Earthquake- Plate tectonic

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Lucid

Cards (21)

  • Earthquakes are tremors or vibrations in the earth's crust.
  • Earthquakes are caused by the movement of the worlds plates.
  • The Theory of Plate Tectonics tells us how the earth's crust is split into a number of sections called plates.
  • Plates float on the semi-molten rock of the mantle.
  • Convection currents in the mantle cause the magma to rise, cool, flow sideways and sink.
  • As a result the plates which float in the mantle are constantly moving.
    • Earthquake activity is associated with the following plate boundaries:
    • Destructive Boundaries
    • Conservative Boundaries
    • Constructive Boundaries
  • At destructive boundaries two plates collide. The heavier plate will be subducted (sink and melt).
  • The sinking plate in destructive boundaries may jam or stick resulting in a huge build up of pressure.
  • Eventually the destructive plates may pull apart at a point in the earth's crust known as the focus.
  • Seismic (shock) waves will radiate out from the focus causing tremors in the earth's crust.
  • The tremors will have most effect at the epicentre a point directly above the focus.
    • Earthquakes at destructive boundaries can be divided into 2 groups:
    • Earthquakes associated with fold mountain building
    • Earthquakes associated with subduction
  • The Japanese Tsunami quake in 2011 occurred at a subduction zone.
  • The Pacific plate was subducted resulting in an earthquake measuring 9.0 on the Richter Scale in the Japanses earthquake
  • The Japanese earthquake triggered a Tsunami which killed approximately 27,000 people.
  • Earthquakes also occur where two continental plates collide and fold mountains are formed.
  • The Himalayas formed as a result of the collision of the Indian and Eurasian plates and this area experiences earthquake activity.
  • Shallow earthquakes are associated with continental-continental collision
  • The focus is less than 70 km deep with continental-continental collisions
  • quakes that make fold mountains are among the most destructive as their focus is so close to the surface.