Tectonics

• Earth's layers


  • Inner and outer core
  • Mantle
  • Crust
• Crust


  • Thinnest layer
  • Two types: Oceanic (thin, dense, basaltic) and Continental (thicker, lighter, granite)
• Core


  • Centre of the Earth
  • Very hot and dense
  • Outer core: Hot, made of iron and nickel
  • Inner core: Hotter, solid ball of iron and nickel
• Lithosphere and Asthenosphere


  • Lithosphere: Crust and top layer of mantle, broken into tectonic plates
  • Asthenosphere: Denser, more mobile layer in upper mantle, allows plate movement
• Mantle


  • Thickest layer
  • Temperature ranges from 1000°C to 3,700°C
  • Upper mantle is mostly solid, slow moving
  • Lower mantle is solid, hotter and denser
• What drives movement in the mantle?

  Convection currents: Rock heated in lower mantle rises, cools and sinks back down
• Tectonic plates


  Large areas of rock that make up Earth's crust, float on asthenosphere and are moved by convection currents
• Types of plate boundaries

  • Convergent (oceanic-continental, continental-continental)
  • Divergent
  • Conservative
• Convergent (oceanic-continental)


  • Oceanic plate subducts beneath continental plate
  • Melting of subducted crust creates magma and volcanoes
• Convergent (continental-continental)


  • No subduction, collision causes folding and faulting to form mountains
  • No volcanism, but major earthquakes occur
• Divergent


  • Plates move apart, asthenosphere melts to form new crust
  • Shield volcanoes and rift valleys form
• Conservative


  • Plates slide past each other, causing earthquakes when they get stuck
• Composite volcano


  • Tall, steep-sided, made of alternating ash and lava layers
  • Andesitic lava is viscous, eruptions are infrequent but violent
• Shield volcano


  • Gently sloping dome, made of fluid basaltic lava
  • Eruptions are frequent and gentle
• Hotspot volcano


  Formed away from plate boundaries by a plume of superheated rock rising through the mantle
• Earthquake


  • Sudden vibrations in Earth's crust caused by rock fracturing along a fault
  • Energy is released in the form of seismic waves radiating from the focus
• Earthquake impacts


  • Depend on magnitude, depth, time of day, population density, preparedness
• Earthquake measurement


  Richter scale (logarithmic) and Moment Magnitude Scale (wider range, more accurate)
• Tsunami


  • Series of giant ocean waves triggered by seafloor displacement from an earthquake
  • Waves move fast in deep water, slow but increase in height near coasts
• Earthquake/volcano preparedness methods


  • Seismometers
  • Hazard maps
  • Satellite monitoring
  • Tiltmeters
  • Earthquake-proof building design
  • Public education
  • Emergency services preparation