Continental Drift and Plate Tectonics

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Continental Drift and Plate Tectonics
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Take-Away Points

• How we know plate tectonics happens
• Most earthquakes and volcanoes occur along plate
  boundaries
• New ocean crust is created along mid-ocean ridges
• Old ocean crust is recycled at subduction zones
• Subduction zones are where mountain-building
  (orogeny) occurs
• Small pieces of crust (terranes) are important in
  building up continents
• Hot spots are long lived stationary magma sources

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Global Problems in Geology

• Distribution of Continents
• Mid-ocean Ridges
• Trenches
• Orogenic Belts
• Deformation
• Metamorphism
• Volcanism
• Earthquakes

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Development of Continental Drift

• Lots of people had noticed that the coastlines of
  Africa and South America are similar
• Frank Taylor (1910)
• Alfred Wegener (1912) Die Entstehung Der
  Kontinente Und Ozeane

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The Permian Ice Age Problem
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Wegeners Theory
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Dating the Breakup
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Frank Taylor

• In some respects, Taylors ideas were more modern
  than Wegeners
• Taylor always thought Wegener had stolen credit
  from him

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Frank Taylor

• Recognized role of Mid-Atlantic Ridge
• Never reconstructed the continents like Wegener
  did

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Confirmation of Continental Drift

• World War II technology
• International Geophysical Year (IGY) 1957-58
• Worldwide Standardized Seismic Network 1963-

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The Geomagnetic Reversal Time Scale
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Discovery of Sea-Floor Spreading
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Sea-Floor Spreading
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Where Does Ocean Crust Go?

• Hugo Benioff, 1954

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Benioffs Interpretation
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Benioffs Interpretation Updated
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Worldwide Standardized Seismic Network
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The Plate Tectonics Model
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The Plate Tectonics Model
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The Earths Plates
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Global Plate Motions
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What Drives It Convection
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How Plates Move
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Reconstructing Plate Movements
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Fit of Continents Across the Atlantic
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Present Day Atlantic
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Atlantic 65 m.y. ago
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Geology of Plate Margins
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Ophiolites Oceanic Crust
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Anatomy of a Mid-Ocean Ridge
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FAMOUS Close-Up of the Mid-Atlantic Ridge
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Magnetic Stripes in the FAMOUS Area
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A Subduction Zone
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Why Mountains are High
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Where the Plates Meet
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Terrane Accretion
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Terranes in Western North America
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Plate Boundaries and Earthquakes
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Hot Spots
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Hot Spots Hawaii
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Pacific Hot Spot Tracks
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Take-Away Points Reviewed

1. How we know plate tectonics happens
2. Most earthquakes and volcanoes occur along plate
   boundaries
3. New ocean crust is created along mid-ocean ridges
4. Old ocean crust is recycled at subduction zones
5. Subduction zones are where mountain-building
   (orogeny) occurs
6. Small pieces of crust (terranes) are important in
   building up continents
7. Hot spots are long lived stationary magma sources