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Transcript
Theory of Plate Tectonics Review of Earth’s Layers Review of Earth’s Layers • Crust – thinnest, outermost layer of Earth • Lithosphere – rigid layer consisting of the crust and uppermost part of the mantle • Asthenosphere – soft layer of the mantle on which pieces of the lithosphere float • Mantle – layer of hot, mostly solid material between the crust and core • Outer Core – layer of molten iron and nickel that surrounds the inner core • Inner Core – dense sphere of solid iron and nickel at the center of the Earth Alfred Wegner • (1910s) German scientist who believed all continents were once joined together in one giant landmass called... ▫ PANGAEA • This was the basis for the theory of.... ▫ CONTINENTAL DRIFT Continental Drift • Wegner’s EVIDENCE... 1. Puzzle-Like Fit of Continents 2. Matching Fossils (animals and plants) 3. Matching Mountain Ranges (Sedimentary Rock Layers) 4. Glacial Remains in Tropical Areas 5. Tropical Plant Fossils Found in Arctic Areas 6. Longitudinal data of Greenland did not match earlier explorer’s data Continental Drift Continental Drift • Wegner could NOT prove how the continents moved, thus scientists did NOT accept the Continental Drift theory. New Theory forms... • Continents don’t move... • Earth’s PLATES move • This theory is called... ▫ PLATE TECTONICS Plate Tectonics • Evidence... ▫ SEAFLOOR SPREADING – the seafloor moves apart and magma rises up to fill in the space creating new crust ▫ Magnetic patterns and the Mid-Atlantic Ridge were discovered on the ocean floor using large-scale sonar Plate Tectonics • According to the Theory of Plate Tectonics... ▫ The lithosphere is broken up into 9 major and many smaller plates. ▫ They float on top of the semi-liquid asthenosphere ▫ CONVECTION CURRENTS in the asthenosphere slowly MOVE the plates Plate Tectonics • Lithosphere ▫ Top layer of the Earth which contains the “plates” • Asthenosphere ▫ Partially molten layer of Earth right below the Lithosphere. ▫ There are CONVECTION CURRENTS in the Asthenosphere that slowly MOVE Earth’s plates (the Lithosphere) Lithosphere and Asthenosphere Convection Currents in the asthenosphere Convection Currents in the asthenosphere Earth’s Plates – Boundary Map 3 Types of Boundaries 1.Divergent 2.Convergent 3.Transform Divergent Boundaries • Movement: 2 plates SLIDE APART or diverge • Forms: RIFT VALLEYS and MID–OCEAN RIDGE • Sea-floor spreading occurs here Divergent Boundaries Sea-Floor Spreading Rift valley Divergent Boundaries Convergent Boundaries • Movement: 2 plates SLIDE TOGETHER or converge • Forms: MOUNTAINS, VOLCANOES, TRENCHES, and ISLAND ARCS Convergent Boundaries Convergent Boundaries Convergent Boundaries Subduction Zone The denser plate (oceanic) will be recycled into the mantle Volcano Trench Convergent Boundaries Transform Boundaries • Movement: 2 plates SLIDE PAST each other, moving IN OPPOSITE DIRECTIONS • Forms: FAULTS are created Transform Boundaries 1. Which boundary is this? 2. Which boundary is this? 3. Which boundary is this? 4. Which boundary is this? 5. Which boundary is this? 6. Which boundary is this? 7. Which boundary is this? 8. Which boundary is this? 9. Which boundary is this?
