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Evidence of Crustal Motion • • • • Tilted sedimentary beds- (strata) Changes after an earthquake Changes in Bench Mark elevations Marine fossils high above the oceans (uplift- the rising of crust) • Shallow water fossils at great depth (subsidence- the sinking of crust) Sedimentary layers are deposited? Tilted Sedimentary Layers Show Changes after an earthquake. Changes in Benchmark Elevations What is the temperature in the earth’s core? What is the pressure at the outer core inner mantle interface(boundary)? What is the pressure at the asthenosphere? Scientists once believed that continents fit into the crust and drifted from place to place. German Scientist Alfred Wegener proposed in 1912 that all of the continents were together at one time. If you put the continents together they fit like a jigsaw puzzle. He called this_________________. Scientists disagreed with the theory that the continents plowed through the crust. Common sense would prove that the continents would have to be part of the crust. Evidence from the ocean floors led to the modern theory of….. The Earth is composed of about a dozen rigid plates that are moving with several smaller plates. The plates contain areas of light continental rock (felsic) as well as dense oceanic bottoms(mafic) The Earth’s outer layer is called the lithosphere. It is made of the rigid upper mantle and the crust. The lithosphere moves on the asthenosphere, part of the mantle that flows. Convection occurs due to density differences. Hot liquid is less dense and rises when more dense liquid is pulled down by gravity. Forces in the Earth come from the heat being released from deep inside. •The heat is left over from the formation of the earth and the radioactive elements in the earth. •The heat is passed by conduction in solids and convection in liquids. Convection in the Earth Evidence of Plate Tectonics 1. Newer Crust at Mid Oceanic Ridges 2. Warmer Crust at MOR 3. Earthquakes and Volcanos found in belts around the world. 4. Earthquakes are deeper as you move inland at a subduction zone. 5. Magnetic Sea Floor Banding Seafloor Spreading Video http://www.youtube.com/watch?v=6CsTTmvX6mc&safe=active Convection in the Earth Magnetic Seafloor Banding: Iron bearing minerals in molten material will orient in a north south direction. Paleomagnetism