Plate Boundaries

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Destructive (Convergent)

Movement of Plates

  • Convection currents move towards each other 
  • Oceanic plate is forced downwards into the mantle, becuase it is more dense, forming a 'subduction zone'
  • Deep trench is formed where the plate it forced downwards
  • Continental plate forced up into mountain range
  • Oceanic crust begins to melt as it goes into the mantle - hotter nearer the core
  • It then floats back up because it becomes less dense
  • When material floats back up magma erupts back to the surface creating volcanes

Activity 

  • Both earthquake and volcanic activity
  • Volcanic activity due to magma - huge/powerful - due to fiction and pressure 

Example

Nazca Plate (oceanic ) and the South American Plate (continental)

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Destructive (Convergent) Diagram

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Conservative (Transform)

Movement of Plates

  • Convection currents are moving past each other (sliding)
  • One plate moves in one direction as the other goes in the opposite direction 
  • A gap is created behind each of the plates as it moves forward and this is called a fault
  • Along the 'meeting point' a fault line is created where huge friction is caused resulting in a earthquake
  • Plates get stuck so pressure builds and builds until eventually they suddenly jerk forwards
  • Pressure is relseased and an eathquake occurs

Activitiy

  • Earthquake activity only - more pressure the higher the magnitude of the earthquake

Example

Pacific and North American plates along the San Andreas Fault

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Conservative (Transform) Diagram

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Collision (Convergent) - Two Continental Plates

Movement

  • Convection currents move towards each other
  • When a continental plate meets another continental plate, collide, neither can subdut the other becuase they both have the same density
  • Plates are being forced together at great pressure so the rocks crumble together and form massive mountain chains - fold mountains

Activity

  • Pressure builds up along the plate boundary until the plates jump forward, causing earthquakes to occur

Example

Himalayes - Indian Austalian plate and the Eurasion plate

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Collision (Convergent) Diagram

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Constructive (Divergent)

Movement

  • Convection currents move away from each other
  • This pulls the plates away from each other
  • Pressure that has bulit up is released
  • As a 'gap' appears between the plates then lava can easily escape either in the form of relatively gentle eruption or as lava flow
  • The lava creates and new oceanic crust and forms a mid ocean ridge

Activity

  • Volcanic activity - lava = outside volcano - magma = inside volcano
  • Plates are moving so some tremours - earthquake activity

Example

Mid Atlantic Ridge

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Constructive (Divergent) Diagram

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