Earth 120, Week 7 Note
Earth 120, Week 7 Note ERTH 120
Santa Ana College
Popular in Phys Earth/Space Systems
Popular in Earth Science
This 2 page Class Notes was uploaded by alicekhanh on Wednesday March 30, 2016. The Class Notes belongs to ERTH 120 at Santa Ana College taught by Joanna Fantozzi in Spring 2016. Since its upload, it has received 42 views. For similar materials see Phys Earth/Space Systems in Earth Science at Santa Ana College.
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Date Created: 03/30/16
Chapter 7: Plate Tectonics 1. Earth’s Interior - Earth’s interior consists of three main layers based on composition Crust - rich in silicon and oxygen (aka silicates) Continental crust - thicker, less dense Oceanic crust - thinner, more dense Mantle - contains more iron and magnesium More dense than both types of crust Core - mostly iron and nickel Outer - liquid iron o Generates magnetic field, which sometimes flip-flops Inner - solid iron and nickel o High pressures keep it in the solid form - Earth’s interior consists of two main layers based on properties Lithosphere Behaves rigidly Crust and upper mantle Asthenosphere Flows as a soft solid Upper mantle 2. Evidence for Plate Tectonics - Alfred Wegener compiled evidence for continental drift based on: Fit of the continents Identical fossils found on land separated by the sea Similar geologic features found on land separated by the sea Evidence of past glaciers found on land now far from the poles - But the hypothesis of continental drift was not accepted since it could not explain how or why continents moved - Harry Hess later proposed the theory of sea-floor spreading A chain of underwater volcanoes exists in the middle of the ocean (known as mid-ocean ridges) As continents drift apart, new ocean floor forms in between as lava cools at the mid-ocean ridges and pushes the plates apart Evidence is seen in the magnetic stripes in the sea floor As new ocean floor forms, the iron-rich minerals inside align with the magnetic field But sometimes, the Earth’s magnetic poles flip-flop 3. Theory of Plate Tectonics - Movement is now explained by the theory of plate tectonics Earth’s outer shell is broken into rigid plates that move Plate boundaries are identified by earthquakes and volcanoes Plates interact along their boundaries
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