Structure of the Earth

• Diagram of Earth’s structure

  
• • Earth’s structure model was developed using understanding of seismic waves.
• Path followed by P waves through Earth from epicentre

  
• P WAVES FROM EPICENTRE

  • Paths are curved due to refraction as the waves travel further through each layer , so properties of the rocks (like density) change which changes speed of wave.
• P WAVES FROM EPICENTRE

  • Sudden changes in direction at the boundaries between layers are due to refraction at the boundary, as rocks in different layers = different properties.
• • Tracking paths of P waves through the Earth proved there were layers within the Earth.
• S WAVE SHADOW ZONE

  
• S WAVE PATH

  • Waves still follow a curved path due refraction, but don't cross boundary between the mantle and the outer core - S waves can’t pass through liquids.
• • Proves outer core must be a liquid.