Plate Tectonics Essay Example | Topics and Well Written Essays - 750 words

Plate Tectonics - Essay Example This paper explores both Wegener's theory and Plate Tectonic Theory, explaining how the Earth's land masses move and the construction and destruction of the Earth's crust and the features of plate tectonics as understood today. Plate Tectonics In 1911, Alfred Wegener (1880-1930), a German geophysicist, was intrigued to explain similarities in fossils of plants and animals found on either side of the Atlantic . Scientific thinking of the time was that continents were joined by land bridges that were now submerged by the ocean. However, Wegener also noticed the similar shapes of the coastlines of the continents and similar geology that supported his theory of continental drift. He postulated that these land masses may have been joined together at one time and that the original land mass, called ‘Pangaea’ (after the Greek for ‘all of the Earth’) has broken up and drifted apart . Wegener found evidence to support his theory of continental drift. He noticed that land masses fitted together with adjacent land masses. He also found signs of glaciation on the plains of Africa and coal deposits, usually associated with tropical areas, found near the North Pole. He also found fossils of exactly the same prehistoric species located in the same areas if the land masses were joined together, see Figure 1. . Figure 1: Locations of spread of fossils across continents before they broke up . Wegener did not fully explain what caused continental drift. He suggested two hypotheses, one that continents moved due to the forces associated with the rotation of the Earth and a second, which suggested continents moved due to tidal attraction of the Sun and Moon . However, both of these forces were too weak. These hypotheses were ridiculed by other scientists because no answer could be provided to explain how continental masses move . The original theory of continental drift was discredited, helped along by the growing anti-German feeling in the 1910s and 1920s and Wegener’s lack of scientific knowledge of geology . Wegener’s principle of continental drift was discredited but it did pave the way for scientists to explore why parts of the Earth’s surface have moved over time . Paleomagnetic studies, which measured the Earth's past magnetic field, found that the magnetic North Pole seemed to wander around the Earth over time . Evidence from seismometers, originally installed to monitor nuclear testing by the 1960s, found that geological phenomenon, such as volcanoes and earthquakes, were mostly found along the edges of tectonic plates . In addition, scientists found that rock crystals in certain rocks varied from normal to reversed polarity depending on when the rock was formed and solidified . These patterns mirrored themselves either side of the mid-oceanic ridge in the middle of ocean basins and rock samples were older the farther from the mid-oceanic ridge . All this evidence answered the problem Wegener was unable to; that solid continental and oceanic plates of the Earth’s crust, or lithosphere, ‘float’ on molten viscous rock called the asthenosphere, which forms the basis of Plate Tectonics Theory . Based on the Plate Tectonics Theory, plates adjacent to one another must move. Plates can move apart (forming a divergence plate boundary), together (forming a convergent plate boundary) or slide or grate against each other (creating a transform fault boundary) . A diverging plate