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Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
Plate tectonics
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Plate tectonics

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  • 1. Plate Tectonics Continental Drift
  • 2. 4-1 Continental Drift – objectives…
    • Explain Wegener’s hypothesis of continental drift.
    • List evidence for Wegener’s hypothesis of continental drift.
    • Describe seafloor spreading.
  • 3. Continental Drift
    • Began with observations made over 400 years ago.
    • The first reliable maps were studied and it was noticed that the continents fit together like a puzzle.
  • 4. Hypothesis on Continental Drift.
    • The continents were once part of the same landmass – Pangea
    • Surrounding Pangea was a great ocean – Panthalassa
    • About 200 mya, Pangea began breaking apart.
    • This motion caused crumpling which led to today’s land features.
  • 5. Alfred Wegener
    • A german scientist.
    • Proposed his hypothesis on continental drift in 1912.
  • 6. Observations led to questions…
    • Were the continents once part of the same landmass?
    • If so, what caused this landmass to break apart?
    • What caused the continents to move to their present locations?
  • 7.  
  • 8.  
  • 9. Evidence
    • Coastline similarities
  • 10. Evidence
    • Fossils
      • Mesosaurus
      • Cynognatyhus
      • Lystrosaurus
      • Glossopteris
  • 11.  
  • 12. Geologic Evidence
    • Age and types of rocks
    • Mountains
      • Applachian mountains fit continuously with a band of mountains in Greenland.
  • 13. Climatic Evidence
    • Layers of glaciers in southern Africa and South America
    • Coal deposits in the Eastern US, Europe, and Sibera
    • These climatic similarities are easy to explain if the continents were once joined.
  • 14. Climatic Evidence - glaciation
    • Evidence of ancient glaciation indicated that parts of southern Africa, India, Australia, and South America were covered by a large ice sheet. Arrows indicate direction of ice movement.
  • 15. There was little support for Wegner’s hypothesis….until.two decades after his death…
  • 16. Seafloor Spreading
    • 1947, mapping the Mid-Atlantic Ridge
      • Discovered the ocean floor is much younger than continental rocks.
        • Oceanic rocks – 150 million years old
        • Continental rocks – 4 billion years old
    • Harry Hess suggested a hypothesis
      • Seafloor spreading
        • Rocks in/near the rift were younger as a result of the upwelling and solidification of magma.
  • 17. Seafloor Spreading
    • Seafloor spreading provided the support Wegner needed for a mechanism for continental drift.
    • Still no proof…
  • 18. Paleomagnetism
    • Magnetism resulting from the cooling of magma mirrors the existing magnetism of the earth.
    • Magnetic orientations were discovered that appeared normal then reversed…normal then reversed…
    • This supported seafloor spreading…and thus further anchored Wegner’s Hypothesis.
  • 19. Paleomagnetism
  • 20. Review of 4-1…
    • What observation first led to Wegner’s hypothesis of continental drift?
    • What types of evidence support Wegener’s hypothesis?
    • Describe the process of seafloor spreading.
    • Explain how scientists know that the earth’s magnetic poles have reversed themselves many times during earth’s history.
  • 21. 4-2 – Plate Tectonics - objectives
    • Summarize the theory of Plate Tectonics.
    • Compare the characteristic geologic activities that occur along the three types of plate boundaries.
    • Explain the possible role convection currents in plate movement.
    • Summarize the theory of suspect terranes.
  • 22. A theory emerges…
    • 1960’s…
    • A combination of continental drift and seafloor spreading…
    • Describes continental movement but also proposes a possible explanation of why and how continents move.
  • 23. The Earth’s Layers
    • Two types of crust:
      • Oceanic – ocean floor
      • Continental – dry land
    • Both types of crust plus the rigid upper mantle make up the Lithosphere.
    Himilayian Crust
  • 24. The Earth’s Layers
    • Lithosphere – the thin outer layer
      • Lithospheric plates
    • Asthenosphere – a layer of “plastic” rock
      • Denser than the lithosphere.
  • 25. Earth’s Layers
  • 26. Lithospheric Plate Boundaries
  • 27. Lithospheric Plate Boundaries
    • Continent margins don’t necessarily follow plate boundaries.
    • 30 plates have been identified at some speed of constant motion.
  • 28. Types of Plate Boundaries
  • 29. Divergent Boundaries
    • spreading centers where two lithospheric plates move away from each other
  • 30. Divergent Boundaries
  • 31. Convergent Boundaries
    • A converging boundary forms when two plates move toward each other
    • Two Types
      • Collision
      • Subduction
  • 32. Convergent Boundary - Collision
    • Oceanic crust – Oceanic crust
  • 33. Convergent Boundary - Collision
    • Oceanic crust – continental crust
  • 34. Convergent Boundaries
    • Continental crust – continental crust
  • 35.  
  • 36.  
  • 37. Transform Fault Boundaries
    • San Andreas fault, California
  • 38. Causes of Plate Motion
    • Many scientists think that the movement of the lithospheric plates is due to convection currents.
  • 39. Convection Currents

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