Unit 1- Natural Hazards

• Natural Hazards


  Extreme geophysical events that have the potential to cause serious material damage and loss of life.

  
• Natural Disasters


  Is only declared when there has been material damage or loss of life.

  
• Hazard Zones


  Term used to identify areas at risk of being affected by a hazard, and to indicate which areas are at greater or lesser risk (vulnerability).

  
• Risk management


  Ways to prevent or mitigate the risk or its effects based on the known consequences of the hazard.

  
• Types of Natural Hazards

  Atmospheric, Geological, Geomorphic, Climatological & Hydrological

  
• 4 Earths Spheres

  1. LIthosphere

  2. Atmosphere

  3. Hydrosphere

  4. Biosphere

  
• Geological Hazard


  Originates within the Earth (earthquakes, volcanic eruptions, tsunamis)
• Types of plate boundaries

  converging, diverging, transform

  
• Earthquakes


  Sudden movements of Earth's crust followed by a series of shocks. Caused by abrupt release of strain accumulated over time.

  
• Earthquake processes

  Focus --> epicentre --> seismic waves --> fault --> plates

  
• P & S waves

  P- fastest waves that travel through the earth

  S- largest amplitude and carry most energy although slower

  
• How is magnitude determined?


  From the strength of seismic waves detected

  
• Ways of measuring earthquakes

  Magnitude --> Richter scale

  Intensity --> Mercalli scale

  
• Diff between Richter + Mercalli

  Richter: compares amount of energy released from earthquake using numbers on logarithmic scale

  Mercalli: value assigned to specific location based on how people were affected/how much structural damage occurred.

  
• What is a tropical cyclone/typhoon/hurricane?

  An intense circular storm that originates over warm tropical oceans + characterised by low atmospheric pressure, high winds, and heavy rain.

  
• What are cyclones called in different areas

  cyclone= western South Pacific

  hurricane= North Atlantic Ocean + eastern North Pacific

  typhoon= western North Pacific
• How do cyclones form?

  -> Ocean water warmed to critical 27

  -> warm air rises in thermals creating low pressure at centre

  -> condensation, clouds form, air unstable

  -> cool air sinks back creating eye

  -> air rushes in from high pressure areas to lpa at centre

  -> storm rotates due to earths spin
• Vulnerability


  Determined by physical, social + economic + environmental factors which increase susceptibility of community, assets or system to the impacts of a hazard

  
• Hazard Prep

  • Know hazard prone areas, monitor news, eduacte public
  • Avoid affected areas
  • Only leave evactuation site if safe, watch for possible flashfloods, check for damages
• Global Patterns of Cyclone

  • Air spirals in toward the centre in a counter-clockwise pattern in both hemispheres
  • Form in deep tropics
  • Slowly drift towards W/SW
  • area vulnerability + motion due to general circulation of Earth's atmosphere
• How do storm surges increase impact of cyclones?

  • Accompany cyclones as they come ashore
  • Pushes water several kms inland
  • Knock down buildings, wash away roads & run ships aground
• How can climate change affect severity of hazards?

  • Sea level rise
  • Water vapour evaporated- more storms
  • Droughts
• MEDC's

  -more economically developed-satisfactory gnp

  -adequate living conditions

  -low births/deaths
• LEDC's

  -less economically developed- poorer gnp

  -high births/deaths

  -inadequate housing
• Risk=hazard x vunerbility x exposure
• Diff ways dealing with risk

  1. risk transfer
  2. risk acceptance
  3. risk avoidance
  4. risk reduction
• Who suffers worst from disasters?

  • generally poor who tend 2 suffer worst
  • economic pressures force people to live in unsafe locations
• What makes people vulnerable?

  Concerns wider environmental & social conditions that limit people + communities to cope with impact of hazard
• Factors that Influence Vulnerability

  physical-poor construction, unregulated land use planning

  economic-dependence on single industries, uninsured formal sectors

  social-poverty, inequality, social exclusion

  environmental-poor management, climate change, overconsumption natural resources
• Earthquake spatial pattern

  -generally occurs along continental plates

  -pressure so great plates break loose -> energy released
• What causes a tsunami

  Triggered by underwater earthquake