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Earthquakes - Coggle Diagram

- - - - Where the ocean crust is being pulled apart and magma rises through the fissures
      - Ocean crust is relatively thin (5km)
      - 5 Oceanic layers:
        
        Settled sediment (ooze)
        
        Pillow basalts
        
        Dolerite dykes
        
        Gabbro
        
        Layered peridotite
    - - Slumping of crustal blocks along normal faults created by tensional forces
      - Splitting of rock due to the pressurised injection of magma
      - Strike slip movement of oceanic crust along transform faults
    - - Usually not very powerful and register 4 or 5 on the Richter scale
      - Earthquakes measuring over 8 have been recorded along transform faults
      - Lisbon earthquake 1755 - mag 7.7
  - - - Compression and crustal movement along reverse or thrust faults in accretionary prism
      - Stick slip motion of oceanic lithosphere in the subduction zone
        
        This is associated with the sudden release of enormous quantities of stress that has built up in subducting plate over 100s of years
        
        If the magnitude exceeds 8, they are known as Mega Thrust Earthquakes
        
        Over time successive earthquakes along the subduction zone reveals an inclined distribution that mirrors the descent of oceanic lithosphere into the mantle
      - Earthquakes are more frequent in the upper part of the subduction zone (0-300km) as the plate is colder and more brittle
        
        Below 300km the plate is warmer and more likely to plastically deform in response to stress
      - Uplift of continental crust along thrust faults
    - - Between a subducting ocean plate and constructive plate
      - Earthquakes vary from shallow (<10km) to very deep (500km)
    - - Metamorphic dewatering
      - Slab pull
      - Composite volcano with basic magma
  - - - Any two plate types moving in the same direction next to each other but at different rates/speeds
    - - Earthquakes here are triggered by the strike slip motion of two plates
    - - Pacific and North American plate along the San Andreas Fault
      - Usually shallow and range in magnitude upto 8