GEOGRAPHY

• Weather can be hazardous
• Global circulation system


  1. Oval movement of air between the Equator and the poles

  2. Air circulates between high and low pressure belts

  3. Winds move from areas of high pressure to areas of low pressure

  4. Winds are part of circulation loops called cells

  5. Cells have warm rising air which creates low pressure belts and cool falling air which creates high pressure belts
• Cells in the global circulation system

  • Hadley cell
  • Ferrel cell
  • Polar cell
• How the global circulation system works

  1. Air rises at the Equator creating a low pressure belt

  2. Air sinks at 30 degrees north and south creating high pressure belts

  3. Warm surface winds move towards the poles

  4. Cool air from the poles moves towards the Equator
• Climate zones


  • Polar climate zone
  • Temperate climate zone
  • Tropical climate zone
  • Subtropics
• Contrasting climates between the UK and Australia

  • Australia is warmer than the UK with hotter summers and milder winters
  • Australia has much lower precipitation than the UK
  • Australia has more extreme winds than the UK
• Tropical storms


  Intense low pressure weather systems bringing extremely strong winds and heavy rain
• Tropical storms develop when sea temperature is 27 degrees or higher
• Condensation when warm air rises and cools releases huge amounts of energy which makes tropical storms powerful
• The Coriolis effect deflects the paths of the wind in tropical storms causing them to spin
• Distribution of tropical storms

  • Occur between 5 and 30 degrees north and south of the Equator
  • Majority occur in the northern hemisphere in late summer and autumn
• The number of tropical storms in the Atlantic has increased since 1984 but there is no overall trend over the last 130 years
• Drought


  A long period where rainfall is below average, causing water supplies to become depleted
• Droughts are often accompanied by high temperatures which increase the rate of evaporation
• The length of a drought is different in different places
• Areas most at risk from drought

  • Central and Southern Africa
  • The Middle East
  • Australia
  • East and South America
  • Parts of North America
• The frequency of droughts has not changed much since 1950, but some scientists suggest they may become more frequent and severe in future due to climate change
• El Niño


  A climatic event in the Pacific Ocean where trade winds weaken or reverse, leading to drought in eastern Australia and flooding in South America
• La Niña


  A climatic event in the Pacific Ocean where trade winds blow with more strength, leading to the opposite effects of El Niño
• The Earth's structure consists of a core, mantle, and crust
• Types of plate boundaries

  • Constructive
  • Destructive
  • Collision
  • Conservative
• Constructive plate boundaries


  1. Two plates moving away from each other

  2. Magma rises from the mantle to fill the gap and cools, creating new crust
• Destructive plate boundaries


  1. Two plates moving towards each other

  2. Denser oceanic plate is forced under the continental plate and destroyed

  3. Creates volcanoes and deep ocean trenches
• Collision plate boundaries


  1. Two continental plates moving towards each other

  2. Neither plate is forced down, instead both plates crumple and fold, forming fold mountains
• Conservative plate boundaries


  1. Two plates moving sideways past each other or at different speeds

  2. Crust is not created or destroyed, but severe earthquakes can occur
• Earthquakes


  • Caused by tension building and being released at plate boundaries
  • Shock waves originate at the focus and are felt at the epicentre
• Volcanic eruptions


  • Occur at destructive and constructive plate boundaries
  • Magma rises through cracks in the crust called vents and erupts onto the surface
• Hot spots


  Areas of the Earth's crust that are hotter than normal, where a plume of hot magma from the mantle moves towards the surface
• Types of volcanoes


  • Steep-sided composite volcanoes
  • Shallow-sided shield volcanoes
• Early warning systems


  • Can detect small movements and give seconds or minutes of warning before a large earthquake or volcanic eruption
  • Allow people and systems to take safety precautions
• Monitoring volcanoes


  • Detect telltale signs before an eruption to allow evacuation
  • Track ash clouds and poisonous gases during an eruption
• Building design


  • Use materials and techniques to prevent buildings collapsing in earthquakes or being damaged by volcanic ash
  • Design pipelines to flex not break during earthquakes