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Earth Science Physical Geology

Earth Science Physical Geology

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Earth Science Physical Geology

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  1. Earth SciencePhysical Geology Plate Tectonics Chapter 4 Notes 1

  2. Continental Drift • Alfred Wegener (1912) • German scientist • All continents were once in one super continent called Pangaea • During the Mesozoic Era, began to break up • Wegener died before he found the reason for continental drift

  3. Evidence of Continental Drift • Similarities in coastlines • Fossils of the same plants and animals are found on different continents • Geological evidence begins on one continent and ends on another • Climate patterns • Coal deposits found in cold regions • Evidence of glaciers can be found in tropical areas

  4. Final Evidence • Seafloor Spreading • In 1947, scientist mapped the Mid-Atlantic Ridge • Found rocks closest to the ridge were younger than the rocks closer to the continents

  5. Paleomagnetism • Evidence for Seafloor Spreading • Found there are bands of rocks on the ocean floor that have alternating polarities • Normal = minerals pointing north • Reverse = minerals pointing south • Earth’s magnetic field has reversed itself many times in earth’s history

  6. Paleomagnetism

  7. Theory of Plate Tectonics • Earth’s Crust: • Oceanic • Continental • Together with the rigid upper mantle make the lithosphere • broken into plates that are carried like blocks of wood on water • Float on top of the asthenosphere (like putty)

  8. Lithospheric Plate Boundaries • Divergent Boundaries • Two plates moving away from each other • Molten rock fills in the crack that is formed • Most are found on oceanic boundaries • Ex: Mid-Atlantic Ridge • Convergent Boundaries • Two plates moving toward each other

  9. Convergent Boundaries • Oceanic and continental crust • Oceanic crust is denser and subducted (forced under the other) • Creates a subduction zone, where the oceanic crust is pushed under the continental crust • Also creates a deep ocean trench • Water seeps into the mantle and melts the mantle; creates magma and volcanic eruptions

  10. Convergent Boundaries • Continental and continental crust • Both are pushed upward • Produces large mountains like the Himalayas • Oceanic and oceanic crust • One plate is subducted, creates a deep ocean trench • Magma is made and a volcanic island is created • Called an island arc

  11. Transform Boundary • Two plates grind past one another horizontally • Sudden spurts of movement • Ex: San Andreas Fault in California

  12. Causes of Plate Motion • Convection: transfer of heat through movement of heated material • Hot material rises; Cold material sinks • Creates a convection current • Believe there are convection currents in the asthenosphere • As the plates move apart, upwellings from deep in the mantle replace the hard lithosphere • As the lithosphere becomes older, colder and denser, it begins to sink back into the mantle

  13. Homework Study for Quiz on Ch. 4 Do Key Terms