SECTION A CHALLENGES OF NATURAL HAZARDS

• Natural hazards

  Sudden, severe events which make the natural environment difficult to manage. They disrupt human life, and have huge economic and social impacts.
• Main types of natural hazards

  • Floods
  • Tropical storms
  • Earthquakes
  • Droughts
• Natural disasters occur where death and destruction result from natural hazards
• As populations grow, so does hazard risk
• Factors increasing hazard risk

  • Urbanisation - densely-populated urban areas concentrate those at risk
  • Poverty - expense of housing leads to building on risky ground
  • Farming - the attraction of nutrient-rich floodplains puts people at risk
  • Climate change - global warming raises sea levels and generates more extreme weather
• The number of earthquakes or volcanic eruptions is not changing, so why are more people at risk from natural hazards?
• Earthquake

  A sudden, violent period of ground-shaking
• Tectonic plates

  The Earth's crust is split into seven major and several minor tectonic plates
• Plate movement and tectonic activity at plate margins

  Cause earthquakes and volcanoes
• Types of plate margins

  • Constructive
  • Destructive
  • Conservative (transform)
• Constructive plate margins

  • The two plates move apart and magma forces its way to the surface, causing mild earthquakes and shield volcanoes
• Destructive plate margins

  • The dense oceanic plate is subducted beneath the less dense continental plate, causing strong earthquakes and composite volcanoes
• Conservative (transform) plate margins


  • The two plates move past each other at different rates, causing powerful earthquakes but no volcanoes
• Plate margins run through densely populated regions such as Japan and southern Europe
• Benefits of tectonic activity in Iceland

  • Geothermal power generation
  • Tourism industry
• Strategies for reducing risks from tectonic hazards

  1. Monitoring

  2. Prediction

  3. Protection

  4. Planning
• Monitoring volcanoes

  • Remote sensing, seismicity, ground deformation
• Monitoring earthquakes

  • Microquakes, ground bulging, raised groundwater levels
• Accurate earthquake prediction is impossible due to lack of clear warning signs
• Global atmospheric circulation

  Interconnected circular air movements called cells, driven by rising and sinking air
• Global atmospheric circulation

  Drives the world's weather
• Weather in the UK

  • Cloudy and wet, as cold polar air meets warm subtropical air
• Weather in deserts

  • Hot and dry, as sinking air creates high pressure
• Weather at the Equator


  • Hot and sweaty, as rising air creates low pressure and heavy rain
• Tropical storm

  Huge storms called hurricanes, cyclones and typhoons in different parts of the world
• Where tropical storms form

  • 5-15 degrees north and south of the Equator, in summer and autumn, where ocean temperatures are highest
• How tropical storms form

  Triggered by the upward movement of evaporated air and moisture, they gather strength drifting over the ocean surface but weaken over land
• Where tropical storms form

  • 5-15 degrees north and south of the Equator, in summer and autumn, where ocean temperatures are highest (above 27°C)
• How tropical storms form

  1. Rising air draws evaporated water vapour up from the ocean surface which cools and condenses to form towering thunderstorm clouds

  2. The condensing releases heat which powers the storm and draws up more water vapour

  3. Multiple thunderstorms join to form a giant rotating storm

  4. Coriolis forces spin the storm at over 120km/h (75mph) creating a vast cloud spiral with a central calm eye of rapidly descending air

  5. Prevailing winds drift the storm over the ocean surface like a spinning top, gathering strength as it picks up more and more heat energy

  6. On reaching land the energy supply (evaporated water) is cut off and the storm will weaken
• Structure of a tropical storm

  • Central eye - small area where relatively cold air sinks towards the ground and warms up, no clouds and calm conditions
  • Eye wall - bank of cloud with strong winds of up to 120km/h, heavy rain, thunder and lightning
  • Beyond the eye wall - further bands with thunderstorms and occasionally tornadoes, strong gusty winds and heavy rain
• Climate change and tropical storms

  • Sea surface temperatures in the Tropics have increased by 0.25-0.5°C
  • Tropical storms may extend into the South Atlantic and parts of the sub-tropics in the future
  • Tropical storms may become more powerful (as measured on the Saffir-Simpson scale)
  • In the North Atlantic, six of the ten most active years since 1950 have happened since the 1990s
  • In the North Atlantic, hurricane intensity has risen in the last 20 years
  • Currently there is no clear evidence that the numbers or intensities of storms are increasing - more data is needed over a longer period of time
• Typhoon Haiyan


  One of the strongest Category 5 storms ever recorded
• Typhoon Haiyan had very low air pressure which caused a 5m storm surge swept on shore by winds up to 275km/h (170mph)</b>
• Coastal devastation included 90% of Tacloban destroyed by storm surge
• Primary effects of Typhoon Haiyan

  • 6300 deaths - most in storm surge
  • Over 600,000 displaced
  • 40,000 homes destroyed or damaged
  • Wind damage to buildings, power lines and crops
  • Over 400mm of rain caused widespread flooding
• Immediate responses to Typhoon Haiyan

  • Rapid overseas aid included NGOs
  • US helicopters assisted search and rescue, and delivery of aid
  • Field hospitals helped injured
  • Over 1,200 evacuation centres set up
• Secondary effects of Typhoon Haiyan

  • 14 million people affected including 6 million jobs lost
  • Flooding caused landslides - blocking roads and restricting access for aid workers
  • Shortages of power, water, food and shelter leading to outbreaks of disease
  • Infrastructure including schools destroyed
  • Looting and violence in Tacloban
• Long-term responses to Typhoon Haiyan

  • UN and international financial aid supplies and medical support
  • Rebuilding of infrastructure
  • Rice farming and fishing quickly re-established
  • Homes rebuilt in a more cyclone-resistant way
  • More cyclone shelters built
• Tropical storms cannot be prevented, but they can be monitored and their tracks predicted
• Developments in technology including satellite tracking allow prediction maps to be prepared and warnings issued