Plate Tectonics

Earth's Continental Plates

  • Distinct boundaries of the Earth's crust
  • Explains how slow motions within Earth's mantle move large segments of the crust
  • Results in a gradual drifting of the continents
  • Forms mountains and other large-scale geological features
  • Cooling system for the planet
    • Heat from inside --> outside
  • There are ~12 tectonic plates on Earth
  • Plates are moved by convection of the mantle
  • Four basic interactions between plates at their boundaries
    • Pull apart (rift zone)
    • One plate burrows under another (subduction zone)
    • Slide alongside each other (fault zone)
    • Jam together
  • Constantly renews Earth's crust and erases cratering events

Rift and Subduction Zones

  • Rift zones
    • Plates pull apart from each other
    • Most found in the oceans
  • Subduction zones
    • Two plates come together, one is forced beneath another
    • Thinner oceanic plates can be readily thrust down into upper mantle
    • Often marked by ocean trenches

Fault Zones

  • Crustal plates sliding parallel to each other
  • Marked by cracks or faults
  • Motion builds up stresses in the crust and released in sudden, violent slippages
    • This generates earthquakes
    • The longer the interval between earthquakes, the greater the stress and more energy released when the surface finally moves

Geology Earth