Cause of Plate Motions

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17.4

• Cause of Plate Motions

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Mantle

• Earths interior between the crust and the core
• Large-scale motion is believed to be the
  mechanism that drives the movement of tectonic
  plates

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Convection

• Transfer of thermal energy by the movement of
  heated material from one place to another
• Ex. Boiling water
• Heat comes from radioactivity within the mantle

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Convection Currents

• Cycle of warm water rising and cool water sinking
• The cooling of matter causes it to contract
  slightly and increase in density
• then it sinks due to gravity
• Warmed matter is then displaced and forced to rise

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Convection Currents

• Develop in the mantle
• Move the crust and outermost part of the mantle
• Transfer thermal energy from Earths interior to
  its exterior

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• Rising material spreads out, lifts and splits
  lithosphere at divergent boundaries
• Downward movement pulls convergent boundaries

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Ridge push

• Tectonic process associated with convection
  currents
• Occurs when the weight of an elevated ridge
  pushes an oceanic plate toward a subduction zone

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Slab pull

• Tectonic process associated with convection
  currents in Earths mantle
• Occurs as the weight of the subducting plate
  pulls the trailing lithosphere into a subduction
  zone.

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