Structure of the Earth

• Crust


  • Outer shell of the earth
  • Consists of oceanic and continental crust
• Oceanic crust


  • Composed of dense basalt rock
  • Around 5km thick
• Continental crust


  • Consists mainly of granite
  • Less dense than basalt
  • Averaging around 30km thick
  • Can be up to 70km thick in some areas
• Mantle


  • Accounts for more than 80% of the volume of the earth
  • Semi-molten liquid
  • Becomes denser the closer you get to the core
• Core


  • Mostly made up of iron (80%) and nickel (20%)
  • 4 times denser than the crust
  • Provides the earth with its magnetic field
• Outer core


  • Semi-liquid
  • Consists mostly of iron
• Inner core


  • Solid
  • Made from an iron-nickel alloy
• Lithosphere


  • Rigid outer part of the earth
  • Consisting of the crust and upper mantle
• Asthenosphere


  • Below the lithosphere
  • Extends from 100km down to 300km down
  • Semi-molten/viscous
  • Capable of flowing slowly
  • Convection currents exist within
• Mohorovičić discontinuity


  • Boundary between the crust and the mantle
  • Level in the earth where p-waves change velocity abruptly
• Convection currents


  Transfer of heat in a liquid or gas in a circular motion