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Tectonic Plates

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Elizabeth Miller

on 3 February 2013

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Transcript of Tectonic Plates

Concept Map Joy Wall and Elizabeth Miller Plate Tectonics Continental Drift Sea Floor Spreading Continental Drift is a theory developed by Alfred Wegener of how the continents used to fit together prior to their positions today. It explains that the Earth used to have one super continent, Pangea, that broke apart into separate continents. Sea Floor Spreading was a theory developed and later proven by Harry Hess during World War II. It states that the ocean floor was expanding through subduction, in which Earth recycles crust. He claimed that lava was coming up from underwater volcanoes and creating new rock, making the sea floor grow. The earth didn't grow, however, because the tectonic plates, or pieces of Earth's crust, were being pushed under one another as new land was being formed. Therefore, the old land was melted, and the Earth would in turn never grow. Problems Alfred Wegener was in a convention when he presented his theory. The people of the convention refused to believe that the continents could move, and he was booed out of the convention. The main issue with his theory was that he could not explain how it had happened, making it very difficult to convince the already doubtful people. Continental Drift To see an animation:
http://www.scotese.com/pangeanim.htm Evidences Process of Discovery Harry Hess discovered the Mid-Atlantic Ridge, a mountain range on the sea floor, while using sonar for navy-related purposes during World War II. Upon further investigation, he found that the rock progressively got older as he traveled farther from the Mid-Atlantic Ridge. Evidences He used core samples of rock from the ocean floor to prove the age of the rock increased with the distance from the Mid-Atlantic Ridge. His discovery supported the theory of Continental Drift because it explained that the continents, or tectonic plates, moved as a result of the ocean floor expanding, which pushed the continents in different directions. Reverse Polarity Another part of Harry Hess' discovery was that the rock had rifts in opposite directions. His find showed that Earth's magnetism had shifted throughout history, a process called reverse polarity, or reverse magnetism. Pictures Shapes of the continents and how they would fit together
Folded mountains
Glacial deposits in warm areas
Coal deposits
Fossils of plants and animals Demonstration An animation of how Continental Drift and Sea Floor Spreading are connected:
http://www.scotese.com/sfsanim.htm To see an animation of Reverse Polarity:
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