Plate Tectonics

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Plate Tectonics
Revising Earthquakes and Volcanoes
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Aim of todays session

• To revise plate tectonics structure of the earth
  and plate movements
• To know the different plate boundaries
• To understand natural hazards- Earthquakes and
  Volcanoes

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Structure of the Earth

• The earth is made up of different layers
• Inner core
• Outer core
• Mantle
• Crust
• The crust is broken into slabs of varying sizes,
  called Plates
• Crust can be Continental or Oceanic
• A place where two plates meet is called a plate
  boundary

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Convection Currents

• Heat in the centre of the earth sets up
  convection currents in the mantle.
• When they reach the surface the currents move the
  plates.
• Plates can move
• towards each other,
• away from each other,
• pass sideways to each other.
• It is where these plate meet that we find
  earthquakes and volcanoes

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Types of plate margins

• Destructive
• Collision
• Constructive
• Conservative

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Destructive margins

• Where oceanic crust is destroyed
• Oceanic crust moves towards continental crust
  it is forced downwards, where pressure builds.
  The crust is melted, turns into magma and rises
  to the surface.
• Earthquakes
• Volcanoes

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Collision margins

• Two plates collide
• Continental plates move together they cannot
  sink or be destroyed so the land is pushed
  upwards to form high fold mountains
• Earthquakes
• Volcanoes

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Constructive margins

• New land is created or constructed
• Two plates move apart and lava rises to fill the
  gap. New oceanic crust is created.
• Earthquakes
• Volcanoes

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Conservative margins

• Two plates try to slide past each other. When
  the two plates stick, pressure builds, until it
  is finally released
• Earthquake
• Volcano

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Volcanoes

• Can be active
• dormant
• extinct
• Shape is determined by the viscosity of the lava-
  Shield volcano
• Composite volcano
• Eruptions are easier to predict than earthquakes
• What other labels could be added to the
  cross-section of the volcano?

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Earthquakes

Measured on an instrument called a
seismometer. Strength is commonly measured on the
Richter Scale Cannot be accurately predicted so
people try to minimise their damage. How? How
can people be prepared?