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Transcript
Crustal Movement Layers of The Earth • Core – Center of the earth – Contains Iron and Nickel – Two Levels • Inner Core – Solid – Yes there is tremendous heat but it is out weighed by the enormous pressure which pushes the particles of Iron and Nickel so close together that they remain solid. • Outer Core – Liquid – Here heat out weighs the pressure and the Iron and Nickel are molten Mantle • Middle layer of the Earth • Comprised mostly of silicon, oxygen, iron, and magnesium. Crust • Solid and rocky outer layer of the earth – Think of the crust like an apple peel – very thin outer layer. – Types • Oceanic – Crust beneath the ocean – Comprised of silicon, oxygen, iron, and magnesium • Continental – Crust beneath the continents – Comprised mostly of silicon, oxygen, aluminum, calcium, sodium, and potassium. Crust • Levels –Lithosphere • Solid topmost part of the Earth –Asthenosphere • Often considered to be the upper edge of the mantle –Made of molten material –Property of Plasticity »Able to flow or move easily Activity • Draw your own version of the Earth’s Layers Plate Tectonics • Continental Drift Theory –Alfred Wegener –1912 Plate Tectonics • Continental Drift –The Theory • All of the continents were once joined in one large land mass, Pangaea, that began breaking up and drifting apart millions of years ago • Wegener’s theory was very unpopular and rejected by most of the world’s scientists. Plate Tectonics • Continental Drift – The Evidence • Identical types of fossils were found in Africa and South America • Many of the Earth’s rock formations line-up with formations on other continents. – Mountain ranges in African line up with matching ones in South America. – Coal fields with distinct layers in Brazil match up with identical fields in Africa Plate Tectonics • Continental Drift –The Evidence • Glacial Deposits (Sediments and Rocks left behind by glaciers) have been found in South America, Africa, India, and Australia. • The Continental coast lines fit together like the pieces of a puzzle. Plate Tectonics • Sea-Floor Spreading –Harry Hess –1960 Plate Tectonics • Sea-Floor Spreading –Discovered a large system of underwater mountains. • Contain a deep crack –Lava erupts through these cracks pushing the ocean floor on either side away. –The lava hardens and forms new ocean floor. Plate Tectonics • Sea-Floor Spreading – The evidence • Samples have shown that the further away from a ridge you get the older the rock. • Magnetic memory of rock material in the ocean – As magma hardens at ridges half of the rock moves in one direction and half moves in the other. » On each side the magnetic strips match the earth’s magnetic pull. Plate Tectonics • Plate Tectonics –J. Tuzo Wilson - 1965 Plate Tectonics • Plate Tectonics –Plate • The moving, irregularly shaped slabs that fit together like paving stones to form the surface layer of the earth –Tectonics • The branch of geology that deals with the movements that shape the earth’s crust Plate Tectonics • Plate Tectonics – The Theory • The earth’s plates are in constant, slow motion, driven by convection currents in the mantle. – Do you know what convection is? • Seven Major Plates – Named for the area its surface features. » For example – The Pacific Plate • Can move up to several centimeters per year. Plate Tectonics • Plate Tectonics –Convection • Hot material rises from the core and cool material sinks towards the core. • The cool material then heats and the rises this circular cycle causes movement. Activity • Draw your own model of convection currents. Plate Tectonics • Plate Tectonics –Plate Boundaries • The points where plates meet. –3 Types »Divergent »Convergent »Transform or Strike-Slip Plate Tectonics • Plate Tectonics – Divergent • Move apart at mid-ocean ridges. Plate Tectonics • Plate Tectonics – Boundaries • Convergent – Plates come together at trenches – One plate moving over top of the other. Plate Tectonics • Plate Tectonics – Boundaries • Strike-Slip – Two plates grind together and slip past each other horizontally. No new material is created and none is destroyed. Geological History • Fossils –Preserved remains or traces of living things –Can be used to determine age. Geological Time Scale • Fossils –Law of Superposition • In horizontal sedimentary rock layers, the oldest rock is on the bottom Geological History • Fossils –How do you think Paleontologist determine the age of fossils? • Radioactive (Carbon) Dating –Determines the absolute age of rocks and fossils. –The rate at which a radioactive element decays is a constant. »Half Life Geological History • Fossils –Index Fossils • The remains of plants and animals that existed for a relatively short period of time in a wide area. • Tell the relative age of rocks Geological History • Geological Time Scale – Eras – Plaeozoic, Mesozoic, Cenozoic – Periods – Eras are divided into periods. – Epochs – Only in the Cenozoic period because the information we have for this era is so much more complete.