tectonics

• what are the two types of crust

  • oceanic (thin, dense)
  • continental (thick, less dense)
• what is an earthquake


  • a sudden and violent period of ground shaking commonly cause by a sudden movement of rocks within the Earth's crust
• what happens at a constructive plate margin?


  • two plates move apart
• what happens at a destructive plate margin?


  • two plates move towards each other
• what happens at a conservative plate margin?


  • two plates are sliding alongside one another
• why do tectonic plates move?


  • Convection currents from deep within the Earth
• what is a volcano?


  • a large and often conical shaped landform usually formed over a long period of time by a series of eruptions
• what type of rock are volcanoes fed by?


  hot molten rock
• what are four ways that the risk of tectonic hazards can be reduced?


  • prediction
  • monitoring
  • protection
  • planning
• what are examples of monitoring volcanoes?

  • seismicity- seismographs record earthquakes
  • remote sensing - satellites detect heat and changes to the volcano's shape
  • geophysical measurements - detect changes in gravity as magma rises to the surface
  • gas - instruments detect gases released as magma rises
• how can the flow of volcanoes be diverted?


  • earth embankments
  • explosives
• what are examples of ways buildings have been protected from earthquakes?

  • walls reinforced
  • automatic shutter
  • shock absorbers
  • reinforced foundations
• how can hazard maps be used in planning?


  • can be used to restrict certain land uses
  • identify areas needed to be evacuated when an eruption is about to happen
• describe the process of a destructive plate margin

  • two plates meet - the denser(oceanic) plate is subducted under the less dense plate
  • Friction between the two plates causes earthquakes
  • the oceanic plate melts as it moves downwards
  • magma is created - breaks through the surface to form volcanoes
• describe the process of a destructive plate margin when two continental plates meet

  • two plates collide and crust becomes crumpled and uplifted
  • fold mountains formed (himilayas)
  • earthquakes during the mountain building process
  • no volcanoes - no magma