Hazards

• Hazard


  Something that is a potential threat to human life or property
• Types of natural hazards

  • Geophysical hazards (land processes) e.g. earthquakes, volcanoes, landslides, tsunamis
  • Atmospheric hazards (climate) e.g. cyclones, storms, droughts, hot/cold extremes, wildfires
  • Hydrological hazards (water) e.g. floods, avalanches
• Disaster


  When the hazard seriously affects humans
• Risk


  The likelihood that humans will be seriously affected by a hazard
• Vulnerability


  How susceptible a population is to the damage caused by a hazard
• Factors affecting perception of hazards

  • Wealth
  • Religion
  • Education
  • Past experience
  • Personality
• Responses to hazards


  • Prevent or mitigate the impacts
  • Risk sharing
  • Government coordination
  • Fatalism - accept it cannot be avoided
• Hazard management


  • Depends on hazard incidence, magnitude, intensity, distribution and level of development
  • Hazards of low incidence and high magnitude are the most intense
• Park model


  1. Pre-disaster

  2. Disruption

  3. Relief

  4. Rehabilitation

  5. Reconstruction
• Hazard Management Cycle


  1. Mitigation

  2. Preparedness

  3. Response

  4. Recovery
• Inner core


  A solid ball containing iron and nickel
• Outer core


  Semi-molten and also contains iron and nickel
• Mantle


  Made of silicate rocks
• Crust


  The outer layer
• Lithosphere


  The rigid top part of the mantle and the crust together
• Continental crust


  Thicker (30-70 km) and less dense
• Oceanic crust


  Thinner (6-10 km) and more dense
• Inner core temperature


  6000 degrees
• Mantle temperature


  1000-3500 degrees
• Main source of Earth's heat

  Internal energy, and some left over from when the Earth formed, made of radioactive decay of elements such as uranium
• Tectonic plates


  The lithosphere is divided into slabs that move in relation to each other
• Plate boundaries


  The places where plates meet
• Alfred Wegener came up with the idea of continental drift


  1912
• Harry Hess proposed that the seafloor itself moves and carries the continents with it


  1960
• The theory of paleomagnetism emerged


  1963
• Seismologists measured earthquakes to discover plate boundaries

  Mid 1960s
• Rock samples showed rocks are much younger near the mid-atlantic ridge, and older at the edge of continents


  1968
• Slab pull


  At destructive plate margins, denser crust is forced under less dense crust, causing the sinking of the plate edge to pull the rest towards the boundary
• Ridge push


  At constructive plate margins, magma rises to the surface and forms new crust, which cools and becomes denser, causing gravity to move the denser rock downslope
• Sea floor spreading


  As tectonic plates diverge, magma rises up to fill the gap, then cools to form new crust, which is dragged apart as more new crust forms
• Constructive margin


  Where 2 plates are moving apart, also known as a divergent plate margin
• Processes at constructive margins

  1. Mantle melts due to pressure release, producing magma that rises and can erupt to cause volcanoes

  2. Plates crack due to pressure build-up, causing fault lines and earthquakes
• Constructive margin examples


  • Mid-ocean ridge
  • Rift valley
• Destructive margin


  Where two plates are moving towards each other, also known as a convergent plate margin
• Types of destructive margins

  • Oceanic-continental
  • Oceanic-oceanic
  • Continental-continental
• Conservative margin


  Where 2 plates are moving past each other, causing pressure build-up that leads to earthquakes
• Magma plume


  A vertical column of extra-hot magma that rises up from the mantle, causing volcanic activity that remains stationary as the crust moves
• Volcanic hazards


  • Pyroclastic flows
  • Lava flows
  • Volcanic gases
  • Pyroclastic and ash fallout
• Secondary volcanic hazards


  • Lahars/mudflows
  • Acid rain
• Volcanic explosivity index


  Grades volcanoes from 0-8 based on the amount of material ejected, and how high the material is blasted