Plate Boundaries

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  • Created by: Jelena
  • Created on: 14-05-13 23:10

Divergent Boundaries

Plates move apart and new lithosphere is created.

A. Oceanic Plate Separation

  • On the ocean floor, the boundary between separating plates is marked by a mid-ocean ridge (ex. Mid-Atlantic Ridge)

B. Continental Plate Separation

  • When continental crust begins to separate, the stretched crust forms a long, narrow depression called a rift valley (ex. Great Rift Valley, Africa)
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Convergent Boundaries

Plates come together and one is recycled back into the mantle.

A. Ocean - Ocean Convergence

  • Two plates are oceanic --> one descends beneath the other in a process called subduction
  • The oceanic lithosphere of subducting plate sinks into asthenosphere and, replaced by mantle convection system
  • This downward buckling produces a long, narrow deep-sea trench (ex. Marianas Trench of the western Pacific)

B. Ocean - Continent Convergence

  • If one plate has a continental edge, it overrides the oceanic plate b/c the continental crust is lighter and less easily subducted than oceanic crust
  • The continental ledge crumples and is uplifted into a mountain chain (ex. the Andes)
  • The enormous forces of collision and subducton produces great earthquakes

C. Continent - Continent Convergence

  • Two continental plates collide --> crust crumples and thickens, creating high mountains and a wide plateau (ex. Himalaya and Tibetan Plateau)
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Transform-Fault Boundaries

  • Boundaries where the plates slide past each other, lithosphre is not created or destroyed
  • As plates slide past one another, fractures are created
  • Large earthquakes can occur on transform-fault boundaries
  • Ex. San Andreas fault in California
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