geo

• The atmosphere operates as a global system which transfers heat around the Earth


  The amount of heat from the sun varies around the Earth. Heat is distributed by pressure differences and ocean currents and if it wasn't, the tropics would be even hotter and polar regions would be even colder.
• Ocean currents


  Cold, salty water sinks at the Poles. It then flows towards the equator and is warmed again creating a convection current.
• Pressure differences


  1. Land heats quickly in summer and cools quickly in winter, air is heated above, becomes lighter and rises, forms low pressure in the summer and high pressure in winter.

  2. Sea takes longer to heat and cool, so the air is dense and cool in the summer, forms high pressure in summer and low pressure in winter.
• Inter-Tropical Convergence Zone (ITCZ)

  Occurs near the Equator between the two Hadley Cells, where warm tropical air converges at the Equator. The Sun's radiation is most intense at the Equator causing warm tropical air to rise rapidly creating an area of low pressure that brings heavy rainfall. As the rising air moves away from Equator it loses its moisture and density, descending to form arid regions.
• Global circulation model


  • Hadley Cell
  • Ferrel Cell
  • Polar Cell
• Theories explaining past climate change

  • Eruption theory
  • Asteroid collision theory
  • Sunspot theory
  • Orbital change theory
• Evidence of past climate change

  • Ice cores
  • Tree rings
  • Historical sources
• Enhanced greenhouse effect


  Human activities (industry, transport, energy, farming) produce greenhouse gases (carbon dioxide, methane) that trap heat from the sun and warm the planet.
• High-income and middle-income countries emit more carbon dioxide than low-income countries.
• Global warming

  • Near 1°C rise in average temperature since the early 1900s
  • Sea levels have risen over 200mm (thermal expansion) in the same period
  • Arctic sea ice has halved in area since 1980
  • 90% of the world's valley glaciers are shrinking
• Impacts of climate change

  • More frequent floods and droughts
  • Stronger storms (tropical cyclones)
  • Changes to farming (unreliable rainfall)
  • Climate refugees from people living in low-lying areas
• Predicting future climate change is difficult because we don't know how populations and economies may grow, fossil fuel consumption versus renewable energy and people's lifestyle choices.
• Tropical cyclone


  A rotating system of clouds and storms that forms over tropical waters (26.5°C) with winds which can exceed 118 km/h, known as a hurricane (Atlantic Ocean), typhoon (Pacific Ocean) and cyclone (Indian Ocean) and is measured on different scales, depending on their origin.
• Tropical cyclone formation

  1. Warm ocean (exceeding 26.5°C) creates a warm body of air to develop

  2. Strong winds draw the warm air up rapidly from the ocean surface

  3. Strong Coriolis force created by Earth's rotation (so not formed on or close to Equator where the force is too weak)
• Tropical cyclone hazards


  • Strong winds
  • Storm surges
  • Intense rainfall
  • Landslides
• Bangladesh's vulnerability to cyclones

  • Much of its population is rural living on low-lying flood-prone farmland
  • It is a poor country, and most its people are poor
• Bangladesh's attempts to protect the population from tropical cyclones

  1. Forecasting (forecast issued through tv and radio)

  2. Satellite technology (to track cyclones)

  3. Warning systems

  4. Evacuation strategies (cyclone shelters)

  5. Surge defences (embankments)
• Bangladesh has reduced the number of deaths, however warning systems are expensive and poverty meant that some people doesn't receive any warnings.
• Impacts of Cyclone Aila in Bangladesh

  • 190 people killed
  • 750,000 people made homeless
  • Crops destroyed
  • Farm animals killed
  • Sickness spread from contaminated water
• Impacts of Hurricane Katrina in the USA

  • 1,833 people died
  • Costed the economy US$108 billion
  • 80% of New Orleans flooded due to levee collapse
  • Many of the poor and elderly were left behind
  • 80% of the city was evacuated and some residents sheltered in the Super Dome stadium
• Earth's layered structure


  • Lithosphere (continental crust and oceanic crust)
  • Mantle (asthenosphere and lower mantle)
  • Core (outer liquid, inner solid)
• Earth's heating and convection currents


  • Radioactive decay in the core and mantle creates geothermal energy and convection currents that move tectonic plates
  • Rising heat creates plumes which bring magma to the surface
• Plate boundaries


  • Conservative (plates slide past each other)
  • Divergent (plates move apart, magma rises)
  • Convergent (plates push together, oceanic plate subducted)
• Earthquake magnitude

  Measured on the Richter Scale, which is logarithmic - a 6.0 quake is 10 times more powerful than 5.0
• Earthquake epicentre


  Directly above the focus, on the Earth's surface
• Impacts of earthquakes in different locations

  • Port-au-Prince (Haiti) - 300,000 people may have died, 1 million made homeless, cholera outbreak killed 8,000 people
  • Sendai (Japan) - 20,000 people killed, US$235 billion damage, 350,000 made homeless, nuclear meltdown
  • Nepal - 10,000 people killed
• Nepal's earthquake preparation


  Lightweight thatch roofing, simple steel foundations, cross-braced wood frame
• Development indicators

  • Economic (GDP per capita)
  • Social (literacy rate)
  • Political (corruption)
• Human Development Index (HDI)


  Uses an average of four indicators: life expectancy, literacy, average length of schooling, GDP per capita
• Relationship between economic development and other indicators

  As a country's wealth increases, most development indicators improve
• Demographic indicators

  Birth rate, gender equality, fertility rate
• Malawi's high fertility rate

  Due to poverty and fewer girls attending secondary school, meaning they marry earlier and have several children
• 1980 Brandt Report

  Divided the world into HICs (high-income countries) and LICs (low-income countries)
• There is a 'development gap' between the world's richest and poorest countries but there are also large variations within countries.
• Emerging country groups

  • MICs (middle-income countries)
  • NICs (newly industrialised countries)
  • RICs (recently industrialised countries)
• Rostow's stages of development


  1. Traditional society

  2. Pre-conditions for take-off

  3. Take-off

  4. Drive to maturity

  5. Age of high mass consumption
• Frank's dependency theory


  Development is about a core and periphery, where core regions exploit and underdevelop peripheral regions
• Country groups

  • High-income countries (HICs)
  • Middle-income countries (MICs)
  • Newly industrialised countries (NICs)
  • Recently industrialised countries (RICs)
  • Low-income countries (LICs)
• Development gap


  The gap between the world's richest and poorest countries, but there are also large variations within countries
• The development of manufactured goods is seen as the key to development