Plate Tectonics

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Chapter 8

• Plate Tectonics

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What is Plate Tectonics?

• Early Ideas
• Alfred Wegener
• Continental Drift
• Earths lithosphere moves over time - Pangaea
  (break up)
• Theory of Plate Tectonics

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Fossil Evidence
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Theory of Plate Tectonics

• The crust is divided into plates
• The plates move (a few cm/yr)
• Movement caused by mantle convection
• Different events occur at plate boundaries

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What is a Plate?

• Large slab of rock/Lithosphere
• Floats on crust (Asthenosphere)
• Oceanic is dense basalt
• Continental is lighter granite
• Size and thickness vary
• Oceanic is thin (15 KM)
• Continental is thick (200 KM)

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The Earths Plate Boundaries
Plate Movement
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Earthquakes and Volcanoes

• Ring of Fire
• Hot spots
• Formation of islands

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Ring of Fire
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Earthquakes
Volcanoes
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The Earths Plate Boundaries
Plate Movement
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Magnetism and the Ocean Floor

• Lava contains iron (magnetic)
• Mid-Ocean Ridge
• Earths North magnetic poleNorth Pole(normal
  polarity)
• Earths North magnetic poleSouth Pole (reverse
  polarity)
• Recorded in fossils and solidified igneous rock

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Types of Plate Boundaries

• Divergent Boundaries
• Convergent Boundaries
• Transform Boundaries

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Divergent Boundaries

• Plates move apart
• Ocean
• Sea floor spreading
• Land
• Rift Valleys
• Characteristic features
• Fracture zones
• Mid-ocean ridges/rift valleys
• Earthquakes and Volcanoes

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Divergent Plate Examples

• Mid-Atlantic Ridge
• East Pacific Rise
• East African Rift Zone

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Convergent Boundaries

• Plates move towards each other
• Subduction Boundary
• One plate moves underneath another
• Ocean/ocean - trenches form
• Ocean/Continent (subduction)
• Continent/Continent (Mountains)

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Convergent Examples
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Convergent ExampleVanuatu
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Transform Boundaries

• Plates slide past each other
• Earthquake activity
• Faults

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Transform Plate Movement
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San Andreas Fault
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2004 Asian Earthquake

• 9.0 magnitude
• Resulted in multiple tsunamis
• Up to 30 feet in height
• Traveling at speeds of 500 mph
• 700 miles of faultline slipped 50 feet vertically
• India plate pushed under the Burma plate (click
  to view map of plate movement)

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Eyewitness Video
Click to view video of tsunami as it strikes
Patong Beach, Thailand. This video takes a few
minutes to download 10MB (windows media player)
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Effects of 2004 Asian Earthquake

• Human loss
• Over 140,000 lost their lives
• Hundreds of thousands more were injured
• Millions were left homeless
• Threat of disease for survivors
• Destruction of property
• Click for video (realplayer)

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Arial of Tsunami Floodplain
Indonesian Coastline after 2004 tsunami
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Asian Tsunami 2004
Click on image for original movie
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Causes of Plate Movement

• Mantle Convection
• Ridge Push
• Slab pull

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Mantle Convection
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Ridge Push
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Slab Pull
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Push and Pull
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Plate Movement and Continental Growth

• Reconstructing the past
• Pangaea
• Craton
• Material sources of continental growth
• Igneous rocks
• River sediments
• Terrranes (crustal block or fragment)

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Learn More

• Try it for yourself
• Take an online quiz
• Labeling Quiz - Divergence
• Labeling Quiz - Convergence
• Flash cards
• Matching

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