Sea Floor Spreading Expanding Earth or Plate Tectonics Mr. Clement Cheng

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Sea Floor SpreadingExpanding Earth or Plate
TectonicsMr. Clement Cheng
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Continental Drift Theory

• Objection 1
• No one could explain how continents could be
  moved
• Objection 2
• Wegener was not a physical geologists but a
  climatologist.

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Sea Floor Spreading

• Proposed by Hess in 1960
• New discoveries about the deep ocean floor
  formulated

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Evidence 1 The Mid-oceanic Ridge
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Evidence 2 Magnetic Anomaly
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How are magnetic anomalies generated?
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Evidence 3 Young Ocean Floor(JODIES)
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Evidence 4 Heat Flow
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Important Point to Note Sea-floor spreading
is the mechanism that generates divergent plate
boundaries creates oceanic crust and separates
continents.
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1. Divergent Plate Boundaries
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2. Generating Oceanic Crust
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3. Leading to Continental Drift
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Actual Examples
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So?????

• Expanding earth
• OR
• Another mechanism for subduction zone in order to
  maintain steady-state equilibrium