hazards

• A hazard is a potential threat to human life and property caused by an event
• Hazards can be human-caused or occur naturally (natural hazards)
• An event becomes a hazard when it is a threat to people
• Degg’s model represents the concept of hazards
• Three major types of geographical hazards:

  • Geophysical hazards caused by land processes, mainly tectonic plates (e.g. volcanoes)
  • Atmospheric hazards caused by atmospheric processes and conditions (e.g. wildfires)
  • Hydrological hazards caused by water bodies and movement (e.g. floods)
• Hazards can be a mixture of geographical processes, e.g. a tropical storm as a hydrological-atmospheric hazard
• People have different viewpoints on hazards and risks based on lifestyle factors like wealth, experience, education, religion, beliefs, and mobility
• Wealth influences how hazards are perceived, with wealthier individuals having different perceptions of risk
• Experience with hazards affects understanding and perception of future hazards
• Education about hazards helps in understanding their effects and potential devastation
• Religion, beliefs, and mobility also influence how hazards are perceived
• Human responses to hazards can be passive (fatalism) or active (prediction, adaptation, mitigation, management, risk sharing)
• Fatalism is the belief that hazards are uncontrollable natural events and losses should be accepted
• Active responses include prediction, adaptation, mitigation, management, and risk sharing strategies
• Incidence refers to the frequency of a hazard, not affected by its strength
• Distribution indicates where hazards occur geographically
• Intensity is the power of a hazard, while magnitude is the size of the hazard
• Level of development affects how a place can respond to a hazard, with economic development influencing the effectiveness of mitigation strategies
• The Park Model represents human responses to hazards, showing the steps in recovery after a hazard
• The Hazard Management Cycle outlines stages of responding to events, including preparedness and response
• Stages of responding to events:

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

  • Hazard models are useful but less effective due to the unpredictability of hazards
  • Questions to evaluate effectiveness of models:
  • Can they be applied to every hazard?
  • Does the model take aspects of hazards into account such as the level of development?
  • Is there any timeframe considered?
  • Could the model be less vague and include more steps that can be applied to all hazards?
  • Does the model present hazards currently and account for hazards affected by climate change?
• Plate Tectonics:

  • 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 rock, asthenosphere is semi-molten magma
  • Lithosphere: Broken up into plates, crust is the top layer
  • Crust: Thin top layer of lithosphere
  • Plate tectonic theory:
  • Lithosphere broken up into tectonic plates
  • Plates move due to convection currents in the asthenosphere
  • Plate boundaries where plates meet
• Different Plate Boundaries:

  • Destructive plate boundaries:
  • Continental and oceanic interactions
  • Oceanic and oceanic interactions
  • Continental and continental interactions
  • Constructive plate boundaries:
  • Oceanic and oceanic interactions
  • Continental to continental interactions
  • Conservative plate boundary
  • Hotspots
• Volcanic Hazards:

  • Lava flows
  • Lahars (mudflows)
  • Glacial floods (jökulhlaups)
  • Tephra
  • Toxic gases
  • Acid rain
  • Nuées ardentes/pyroclastic flows
• Spatial Distribution:

  • Along constructive or destructive plate boundaries, or located on hotspots
  • The Ring of Fire
  • Magnitude of Vulcanicity measured using the Volcanic Explosivity Index (VEI)
  • Frequency of eruptions
  • Regularity and predictability of volcanic eruptions
• Type of Volcanic Hazard:

  • Environmental, economic, social, and political effects
  • Primary and secondary effects
  • Responses to volcanic hazards
• Hazards can be responded to by:

  • Preventing them directly
  • Being prepared for the next hazard
  • Mitigating the effects
  • Completely adapting your lifestyle to limit the hazard’s effects
• Plates do not perfectly fit into each other, causing them to not move in fluid motions
• At plate boundaries, plates can become stuck due to the friction between plates
• When plates are stuck, convection currents in the asthenosphere continue to push, building pressure until the plates eventually give way
• The pressure release causes a jolting motion in the plates, leading to seismic movement spreading throughout the ground in the form of seismic waves
• The focus is the point underground where the earthquake originates from, while the epicentre is the area above ground directly above the focus
• The Ring of Fire accounts for 90% of the world’s earthquakes, while the Alpine-Himalayan belt accounts for 5-6% of the world’s earthquakes
• Seismicity is measured using the logarithmic Richter Scale and the Modified Mercalli Intensity Scale
• The magnitude of an earthquake is dependent on the depth of focus
• Earthquakes are frequent around the world and occur every day at boundaries
• Earthquakes follow no pattern and are random, so there is irregularity between events
• Earthquakes are almost impossible to predict, with microquakes giving some indication but the magnitude being unpredictable
• Hazards caused by seismic events include:

  • Shockwaves (seismic waves)
  • Tsunamis
  • Liquefaction
  • Landslides and avalanches