DYNAMIC EARTH Chapter 8: Plate Tectonics

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DYNAMIC EARTHChapter 8 Plate Tectonics

• 8.1 What is Plate Tectonics
• 8.2 Types of Plate Boundaries
• 8.3 Causes of Plate Movement
• 8.4 Plate Movements and Continental
  Growth

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8.1 What is Plate Tectonics

• Plate Tectonics-The Theory that describes the
  formation, movements, and interactions of
  lithospheric plates.
• Early Ideas about Plate Movements
• 1400s-explorers using maps noted the remarkable
  fit of Africa with S. America
• 1912-Alfred Wegner proposed the hypothesis of
  Continental Drift. It said that continents have
  moved or drifted over time. However, it didn't
  say how.

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8.1 What is Plate Tectonics

• The Theory of Plate Tectonics
• Says that the continents are embedded on
  lithospheric plates that move. Movement Video
• Based on a wealth of evidence.
• Explains why earthquakes and volcanoes are found
  in clusters. See page 173.
• Magnetism helps to support the idea of sea floor
  spreading. See page 174.
• Mid-Ocean Ridge- A long chain of volcanic
  mountains on the ocean floor with a deep central
  valley. Younger rocks are found a both sides of
  the ridge.

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8.2 Types of Plate Boundaries

• Divergent Boundaries
• A boundary between two lithospheric plates that
  are moving apart.
• Create rift valleys-deep valleys at the center of
  a mid-ocean ridge.
• Mid-Atlantic Ridge and East Pacific Rise

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8.2 Types of Plate Boundaries

• Convergent Boundaries
• A boundary between two plates that are moving
  toward each other, or converging.
• The boundary is called a Subduction boundary and
  creates a deep-sea trench. See page 177.
• Creates Volcanoes. Draw picture from page 177.
• Collision boundaries are created when two
  continents collide. The Himalayas are a good
  example.

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8.2 Types of Plate Boundaries

• Transform Boundaries
• Boundary between two plates that are sliding past
  each other.
• San Andreas Fault is the best example. See page
  178.
• study chart on page 179.

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Boundaries
Boundaries in Action Continental Growth
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8.3 Causes of Plate Movement

• The ocean boils under our surfboards!
• Mantle Convection
• Heat from Earth's inner and outer core is
  transferred through the mantle by this process.
  See page 180.
• Remember heat rises!
• (Draw picture below)

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8.3 Causes of Plate Movement

• Ridge Push Slab Pull
• Cooling, subsiding rock exerts a force on
  spreading lithospheric plates that could help
  drive their movements.
• The heavier plate sinks and then pulls the rest
  of his body with him. (I'm Melting)

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8.4 Plate Movements Continental Growth

• Reconstructing the Past
• Based on lots of evidence fossils, mountain
  belts, magnetic records and rock outcrops.
• Plate Tectonics and Pangaea
• Pangaea-Evidence indicates that around 250 mya,
  all of the continents were welded into one
  landmass.
• Gondwana-Group of smaller landmasses that
  converged together to create Pangaea. See page
  182.

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8.4 Plate Movements Continental Growth

• Pangaea then broke up into smaller continents and
  eventually arrived at our current locations.
  These continents are still on the move. See page
  182 again.
• Plate Tectonics and Continental Growth
• Craton-An expanse of ancient rock at the core of
  a continent.
• Continents have grown and changed shape over
  time.

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8.4 Plate Movements Continental Growth

• Sources of Growth Material
• Added material comes from deep-sea sediments,
  igneous rock, and river sediments.
• Deep-sea sediments are added when an oceanic
  plate plunges beneath a continental plate at a
  Subduction boundary. Some of the ocean floor
  sediment is scarped off the plate and left on the
  edge.

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8.4 Plate Movements Continental Growth

• 3. Igneous rock- Comes from rising magma,
  which creates volcanoes along plate boundaries.
• 4. River Sediments- Erosion and weathering of
  earth material creates new sediments, which build
  up on the edge of continents.
• Pangea
• Future Plate Movement