Tectonic Hazards

• The earth is made up of the inner core, outer core, mantle and crust
• State the two types of crust and their characteristics

  • Oceanic crust - Thin, denser and younger
  • Continental crust - Thick, less dense and older
• Explain why continental crusts are older than oceanic crusts

  Oceanic crust is continuously being created and destroyed through plate movements. This is when the denser oceanic crust subducts below the lighter continental plate
• State what the tectonic plate theory says about the movement of plates

  Tectonic plates move because of convection currents that are created by the magma moving
• Where a plate meets is known as a plate boundary or plate margin
• Explain the distributions of volcanoes and earthquakes

  Volcanoes happen only at constructive and destructive plate margins while earthquakes happen at all plate margins
• Excluding plate margins, where else can volcanoes form and why?

  At hotspots - these are areas where the crust is very thin and magma breaks through the middle of the plate and travels up to the surface as lava
• Explain how volcanoes can form at constructive plate margins

  Constructive plate margins move apart and magma rushes to take its spot. Volcanoes form in places where lava runs out. This lava is usually runny and free flowing
• Identify a constructive plate margin

  Here, plates move away from each other. When pulled apart, magma rises in between the gap left by the absence of two plates and lava pours out to its surface
• How is new land constructed in constructive plate margins?

  By seafloor spreading. This is when new land is formed on the ocean bed. When lava cools, rocks are formed and this eventually leads to it building up and forming new islands
• What do constructive plate margins do to continental crusts?

  On continental crust, these plate margins cause huge fractures to form and create rift valleys. An example of this is the East African Rift Valley
• Identify a destructive plate margin

  Plates here move toward each other. The more dense plate subducts beneath the lighter plate and gets destroyed
• Explain how volcanoes and earthquakes are formed in destructive plate margins

  1. The denser oceanic crust subducts beneath the lighter continental crust
  2. The subducting plate forms an ocean trench and friction between the two plates causes strong, deep earthquakes
  3. Oceanic crust melts as it gets pulled deep into the mantle and creates magma which causes pressure to build up under the crust
  4. The magma pushes out through the crust and creates volcanoes as well as a volcanic island chain
• Explain how fold mountains are created in destructive plate margins

  When two continental plates move toward each other, neither one can subduct below so pressure builds up between the collision of the two plates and the crust is forced upwards which causes fold mountains to form
• Identify a conservative plate margin

  Here, plates move past each other and causes friction to build up between the plates. Eventually, the pressure becomes so large that the plates move in a sudden jolt which releases lots of energy as seismic waves and causes earthquakes
• Explain why no volcanoes are formed at conservative plate margins

  No volcanoes are formed because no magma is generated
• Explain what happens to continental and oceanic crust on conservative plate margins

  On oceanic crust, the friction of the conservative plates moving past each other can cause huge amounts of pressure to be released and displace water, causing tsunamis. On continental crust, this can lead to ground to crack and form fault lines
• What is the difference between a primary effect and a secondary effect?

  A primary effect is an effect caused directly by the hazard itself while a secondary effect is an effect that is the result of the hazard occurring
• State the primary effects of volcanoes and earthquakes

  • Volcanic ash causes respiratory diseases and contaminates water supplies and crops
  • Buildings, homes and school gets destroyed
  • People get injured and killed
  • Transport routes damaged
  • Electricity lines destroyed
• State the secondary effects of volcanoes and earthquakes

  • Lava from volcanoes can melt snow or ice and cause lahars to form
  • Avalanches, landslides and tsunamis can form due to earthquakes
  • Aid can take a long time to arrive due to damaged transport routes
  • Post-disaster famine occurs
• Label the diagram of the earth

  A) Crust

  B) Mantle

  C) Outer core

  D) Inner core

  
• What is meant by immediate response and long-term response?

  Immediate responses are actions taken as soon as the hazard happens and in its immediate aftermath; long-term responses are actions taken after the immediate responses have been sent when effects of the disaster has been minimized
• Give some examples of immediate responses to tectonic hazards

  • Financial aid
  • Creating shelters
  • Donating food, water and clothes
  • Clearing roads to gain access to isolated areas and deliver rescue trucks
• Give some examples of long-term responses to tectonic hazards

  • Insurance payouts
  • Housing reconstruction
  • Making safer infrastructure
  • Reopening of touristic areas to boom the economy
  • Creating warning sirens