the atmosphere

• Gases in the atmosphere today

  • Nitrogen
  • Oxygen
  • Carbon dioxide
  • Water vapor
  • Noble gases such as argon
• Gases in the atmosphere have stayed pretty constant for around 200 million years
• During the first billion years, there was intense volcanic activity releasing gases that formed the atmosphere
• One of the gases released during intense volcanic activity was water vapor
• Early Earth's atmosphere consisted mainly of carbon dioxide with little or no oxygen
• Early Earth's atmosphere was similar to the atmospheres of Mars and Venus today
• Volcanoes also released nitrogen which gradually built up in the atmosphere
• Volcanoes also released small amounts of methane and ammonia
• Early atmosphere consisted mainly of carbon dioxide with small but increasing amounts of nitrogen
• Early atmosphere contained large amounts of carbon dioxide but today's atmosphere contains only a small amount
• Early atmosphere contained very little oxygen, whereas today's atmosphere contains 21% oxygen
• Formation of oceans

  Water vapor from volcanoes condensed to form the oceans
• Formation of sediments

  Carbon dioxide dissolved in the oceans to form a weak acid, reacting with minerals to form precipitates and sediments of carbonate rock on the seabed
• Formation of limestone


  Some carbon dioxide in the sea was used to make corals and shells of organisms, forming sedimentary rock limestone
• Production of oxygen

  Photosynthetic algae first evolved in the oceans around 2.7 billion years ago, producing oxygen which entered the atmosphere
• Increase in oxygen


  Plants evolved, increasing the amount of oxygen in the atmosphere
• Reduction of carbon dioxide

  Photosynthesis takes in carbon dioxide, trapping carbon in fossil fuels and causing the level of carbon dioxide in the atmosphere to fall
• Photosynthesis also takes in carbon dioxide
• Photosynthesis equation is shown
• Fossil fuels are formed trapping carbon dioxide and reducing its level in the atmosphere
• Fossil fuels


  • Coal
  • Oil
  • Gas
• Fossil fuels are formed over millions of years
• Fossil fuels are non-renewable
• Formation of coal

  Formed from the remains of ferns and trees that do not decompose in marshy wetlands due to lack of oxygen or acidic conditions. Plant remains are covered with sediment, compressed, and high temperature and pressure create coal
• Formation of oil

  Crude oil is formed from plankton settling in mud on the seabed, compressed by sediment and heat and pressure convert them into crude oil
• Formation of natural gas

  Natural gas, mainly methane, is formed from plankton in a similar way to oil, often found near deposits of oil
• Old fossil fuels contain trapped carbon that was part of the carbon dioxide taken in by photosynthesis
• Burning fossil fuels


  Effects on the planet
• Greenhouse effect

  1. Energy from the Sun travels to the earth as short wavelength radiation (e.g., ultraviolet and visible-light)

  2. Short wavelength radiation reflects back into space or passes easily through the atmosphere

  3. Short wavelength radiation is absorbed by the earth's surface and radiated as long wavelength radiation (e.g., infrared)

  4. Some long wavelength radiation interacts with greenhouse gas molecules in the atmosphere, causing the atmosphere's temperature to increase
• Main greenhouse gases

  • Water vapor
  • Carbon dioxide
  • Methane
• The atmosphere contains around 78% nitrogen, 21% oxygen, and 1% other gases including water vapor, carbon dioxide, and tiny amounts of methane
• Water vapor, carbon dioxide, and methane are all greenhouse gases
• Greenhouse gases trap long wavelength radiation in the atmosphere, causing the temperature to increase
• Greenhouse effect

  Keeps the temperature on earth warm enough to support life
• Human activities that increase greenhouse gases

  1. Burning fossil fuels (coal for electricity, petrol and diesel for cars, gas for heating homes)

  2. Deforestation (burning forests for land for grazing cattle)

  3. Agriculture (growing rice in flooded paddy fields, methane released by cattle)
• Potential effects of global climate change

  • Increased melting of polar ice sheets and glaciers
  • Rising sea levels
  • More flooding of low-lying areas
  • More severe weather (e.g., storms)
  • Changes in animal distribution (e.g., insects)
  • Changes in distribution of insect-borne diseases (e.g., malaria)
• Levels of carbon dioxide and methane in the atmosphere are increasing due to human activity
• Increasing levels of carbon dioxide and methane in the atmosphere

  Lead to a rise in temperature and trapping more energy from the Sun
• The Earth is facing climate change
• Possible effects of climate change

  • Increased melting of polar ice sheets and glaciers
  • Rising sea levels
  • More flooding of low-lying areas
  • More severe weather (e.g., storms)
  • Changes in animal distribution (e.g., insects)
  • Changes in distribution of insect-borne diseases (e.g., malaria)