Theory of Plate Tectonics

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Theory of Plate Tectonics
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Continental Drift

• The geological theory by Alfred Wegner that
  states that Earths continents were once ONE
  large landmass Pangea and over time the
  continents slowly moved apart.
• Evidence...
• Shape of the Earths continents
• They look like they fit together like pieces of a
  puzzle

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Continental Drift

• This theory was NOT CORRECT!!

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Plate Tectonics

• The geological theory by Tuzo Wilson that states
  that pieces of Earths lithosphere are in
  constant slow motion.
• Evidence
• The SAME FOSSILS on different continents
• Magnetic patterns found on the ocean floor at
  along a mid-ocean ridge.

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Plate Tectonics Lithosphere

• Lithosphere
• Top layer of the Earth which contains the
  plates
• Asthenosphere
• Partially molten layer of Earth right below the
  Lithosphere.
• There are convection currents in the
  Asthenosphere that slowly move Earths plates
  (the Lithosphere)

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Lithosphere and Asthenosphere
Convection Currents in the asthenosphere
Convection Currents in the asthenosphere
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Earths Plates Boundary Map
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3 Types of Boundaries

• Transform
• Divergent
• Convergent

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Transform Boundaries

• 2 plates slide past each other, moving in
  opposite directions
• Along these boundaries, crust is neither created
  or destroyed
• Earthquakes occur here
• Faults are created

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Divergent Boundaries

• 2 plates slide apart or diverge
• Forms rift valleys and mid-ocean ridge
• Sea-floor spreading occurs here

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Divergent Boundaries

• Sea-Floor Spreading

Rift valley
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Convergent Boundaries

• 2 plates slide together or converge
• Results in a collision
• Denser crust will be on the bottom (oceanic
  crust)
• Usually forms mountains, volcanoes, trenches, and
  a subduction zone

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Convergent Boundaries

• Subduction Zone
• The denser plate (oceanic) will go into the Earth

Volcano
Trench
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1. Which boundary is this?
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2. Which boundary is this?
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3. Which boundary is this?
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4. Which boundary is this?
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5. Which boundary is this?
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6. Which boundary is this?
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7. Which boundary is this?
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8. Which boundary is this?
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9. Which boundary is this?
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Plate Tectonics vs. Continental Drift
Plate Tectonics
Continental Drift
Plates are moving.
Continents are moving.
Move
Theory by Alfred Wegner
Theory by Tuzo Wilson