Hazards 1

• Hazard


  A potential threat to human life and property caused by an event
• Major types of geographical hazard

  • Geophysical hazards caused by land processes, majorly tectonic plates (e.g. volcanoes)
  • Atmospheric hazards caused by atmospheric processes and the conditions created because of these, such as weather systems (e.g. wildfires)
  • Hydrological hazards caused by water bodies and movement (e.g. floods)
• Aspects of Hazards


  • Incidence: frequency of a hazard
  • Intensity: the power of a hazard i.e. how strong it is
  • Magnitude: the size of the hazard, usually this is how a hazard's intensity is measured
  • Distribution: where hazards occur
  • Level of development: economic development will affect how a place can respond to a hazard, so a hazard of the same magnitude may have very different effects in two places of contrasting levels of development
• Perception


  People have different viewpoints of how dangerous hazards are and what risk they pose. These perceptions are dependent on lifestyle factors such as economic and cultural factors.
• Human Responses to Hazards

  • Fatalism: The viewpoint that hazards are uncontrollable natural events, and any losses should be accepted as there is nothing that can be done to stop them
  • Prediction: Using scientific research and past events in order to know when a hazard will take place, so that warnings may be delivered and impacts of the hazard can be reduced
  • Adaptation: Attempting to live with hazards by adjusting lifestyle choices so that vulnerability to the hazard is lessened
  • Mitigation: Strategies carried out to lessen the severity of a hazard
  • Management: Coordinated strategies to reduce a hazard's effects. This includes prediction, adaptation, mitigation
  • Risk sharing: A form of community preparedness, whereby the community shares the risk posed by a natural hazard and invests collectively to mitigate the impacts of future hazards
• The Park Model


  1. Graphical representation of steps carried out in hazard recovery

  2. Rough indication of time frame

  3. Can be used in comparing hazardous events

  4. The steepness of the curve shows how quickly an area deteriorates and recovers

  5. The depth of the curve shows the scale of the disaster
• Stages of the Park Model

  • Relief (hours-days): Immediate local response - medical aid, search and rescue. Immediate appeal for foreign aid - the beginnings of global response
  • Rehabilitation (days-weeks): Services begin to be restored. Temporary shelters and hospitals set up. Food and water distributed. Coordinated foreign aid - peacekeeping forces etc.
  • Reconstruction (weeks-years): Restoring the area to the same or better quality of life. Area back to normal - ecosystem restored, crops regrown. Infrastructure rebuilt. Mitigation efforts for future event
• Stages of the Hazard Management Cycle

  • Preparedness: Being ready for an event to occur (public awareness, education, training)
  • Response: Immediate action taken after event (evacuation, medical assistance, rescue)
  • Recovery: Long-term responses (restoring services, reconstruction)
  • Mitigation: Strategies to lessen effects of another hazard (barriers, warning signals developed, observatories)
• Plate Tectonics

  The lithosphere is broken up into large slabs of rock called tectonic plates. These plates move due to the convection currents in the asthenosphere, which push and pull the plates in different directions.
• Structure of the Earth

  • Inner core: Solid ball of iron/nickel. Very hot due to pressure and radioactive decay
  • Outer core: Semi-molten, iron/nickel
  • Mantle: Mainly solid, rocks high in silicon. The top of the mantle is the asthenosphere
  • Lithosphere: Semi-molten, broken up into plates, moves due to convection currents. Majority of the lithosphere is within mantle. The top of the lithosphere is the crust
  • Crust: The thin top of the lithosphere. Oceanic crust is dense and is destroyed by plate movement, continental crust is less dense and is not destroyed.
• Plate Boundaries


  • Destructive plate boundary: Continental and oceanic, Oceanic and oceanic, Continental and continental
  • Constructive plate boundary: Oceanic and oceanic, Continental to continental
  • Conservative plate boundary: Between any crust, the parallel plates move in different directions or at different speeds. No plates are destroyed so no landforms are created.
• Hotspots


  Areas of volcanic activity that are not related to plate boundaries. Hot magma plumes from the mantle rise and burn through weaker parts of the crust.
• Aspects of Volcanic Hazards

  • Spatial Distribution: Along constructive or destructive plate boundaries, or located on hotspots
  • Magnitude: Vulcanicity is measured using the Volcanic Explosivity Index. The more powerful, the more explosive
  • Frequency: Volcanoes are classed as either active, dormant or extinct. An estimated 50-60 volcanoes erupt each month
  • Regularity: Volcanic eruptions are regular in that the eruptions on each type of boundary are similar
  • Predictability: Regularity of eruptions can help estimate when eruptions will take place, but there is no definite predictions
• Volcanic Hazards


  • Lava flows
  • Lahars (mudflows)
  • Floods
  • Tephra - any type of rock that is ejected by a volcano
  • Toxic gases
  • Acid rain
  • Nuées ardentes/pyroclastic flows - clouds of burning hot ash and gas that collapses down a volcano at high speeds
• Effects of Volcanic Hazards

  • Primary: Ecosystems damaged, Wildlife killed, Businesses and industries destroyed or disrupted, People killed, Homes destroyed
  • Secondary: Water acidified by acid rain, Volcanic gases contribute to greenhouse effect, Jobs lost, Profit from tourism industry, Fires can start which puts lives at risk, Mudflows or floods, Trauma, Homelessness, Conflicts concerning government response, food shortages, insurance etc.
• Seismic Hazards


  Plates do not move in fluid motions. At any boundaries, plates become stuck due to the friction between plates. The pressure builds so much that it cannot be sustained and the plates eventually give way. The pressure is released quickly, causing a jolting motion in the plates.
• Aspects of Seismic Hazards

  • Spatial Distribution: Along all boundaries
  • Magnitude: Seismicity is measures using the logarithmic Richter Scale and the Mercalli Scale
  • Frequency: Earthquakes are frequent around the world and occur every day at boundaries
  • Regularity: Earthquakes follow no pattern and are random so there is irregularity between events
  • Predictability: Earthquakes are almost impossible to predict
• Seismic Hazards


  • Shockwaves (seismic waves)
  • Tsunamis
  • Liquefaction
  • Landslides and avalanches
• Effects of Seismic Hazards

  • Primary: Earthquake can cause fault lines which destroy the environment, Liquefaction
  • Secondary: Radioactive materials and other dangerous substances leaked from power plants, Saltwater from tsunamis flood freshwater ecosystems, Economic decline as businesses are destroyed, High cost of rebuilding and insurance payout, Sources of income lost, Gas pipes rupture, starting fires which can kill, Water supplies are contaminated as pipes burst, spreading disease and causing floods, Tsunamis which lead to damaging flooding, Political unrest from food shortages or water shortages, Borrowing money for international aid, Can be initial chaos and 'lawlessness' e.g. looting
• Tropical storm


  A low pressure, spinning storm with high winds and torrential rain
• Conditions for a storm to form

  • Temperature: Ocean temperatures must be around 26 - 27°C to at least 50 metres deep
  • Rotation: Forms around the equator but no less than 5° on either side
  • Air pressure: Must be in areas of unstable air pressure - usually where areas of high pressure and low pressure meet (convergence) - so that warm air rises more readily and the clouds can form
• Saffir-Simpson Scale


  A scale of 1-5 based on wind speed and thus power of the storm
• Tropical storms occur in the Northern Hemisphere from June-November, Southern Hemisphere from November-April
• Tropical storms that are more powerful and reaching land are thought to be increasing in frequency
• Regularity of tropical storms

  Irregular because although they occur in the same areas, their path does not follow a set route - the route taken is dependent on the storm and the climatic conditions
• Tropical storms form away from land meaning satellite tracking of cloud formations and movement can be tracked and the general route can be predicted
• Hazards caused by tropical storms

  • High winds - over 300km/h and therefore very strong
  • Flooding - coastal/river flooding from storm surges and heavy rain
  • Landslides - due to soil becoming heavy when wet with high levels of rain
  • Storm surges - Large rise in sea levels caused by low pressure and high winds, pushing water towards the coast
• Primary effects of tropical storms

  • Beaches eroded
  • Sand displaced
  • Coastal habitats such as coral reefs are destroyed
  • Businesses destroyed
  • Agricultural land damaged
  • Drowning
  • Debris carried by high winds can injure or kill
  • Buildings destroyed
  • Government buildings destroyed
• Secondary effects of tropical storms

  • River flooding/ salt water contamination
  • Animals displaced from flooding e.g. alligators
  • Water sources changing course from blockages
  • High cost of rebuilding and insurance payout
  • Sources of income lost
  • Economic decline from sources of income destroyed
  • Homelessness
  • Polluted water supplies spread disease
  • Food shortages from damaged land
  • Issues paying back international aid
  • Pressure for government to do more about global warming
• Wildfire


  A large, uncontrolled fire that quickly spreads through vegetation
• Conditions favouring intense wildfires

  • Vegetation Type: Thick, close together vegetation allows fires to spread quickly and easily. Trees and thick bushes lead to more intense wildfires; grasslands do not burn as intensely. Vegetation with flammable oils - like eucalyptus - causes more intense fires also
  • Fuel Characteristics: Vegetation should be dry to allow it to catch. Finer vegetation causes fires to spread quicker, but larger, thicker forms of vegetation burns for longer and more intensely
  • Climate and Recent Weather: Must be in a climate that has enough rainfall to have sufficient plant growth , but considerable dry spells and droughts to dry out the fuel. Areas with dry seasons such as California allow for intense wildfires. Wind also causes fires to spread quicker. Recent temperature increases have caused an increase in the number of wildfires
• Fire Behaviour


  Fires spread quickly on hills as the heat rises. Fire can also 'jump' across rivers and into areas due to lit debris which causes it to spread
• Causes of wildfires

  • Naturally: spontaneous combustion, volcanoes and lightning
  • Humans: lit cigarettes, BBQ's, agriculture, train lines and more
• Primary effects of wildfires

  • Air pollution from ash
  • Water pollution
  • Habitats destroyed in fire
  • Toxic gases released in burning
  • Businesses destroyed
  • Agricultural land damaged
  • Cost of fighting fires (firefighters, helicopters, water)
  • People killed or injured in fires
  • Homes destroyed
  • People go missing during evacuations
  • Government buildings destroyed
• Secondary effects of wildfires

  • Removing invasive species and stimulating seed germination
  • Migration patterns of animals affected
  • Increased CO2 from fires could heighten the greenhouse effect
  • High cost of rebuilding and insurance payout
  • Sources of income lost
  • Discouraging visitors, losing tourism sector
  • Planes cancelled
  • Homelessness
  • Food shortages from destroyed agricultural land
  • Health problems such as asthma from smoke inhalation
  • Borrowing money for international aid
  • Pressure for government to do more about global warming due to increased frequency
• Theory of Plate Tectonics

  • The tectonic theory of crustal evolution is a scientific theory that revolutionised people’s understanding and study of geological processes and the Earth
  • It helps to explain geological phenomena such as:
  • the occurrence of hazards such as earthquakes and volcanic eruptions
  • the formation of mountain ranges
  • the movement of continents
  • the distribution of some mineral resources such as diamonds
• Magnitude


  The most common way to measure an earthquake
• Hot spots


  Form around the core of the Earth where radioactive decay is concentrated
• Magnitude


  Measures the energy released at the source (focus)
• Hot spots


  • Extreme heat creates magma plumes
  • Magma plumes are upwellings of superheated rock that rise from deep within the Earth's mantle towards the surface