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Earth Science

Earth Science. Structure of the earth. Tectonics. Continental Drift . Wegener’s Continental Drift Hypothesis (1912) stated that the continents had once been joined to form a single supercontinent (Pangaea) .

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Earth Science

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  1. Earth Science

  2. Structure of the earth

  3. Tectonics

  4. Continental Drift Wegener’s Continental Drift Hypothesis (1912) stated that the continents had once been joined to form a single supercontinent (Pangaea). Wegener proposed that Pangaeabegan to break apart 200 million years ago and formed the present landmasses.

  5. Continental Drift

  6. Continental Drift Evidence • The Continental “Puzzle” • Matching Fossils • Rock Types and Structures • Ancient Climates

  7. Matching Mountain Ranges

  8. Glacier Evidence

  9. Continental Drift Wegener could not provide an explanation of what made the continents move. New technology led to findings which then led to a new theory called plate tectonics

  10. Plate Tectonics • According to the plate tectonics theory, the uppermost mantle, along with the crust, behaves as a strong, rigid layer (lithosphere) • A plateis one of numerous rigid sections of the lithosphere that move as a unit over the “softer” asthenosphere

  11. Plate Boundaries • Divergent boundaries (spreading centers) are the place where two plates move apart • Convergent boundaries form where two plates move together • Transform fault boundaries are margins where two plates grind past each other without the production or destruction of the lithosphere

  12. Plate Boundaries

  13. Divergent Boundaries • Oceanic ridges are continuous elevated zones on the floor of all major ocean basins. • Rift valleys are deep faulted structures found along the axes of divergent plate boundaries. They can develop on the seafloor or on land • Seafloor spreading produces new oceanic lithosphere

  14. Divergent Boundaries

  15. Continental Rifts

  16. Convergent Boundaries A subduction zone occurs when one oceanic plate is forced down into the mantle beneath a second plate Oceanic-Continental: • Denser oceanic slab sinks into the asthenosphere; Pockets of magma develop and rise • Continental volcanic arcs form; Andes, Cascades

  17. Convergent Boundaries

  18. Convergent Boundaries Oceanic-Oceanic • Two oceanic slabs converge and one descends beneath the other • Volcanic island arcs form as volcanoes emerge from the sea • Examples include the Aleutian, Mariana, and Tonga islands

  19. Convergent Boundaries

  20. Convergent Boundaries Continental-Continental • When both subducting plates contain continental material • This kind of boundary can produce new mountain ranges, such as the Himalayas

  21. Convergent Boundaries

  22. Transform Fault Boundaries • Plates grind past each other without destroying the lithosphere • Most join two segments of a mid-ocean ridge • At the time of formation, they roughly parallel the direction of plate movement • They aid the movement of oceanic crustal material

  23. Transform Fault Boundaries

  24. Summary of Plate Boundaries

  25. Evidence for Plate Tectonics Paleomagnetism is the natural remnant magnetism in rock bodies; is permanent • This can be used to determine the location of the magnetic poles at the time the rock became magnetized Normal polarity— rocks show the same magnetism as the present magnetic field

  26. Evidence for Plate Tectonics Reverse polarity— rocks show the opposite magnetism as the present magnetic field • The discovery of strips of alternating polarity across the ocean ridges, is among the strongest evidence of seafloor spreading

  27. Evidence for Plate Tectonics

  28. Evidence for Plate Tectonics Hot Spots • A hot spot is a concentration of heat in the mantle capable of producing magma, which rises to Earth’s surface; • Hot spots occur in the middle of a plate • The Pacific plate moves over a hot spot, producing the Hawaiian Islands • Hot spot evidence supports that the plates move

  29. Evidence for Plate Tectonics

  30. Convection: The Force Behind Tectonics

  31. Earth's Tectonic Future

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