (The Columbia Electronic Encyclopedia, 2007) The disconcert Mountains was formed approximately 250 million years ago, due to the Pacific plate subducting under the North American plate, (Mary Ann Resendes, 2012) thus creating the Sierra Nevada foothills, subsequently creating the Cape of Good try for as the ocean erodes the soft sandstone of carry over Mountains on the coast. (National Geographic, 1996)Other tectonic activities such as the Wadati-Benioff zones, that are earthquake zones parallel to oceanic trenches are also formed at such subduction zones and inclined from 40 to 60 degrees from the horizontal, ex lean several hundred kilometres into the mantle. (Figure 17) Continental and Continental divergent plate movement When two continental crusts are pulled apart due to tensional forces, the area descends and forms a rift valley and sea such as the East African breakout vale and the Red Sea that runs from the Jordan Valley and into East Africa, already dotted with volcanoes such as Hermon. This is due to the area being stretched, causing the crustal material to thin, weaken and sink due to lowered density. (Figure 18)IsostasyAlso, isostasy takes place wherever a large amount of weight down such as the fold mountain ranges created from plate tectonics movements is formed or glaciers, pushes down the Earths crust and creates a small dent. Isostasy also takes place at divergent plate boundaries when a large amount of weight is outside from an area, causing that portion of the Earths crust to rise. Therefore, equilibrium in the earths crust is achieved such that forces elevating landmasses balances those tending to depress landmasses. (Learning Network, 1998) (Figure 19)