Plate Boundaries

• The lithosphere is made from the crust and the uppermost part of the mantle

• The lithosphere is rigid, brittle rock

• These plates float on the asthenosphere

• Convection currents in the asthenosphere drive the movement of lithospheric plates

• Where two plates move away from each other. (divergent = divide)

  
  

• When oceanic plates diverge (sea-floor spreading), magma oozes out of the divergence, forming a mid-ocean ridge (underwater mountains)

  • Mid Atlantic Ridge

Oceanic-Oceanic

• When continental plates diverge, it forms a rift valley

  • East African Rift Valley

Continental-Continental

Oceanic-Oceanic

Continental-Continental

Two plates move toward each other. (convergent= collide)

Subduction: occurs when more dense tectonic plate slides under the less dense tectonic plate

• Oceanic Plate always subducts under continental plate

• forms volcanoes & trenches (can also have some earthquakes)

Oceanic-Continental

• Forms mountains

  • Himalayan Mountains

Continental-Continental

Oceanic-Continental

Continental-Continental

• Denser, older plate subducts

  • Forms deep sea trenches & Island Arc Volcanoes

    • Hawaiian Islands

Oceanic-Oceanic

• Two plates slide past each other

  • Causes Earthquakes

  • San Andreas Fault