C:\Users\Lisa Knight\Desktop\A Scientific Revolution Begins
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C:\Users\Lisa Knight\Desktop\A Scientific Revolution Begins C:\Users\Lisa Knight\Desktop\A Scientific Revolution Begins Presentation Transcript

  • Plate Tectonics A scientific revolution begins
  • Continental drift and paleomagnetism
    • Renewed interest in continental drift initially came from rock magnetism
    • Magnetized minerals in rocks
        • Show the direction to Earth’s magnetic poles
        • Provide a means of determining their latitude of origin
  • Continental drift and paleomagnetism
    • Polar wandering
        • The apparent movement of the magnetic poles illustrated in magnetized rocks indicates that the continents have moved
        • Indicates Europe was much closer to the equator when coal-producing swamps existed
  • Continental drift and paleomagnetism
    • Polar wandering
        • Curves for North America and Europe have similar paths but are separated by about 24  of longitude
          • Differences between the paths can be reconciled if the continents are placed next to one another
  • Polar-wandering paths for Eurasia and North America Figure 2.11
  • A scientific revolution begins
    • During the 1950s and 1960s technological strides permitted extensive mapping of the ocean floor
    • Seafloor spreading hypothesis was proposed by Harry Hess in the early 1960s
  • Seafloor spreading occurs along the oceanic ridges
  • A scientific revolution begins
    • Geomagnetic reversals
        • Geomagnetic reversals are recorded in the ocean crust
        • In 1963 Vine and Matthews tied the discovery of magnetic stripes in the ocean crust near ridges to Hess’s concept of seafloor spreading
  • Paleomagnetic reversals recorded in oceanic crust Figure 2.16
  • A scientific revolution begins
    • Geomagnetic reversal
        • Paleomagnetism was the most convincing evidence set forth to support the concepts of continental drift and seafloor spreading
  • Plate tectonics: The new paradigm
    • Earth’s major plates
        • Associated with Earth's strong, rigid outer layer
          • Known as the lithosphere
          • Consists of uppermost mantle and overlying crust
          • Overlies a weaker region in the mantle called the asthenosphere
  • Plate tectonics: The new paradigm
    • Earth’s major plates
        • Seven major lithospheric plates
        • Plates are in motion and continually changing in shape and size
        • Largest plate is the Pacific plate
        • Several plates include an entire continent plus a large area of seafloor
  • Earth’s plates Figure 2.19 (left side)
  • Earth’s plates Figure 2.19 (right side)
  • Plate tectonics: The new paradigm
    • Earth’s major plates
        • Plates move relative to each other at a very slow but continuous rate
          • About 5 centimeters (2 inches) per year
          • Cooler , denser slabs of oceanic lithosphere descend into the mantle