Crust

• The dynamic earth


  7 major and 8 minor plates on the earths surface

  The major plates have continents on them
• Continental crust


  -less dense

  -average thickness 35-40km

  -felsic (acidic) composition

  -common element, silica

  -common rock type, granite
• Oceanic Crust


  -more dense

  -average thickness 10km

  -mafic, rich in iron

  -common rock type, basalt
• Alfred Wenger


  scientist who came up with the continental drift theory- the continents were once all together

  Using evidence of fossil remains and land-locked vertebrates
• Convection currents


  Circular currents in the mantle caused by the magma being heated by the core off the Earth.

  Can split and move the crust
• Ridge push


  when the force of gravity moves a plate downward and away from a ridge
• Slab pull


  the pulling of a tectonic plate as its edge subducts deep into the mantle