How the theory of plate tectonics changed ideas about the structure of the Earth and continental movement over geological time
The theory of plate tectonics demonstrates the features and movement of Earth’s surface from the past to the present. It offers the illustration that Earth consists of distinct layers with different physical properties, with the Earth’s outer shell divided into several plates. The gigantic cracked plates that floats on the asthenosphere, a layer of semi-liquid rock in the upper mantle, are called tectonic plates. Due to the rocks in the asthenosphere being gooey hot plastic, it is able to change shape and slowly flow from a point to another. In the 20th century, researchers realized that the Earth's crust is not one piece, but is made up of many huge tectonic plates upon which the continents ride. ( livescience.com, 2016 ) |
Originally during 1912, Alfred Wegener, a German meteorologist and geophysicist, claimed that continents were once connected to each other, naming the big landmass Pangaea. He based his theory on a few evidence such as the coastlines of the continents being able to fit together like a jigsaw, species of the same land animals in different continents, and fossils of the same prehistoric plants being found on continents long way apart. However majority of the other scientist disagreed with Wegener’s theory with the reason that there was no mechanism known that could make such huge continents move. But, this is the predecessor to the theory of plate tectonics.
Evidence provided
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Specific examples
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Fossils of the same prehistoric plants / animals can be found on continents long way apart
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Fossils evidence of Glossopteris ( Fern ) spread on a path from South America to Africa to India to Antarctica to Australia
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The coastlines of the continents fits together like a jigsaw
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South America's coastline and Africa's coastline
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Species of the same land animals in different far-apart continents
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East Africa to Madagascar has the same animals
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In 1872, scientists discovered a large mountain ridge in the middle of the Atlantic Ocean that, which was confirmed during 1925, ran the entire length of the Atlantic ocean. Further studies in 1945 till 1953 using sonar demonstrates that the underwater ridge spread into other oceans around Earth, with series of huge cracks along them. This system was later on named the Great Global Rift.
Then, during 1962, Harry Hess, an American geologist, proposed seafloor spreading. Seafloor spreading is the process of new rocky crust being formed at the ocean ridges, spreading outwards. He also explained that crust that’s sinking down into Earth formed ocean trenches, these zones are called subduction zones. This theory was supported by magnetic stripping, the age of the sea floor, and the sediment thickness.
The driving force of tectonics is through the process of convection currents. As the hot magma in the asthenosphere rises up and sinks under again, the friction between it and the tectonic plates causes the plates to move. Gravity also contributes to shifting the plates by slab pull and ridge push. ( NSW Pearson Science 9, 2014 ) ( bbc.co.uk, )
Previously, people had thought that mountains formed when Earth was cooling down and contracted in process, hence making ‘wrinkles’ on the crust. ( visionlearning.com, 2003 ) Our understanding of the Earth had advanced from Wegener’s theory, to further explorations by peer scientists, to Hess’s theory and multiple other supporting investigations that concludes us to the theory of plate tectonics. The theory of the tectonic plates enables to describe all features on earth as though driven by the relative motion of these plates.
Then, during 1962, Harry Hess, an American geologist, proposed seafloor spreading. Seafloor spreading is the process of new rocky crust being formed at the ocean ridges, spreading outwards. He also explained that crust that’s sinking down into Earth formed ocean trenches, these zones are called subduction zones. This theory was supported by magnetic stripping, the age of the sea floor, and the sediment thickness.
The driving force of tectonics is through the process of convection currents. As the hot magma in the asthenosphere rises up and sinks under again, the friction between it and the tectonic plates causes the plates to move. Gravity also contributes to shifting the plates by slab pull and ridge push. ( NSW Pearson Science 9, 2014 ) ( bbc.co.uk, )
Previously, people had thought that mountains formed when Earth was cooling down and contracted in process, hence making ‘wrinkles’ on the crust. ( visionlearning.com, 2003 ) Our understanding of the Earth had advanced from Wegener’s theory, to further explorations by peer scientists, to Hess’s theory and multiple other supporting investigations that concludes us to the theory of plate tectonics. The theory of the tectonic plates enables to describe all features on earth as though driven by the relative motion of these plates.