Plate tect

• plate tectonic theory:

  • earth has a 3 layered structure
  • lithosphere is broken up into huge pieces called tectonic plates, which are constantly moving
  • plate movement result in the formations of landforms and phenomena
• Earth's internal structure:

  • core 
  • mantle 
  • oceanic and continental crusts
• Crust:

  • less than 1% of earth's volume
  • outermost layer
  • thickness: 6 - more than 70km
  • continental and oceanic crust
  • broken into many parts called tectonic plates 
• Mantle:

  • 80% of earth's total volume
  • lies above the core
  • thickness: 2900km, mostly solid rock but flows under high temperature and pressure
  • 1000 C - 3700 C
  • Lithosphere: Crust and upper mantle, floats on the softer asthenosphere. Rocks melt to form magma (hot molten rock)
  • Asthenosphere: 'weak' sphere. plastic flowing rocks/ viscous rocks/ sticky and flowing -> rocks are close to their melting point due to high temperature and pressure
• Core:

  • Inner core: ~ 1400 km thick, solid due to extreme pressure exerted
  • Outer core: ~ 2100 km thick, liquid layer
  • thickness: 3300 ~ 3500 km
  • centre of the earth
  • composed mostly of iron and nickel
  • 4400 - 6000 C
• tectonic plate:

  • a crust either oceanic, continental or a combination of both that is broken into different slabs/pieces that move in relation to one another
  • Oceanic crust:
  • dense, consists of geologically young compact heavy and fine grained rock called basalt
  • formed through rapid cooling of magma
  • found beneath deep ocean
  • Continental crust:
  • less dense than oceanic crust
  • consist of geologically old, light and coarse grained rock called granite
  • formed through slow cooling of magma
  • found beneath land masses, under shallow seas near continents
• movement of tectonic plates:

  • convection currents, movement of heat within the mantle
  • material is heated by the core, cause mantle material to expand, rise and spread out beneath plates
  • causes plates to be dragged along, move away from each other, creating a divergent plate boundary
  • hot mantle material loses heat and cools, sinks towards core, pulling plates along, creating a convergent plate boundary
  • sinking mantle material heats up again as it nears the core, process repeats