Topic 1 - Hazardous Earth

• Tropical Cyclone

  A very large, spinning storm that forms in the tropics
• Tropical Cyclones

  • Have high winds and torrential rain
  • Usually affect small islands and coastal regions
• Tropical Cyclones

  • Characterised by low pressure, intense weather and spinning structure
• Formation of a Tropical Cyclone

  1. Warm air rises and creates an updraught, causing an area of low pressure to form

  2. The area inside a tropical cyclone is often as low as 950mb (the pressure on Earth is usually 1013mb)

  3. The centre of the storm, called the eye, can be 15% lower pressure than areas outside of the storm
• Tropical Cyclones

  • Characterised by thunderstorms, strong winds and intense rainfall
  • The area surrounding the centre, called the eyewall contains the strongest winds, thunder and lightning, and torrential rain
  • In very intense storms, sustained winds can reach 240km/hour (150mph), and gusts can exceed 320km/hour (200mph)
• Tropical cyclones rotate due to the spin of the Earth. In the southern hemisphere, the storms spin clockwise; in the northern, anticlockwise
• Tropical Cyclone Structure

  • Warm air ring and rising around the eye
  • Eyewall, with heavy rain, strong winds
  • Eye, calm and cloud free
  • Outer bands, 300 miles wide, can be 1500 miles across
• Names for Tropical Cyclones

  • Hurricane (USA and Latin America/Caribbean)
  • Cyclone (Australia and Madagascar)
  • Typhoon (India, Japan and the Philippines)
• Tropical cyclones need very specific conditions to form, meaning they will only form in certain areas
• Conditions for Tropical Cyclone Formation

  • Ocean temperatures must be around 26 - 27°C and at least 50 metres deep
  • Must be in areas of unstable air pressure usually where areas of high pressure and low pressure meet
  • Winds must be present for the swirling motion to form, but not too strong
  • Tropical cyclones only form around the equator, between 5-15 either side of the equator, but tropical cyclones will not form on the equator
• Tropical cyclones follow certain pathways that are driven by global wind circulation. These pathways are known as the cyclone's track
• Tropical Cyclone Formation

  1. Warm, moist air rises, leaving an area of low pressure below

  2. Warm air from the surroundings moves into this low pressure area and rises too

  3. The warm air cools and condenses to form large thunderstorm clouds

  4. The whole system is spinning due to the Coriolis effect

  5. The constant additions of energy from the warm air causes the storm to spin faster and generate higher wind speeds

  6. The storm develops an eye in the centre, an area of extremely low pressure where cool, dry air descends

  7. Surrounding the eye is the eyewall, the most intense and powerful area of the storm

  8. When the tropical cyclone reaches a coast, the low pressure and high winds will cause a large amount of sea water to be pushed onto the coast, which is called a storm surge

  9. Once the storm reaches land, it no longer has a supply of energy (warm air from the sea) and the eye finally collapses and the storm dissipates
• Physical hazards of tropical cyclones

  • High winds
  • Intense rainfall
  • Storm surges
  • Coastal flooding
  • Landslides
• Tropical cyclones can be very damaging to people, the environment, and the economy
• Primary effects of tropical cyclones

  • People drowned in storm surge
  • Heavy rain causing freshwater flooding
  • Damage to electricity, water, and communications infrastructure (e.g. telephone lines)
• Secondary effects of tropical cyclones

  • Social disorder or conflicts
  • Loss of income as people's livelihoods destroyed
  • Homelessness
  • Strong winds destroying buildings and infrastructure
  • Storm surge damaging buildings
  • Food shortages
  • Crops destroyed
  • Drinking water contaminated
  • Trauma, stress and other mental health issues after the event
  • Spread of disease due to unhygienic conditions
  • Landslides and blocked roads, affecting rescue efforts
• Vulnerability to tropical cyclones

  • Some countries are more vulnerable due to both physical and socioeconomic reasons
  • Higher risk of serious damage in vulnerable countries
• Factors influencing vulnerability to tropical cyclones

  • Education
  • Wealth
  • Poverty
  • Climate change
  • Location
• Education

  Some people are less educated on the risk they face from tropical cyclones, making them unprepared
• Wealth

  Poorer countries may not be able to respond to a tropical cyclone as effectively as a wealthier country
• Poverty

  Can force populations to live in unsafe housing which is not built to withstand tropical cyclones
• Climate change

  • Sea level rise could make people more vulnerable to storm surges
  • Affecting the intensity and distribution of tropical cyclones
• Location


  Those living in tropical cyclone prone areas, especially low-lying coastal areas, are more vulnerable
• Weather forecasting and satellite technology allow for monitoring and predicting the track and intensity of tropical cyclones
• It is possible to predict how high a storm surge will be by analysing the intensity of a storm
• Tropical cyclone management strategies

  • Ensuring the cyclone is monitored using satellites and forecasting technology
  • Having warning systems and evacuation strategies in place
  • Building physical defences to protect the population
• Evacuation routes and safety protocols

  Countries create evacuation routes and warning systems to ensure the population is prepared and alerted
• Raising awareness

  If the community is aware of the risk, they can lower their vulnerability by getting prepared
• Physical defences

  Building and infrastructure design to protect against high winds, storm surges, and flooding
• Having tropical cyclone shelters is important to provide a safe place for people to shelter
• The Earth is separated into layers of different depths and compositions
• Layers of the Earth

  • Inner core
  • Outer core
  • Lower mantle
  • Upper mantle (asthenosphere)
  • Lithosphere
  • Crust
• Inner core


  • Solid ball of iron/nickel under high pressure
  • Radioactive decay generates heat
• Outer core


  • Molten layer of iron and nickel
  • Convection currents transfer heat to the mantle
• Mantle


  • Mainly solid rock, with a semi-molten asthenosphere at the top
  • Convection currents in the asthenosphere move the lithosphere above
• Lithosphere


  • Solid rock that lies on top of the asthenosphere
  • Divided into tectonic plates that move due to convection currents in the asthenosphere
• Crust


  • Top layer of the lithosphere, split into continental and oceanic crust
• Convection currents in the asthenosphere drive the movement of the tectonic plates
• Plate tectonic movement has been happening for hundreds of millions (if not billions) of years, with the continents drifting over time
• Types of plate boundaries

  • Divergent
  • Convergent
  • Conservative