The structure of the Earth

Crust
1. Constantly moving
  1. The theory of this constant movement is called plate tectonics
2. Continental/Sial
  1. Silica and Aluminium
  2. Granitic rocks
  3. Average 35-40 km thick can be up to 70 km under mountains
  4. Cannot be subducted, it 'floats'
  5. 30-40% of total crust
  6. Under large land masses or continental shelves or certain shallow seas
    1. The continental shields are the world's oldest rocks e.g. North America and Australia
  7. formed off continental and oceanic crust and are permanent
  8. where it is covered by ocean it is known as an continental shelf
3. Oceanic/Sima
  1. Silica and Magnesium
  2. 60-70% of the total crust
  3. Basalitic lavas
  4. Subducted
    1. Destroyed and recycled at subduction zones
      1. At deepest, 1200 degrees celcius
Mantle
1. Boundary between crust and mantle is called the Mohovoriaic discontinuity 'Moho'
2. Iron, Magnesium and silicate rocks
3. 25 to 70 km below the surface
4. Lithosphere - top 'also includes the crust
5. Asthenosphere - lower mantle is semi-molten
6. At base temp reaches up to 5000 degrees celcius
  1. High temp helps generate convection currents which drive plate tectonics
    1. The theory of the constantly moving crust
Core
1. Boundary between Mantle and core is called the Gutenberg discontinuity
2. Outer core - semi-molten
3. Inner core - solid
  1. 5500 degrees celcius at very centre of the Earth
4. Iron and Nickel
4 concentric layers
1. Shapes, usually circles, that share the same centre point
Discovered through studying other natural events
1. Earthquake wave paths
2. Volcanic eruptions and the material brought up from the Earth

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The structure of the Earth

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