Sea Floor Spreading and Plate Tectonics

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Sea Floor Spreading and Plate Tectonics
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Hess Sea Floor Spreading
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Spreading can explain previous observations
Magnetic anomalies
Age of oceanic crust
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Plate Tectonic Theory (PTT)

• Earths crust and rigid upper mantle are broken
  into enormous slabs called plates
• Solid plates sit and ride on molten asthenosphere
  (also part of mantle)
• Plates move in different directions and at
  different rates
• Sea floor spreading gives a mechanism (ie the
  HOW)

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Inside the Earth
Solid plates ride on molten asthenosphere
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7 Major Plates

• North America
• South America
• Pacific
• African
• Eurasian
• Australian-Indian
• Antarctic

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Boundary Types(Divergent, Convergent, and
Transform)
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Transform Boundary
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Transform Boundary, contd
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Some other vocabulary

• Rift
• Ridge
• Trench
• Subduction Zone
• Continental crust is less dense than oceanic
  crust
• Lithosphere/Asthenosphere
• Volcanic arc/island arc