plate tectonics

• Plate tectonics are: the movement of the Earth's lithospheric plates in motion & are responsible for the formation of major landforms.
• Plate boundaries: There are 4 types; Convergent, divergent, conservative and collision. They are physical properties of tectonic plates, between each plate remains a boundary which are belts of major earthquakes.
• What are the 3 mechanisms of plate movement?

  • Ridge push
  • Convection drag
  • Slab pull
• Ridge push: The intrusion of magma into the spreading ocean ridges, such as the Mid-Atlantic Ridge propelling plates apart.
• Convection drag: Convection currents in the plastic mantle, that drag overlying llitosphere.

  Convection drag: Convection currents in the plastic mantle, that drag overlying lithosphere.

  Heat is from radioactive decay in the mantle.

  The cooling and descending parts of the cells are at the subduction zones.
• Slab pull: Colder, denser oceanic litospheric plates descend and pull the remaining plate with them as a result of gravity.

  Occuring in some places, like the Aleutian Trench.
• Convergent: type of stress affecting the area = Compression -> <-

  
  

  Where material is being destroyed/subducted & the plates are moving in unison.

  C-O

  O-O

  C-C
• Divergent: type of stress affecting the area = Tension <- ->

  
  

  Where material is being added & the plates are separating. Features = Earthquakes, Volcanoes, Rift valleys, Ocean ridge, Sea floor spreading, Fracture zones.

  
  

  E.g Carlsberg Ridge in the Indian Ocean & the Mid-Atlantic Ridge equal to 1/3 the width of the ocean.
• Conservative: type of stress affecting the area = Shearing -> <-

  Where plates slide against each other, with no material being added to or subducted from either side.
• Collision: type of stress affecting the area = Compression -> <-

  Where 2 continental plates meet & subduction has ceased.