Natural Hazards and climate change

• Natural Hazard


  An extreme natural event that threatens property and human life
• Factors That Affect Risks


  • Wealth
  • Population Density
  • Geographical Location
• Wealth


  How rich or poor a country is will affect how well it prepares for a hazard, and how it is able to cope with the effects of a hazard
• Population Density


  Areas that have high population densities (e.g. urban areas) are more likely to be severely impacted
• Geographical Location


  The location of a place (e.g. close to a volcano) influences the risks that hazards pose
• Types of Hazards


  • Geophysical hazards
  • Atmospheric hazards
  • Hydrological hazards
  • Biological hazards
• Geophysical hazards


  • Caused by movements of the earth
• Geophysical hazards


  • Earthquake
  • Volcanic eruption
  • Tsunami
  • Landslide
• Atmospheric hazards


  • Weather related disasters
• Hydrological hazards


  • Caused by water movement
• Biological hazards


  • Caused by living organisms
• Biological hazards


  • Disease epidemic
  • Insect plague
• The Earth's surface is divided into different sections called tectonic plates
• Earthquakes and volcanoes are tectonic hazards (caused by movement of the Earth) and happen at plate margins (where two plates meet)
• Not everywhere in the world is at risk of tectonic hazards
• Places near plate margins are more at risk than others
• There is a pattern of earthquakes and volcanoes occurring in lines where tectonic plates meet
• Ways tectonic plates can move


  • Move apart
  • Move towards each other
  • Move side by side
• Convection currents in the mantle


  Move the tectonic plates
• Ridge push/ slab pull


  Heavier oceanic crust sinks into the mantle, pulling the plate downwards
• Global Atmospheric Circulation


  The process that redistributes heat around the world
• Atmospheric Circulation Cells


  • Hadley Cell
  • Ferrel Cell
  • Polar Cell
• Hadley Cell


  Hot air rises at the equator (low pressure) and moves towards higher latitudes before sinking at the tropics (high pressure)
• Ferrel Cell


  Warm air travels towards the poles, it meets the cold air from the pole at 60° forming depressions (air rises)
• Polar Cell


  The polar cell has air sinking at the poles (high pressure) and flowing back towards the Ferrel cell
• Climate Zones


  • Hot and wet
  • Sub-tropical high pressure belt
  • Sub-polar low pressure belt
  • Cold and dry
• Hot and wet climate


  Concentrated solar radiation creates a hot climate. Hot air rises, creating low pressure. It cools and condenses to give predictable convectional rainfall
• Sub-tropical high pressure belt

  Sinking air loses moisture, giving clear blue skies, and little precipitation. It is hot because it is still quite close to the equator.
• Sub-polar low pressure belt


  Air moving north in the Ferrel cell is forced up when it meets cold air from the Polar cell. It cools and condenses, giving frontal rainfall
• Cold and dry climate


  The sun's radiation is spread-out over a large area, making it cold. Sinking air in the Polar cell gives high pressure and dry weather.
• Tropical Cyclone


  Large rotating storms that form over the oceans in tropical areas. Depending on where in the world they form, they are known as hurricanes (Atlantic Ocean), cyclones (Indian Ocean) or typhoons (Pacific Ocean).
• Tropical Cyclone


  • Easily identifiable due to the calm eye in the centre of the storm and the eye wall surrounding the eye. High density cloud covers the remaining area of the storm.
• Distribution of Tropical Cyclones


  Develop over tropical and subtropical oceans between the Tropic of Cancer and the Tropic of Capricorn (between 5 and 30 degrees latitude). Need a water temperature of over 27°C to be able to form. Needs to be a rotational force (the Coriolis effect), therefore areas immediately around the equator do not experience tropical cyclones.
• Frequency of Tropical Cyclones


  Usually form towards the end of summer and in the autumn due to the specific conditions required.
• Formation of Tropical Cyclones

  1. A source of moist, warm air over 27 °C

  2. The season when the ocean is at the warmest (towards the end of summer and into the autumn)

  3. Winds converging at the ocean surface, causing the air to rise.

  4. Between latitudes 5° and 30° north and south of the equator. This is because this is where the Coriolis effect can cause the rotation of air.
• The path of a cyclone is known as its track
• Saffir-Simpson Scale


  Used to measure the intensity of hurricanes
• Types of Vulnerability


  • Physical
  • Economic
  • Social
• Physical Vulnerability


  Steep slopes increase the risk of landslides.

  Areas where tropical storms form are hit more frequently as they are in the path of the storm.

  Low-lying coastlines are vulnerable to storm surges, flooding and high winds.
• Social Vulnerability


  In developing countries, buildings tend to be of poorer build quality and easily damaged.

  Harder to rescue people if infrastructure is damaged or is non-existent in some poorer countries.

  Health and well-being are impacted regardless of wealth, but poorer countries struggle to treat injuries and provide basic support.