Earth structure

• Inner core


  Radius of about 1300 km, solid due to tremendous pressures, pressure 4 million times atmospheric pressure, temperatures up to 7000°C, mostly iron with some nickel
• Outer core


  About 2250 km thick, molten, outer surface has depressions and peaks, temperatures between 4000°C and 6000°C
• Mantle


  Makes up 84% of Earth's volume, partially molten layer surrounding outer core, extends to 2900 km depth, temperatures 1000°C near crust to 3700°C near core, has lower and upper mantle, upper mantle drives plate tectonics
• Crust


  Two types - continental crust (igneous and sedimentary rocks, mostly granite) and oceanic crust (darker, denser rocks like basalts)
• Most common elements in Earth's crust

  • Oxygen
  • Silicon
  • Other elements
• Pangaea


  Supercontinent that split into smaller continents that drifted across Earth's surface over millions of years
• Matching fossil evidence

  • Mesosaurus freshwater reptile
  • Cynognathus land reptile
• Climate evidence for continental drift

  • Warm weather plants and animal fossils in ice-covered regions
  • Evidence of glaciers where they shouldn't be
  • Ice-rafted boulders
  • Coal
  • Low-latitude deserts
  • Evaporite deposits
  • Desert dune deposits
  • Coral reef
• Wegener could not explain the mechanism that drives continental drift, but the theory of plate tectonics was later developed