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  • 1. Plate Tectonics Chapter 17 Great Idea: The entire earth is still changing, due to the slow convection of soft, hot rocks deep within the planet.
  • 2. Chapter Outline
    • The Dynamic Earth
    • Plate Tectonics: A Unifying View of Earth
    • Another Look at Volcanoes and Earthquakes
  • 3. Science by the Numbers
    • How long could a mountain last?
    • The case of the disappearing mountains
  • 4. The Case of the Disappearing Mountains
    • Erosion
      • Few hundred million years
      • Mountains continually forming
    • Earth’s surface is not static
  • 5. Pike’s Peak in Colorado, US
  • 6. Slopes and Peaks in Young and Older Mountains
  • 7. The Dynamic Earth
  • 8. The Dynamic Earth
    • Small-scale changes
      • Construction site
        • Erosion by rain
    • Large-scale changes
      • Volcanoes
      • Earthquakes
      • Erosion
  • 9. Volcanoes and Earthquakes- Evidence of Earth’s Inner Forces
    • Volcano
      • Magma breaks through surface
    • Earthquake
      • Rocks breaks along fault
      • Energy transmitted as wave
      • Richter scale
  • 10. Mount St. Helens – Active Volcano
  • 11. Cross Section of a Volcano
  • 12. Earthquake Scarp
  • 13. Tsunami
  • 14. The Movement of the Continents
    • Francis Bacon
      • Continents like a puzzle
    • Alfred Wegener
      • Continental Drift
        • Continents in motion
  • 15. Continental Atlantic Coastlines
  • 16. The Movement of the Continents – cont.
    • Current Evidence
      • Ocean floors
      • Magnetic reversals
      • Rock ages
  • 17. Ocean Floors
    • Mapping
      • Ocean floor dynamic
        • Canyons, mountains
        • Mid-Atlantic Ridge
          • Earthquakes, volcanoes, lava flows
  • 18. Topographic Map of the Ocean Floor
  • 19. Magnetic Reversals
    • Earth’s magnetic field
      • Changes periodically
    • Magnetite
      • Crystals in lava align to magnetic field
    • Paleomagnetism
    • Seafloor spreading
      • New rock comes to surface
  • 20. Parallel Magnetic Strips
  • 21. Magnetic Strips that Parallel Ocean Ridges
  • 22. Rock Ages
    • Radioactive isotopes
      • Rocks near Mid-Atlantic Ridge younger
      • Rocks farther away older
  • 23. New Support for the Theory
    • Measuring motion of continents
    • Radio astronomy
      • Measured arrival of radio waves
      • Repeated over several years
    • North America and Europe
      • Separating at 5 cm per year
  • 24. Science by the Numbers
    • The age of the Atlantic Ocean
    • Pangaea
  • 25. Plate Tectonics: A Unifying View of Earth
  • 26. Plate Tectonics
    • Plate tectonics
      • Large-scale surface features
      • Related phenomena
  • 27. Plate Tectonics – cont.
    • Tectonic plates
      • Rigid, moving sheet of rock
      • Crust and upper mantle
      • Continental
        • 100 km thick
        • Lower density (granite)
      • Oceanic
        • 8-10 km thick
        • Dense rock (basalt)
  • 28. Plate Tectonics – cont.
    • Earth’s surface
      • ¼ continent, ¾ water
  • 29. Earth’s Major Plates and Direction of Motion
  • 30. The Convecting Mantle
    • Mantle convection
      • Motion driven by Earth’s interior heat energy
    • Sources of energy
      • Gravitational potential energy
      • Decay of radioactive elements
  • 31. The Convecting Mantle – cont.
    • Movement
      • Heat moves to cooler regions
      • Convection cells in mantle
      • Very slow
        • 200 million years for one cycle
  • 32. Mantle Convection
  • 33. Science in the Making
    • Reactions in plate tectonics
    • Pioneer expedition
  • 34. Plate Boundaries
    • Three main boundary types
      • Divergent
      • Convergent
      • Transform
  • 35. Divergent Boundaries
    • Characteristics
      • Volcanoes
        • Chain of mountains
      • Earthquakes
  • 36. Divergent Plate Boundary
  • 37. Divergent Boundaries – cont.
    • Seafloor spreading
      • Plates pushed apart
      • Old spreading centers
        • Located in middle of ocean
      • New spreading centers
        • May begin anywhere
  • 38. Africa’s Great Rift Valley
  • 39. Convergent Plate Boundaries
    • Types
      • Oceanic-oceanic
        • Subduction zone
          • Deep oceanic trench
          • Island arc
  • 40. Ocean-Ocean Plate
  • 41. Convergent Plate Boundaries- cont.
      • Continental-continental
        • High, jagged mountain chain
  • 42. Continental-Continental Plate
  • 43. Convergent Plate Boundaries- cont.
      • Continental-oceanic
        • Subduction zone
          • Deep oceanic trench
          • Coastal mountain range
  • 44. Ocean-Continental Plate
  • 45. Transform Plate Boundary
    • Two plates move past each other
      • NOT smooth
      • Earthquakes as a result of movement
  • 46. Transform Plate Boundary
  • 47. The Science of Life
    • Upright posture
    • Contributions by Richard Leakey
  • 48. The Geological History of North America
    • Northeastern Canada and Greenland
      • Several billion years old
    • Western US
      • Terranes
        • Added to continent over time
    • Appalachian Mountains
      • Formed 450-300 million years ago
      • Continental-continental convergence zone
  • 49. The Geological History of North America – cont.
    • Rocky Mountains
      • 60 million years ago
      • Warping, folding and fracturing of continent
    • The Colorado Plateau
      • Gentle uplift
    • The Sierra Nevada
      • Molten rock pushed up sediments
  • 50. US Mountains
  • 51. Another Look at Volcanoes and Earthquakes
    • Plates and volcanism
      • Divergent plate boundaries
      • Convergent plate boundaries
        • Subduction zones
      • Hotspots
        • Source stationary, plates move
        • Chain of volcanoes
    • Earthquakes
      • At plate boundaries or elsewhere
  • 52. Volcanoes Form Above a Subduction Zone
  • 53. The Hawaiian Islands
  • 54. Seismology: Exploring Earth’s Interior with Earthquakes
    • Seismology
      • Study of sound vibrations within earth
      • Used to determine earth’s inner structure
    • Seismic waves
      • Compressional or longitudinal
      • Transverse or shear waves
    • Earthquake predictions
  • 55. Seismic Waves Passing through Earth
  • 56. The Ongoing Process of Science
    • Seismic tomography
  • 57. Technology
    • The design of earthquake-resistant buildings