evolution of the atmosphere

• phase 1- volcanoes gave out gases

  • In the first billion years of Earth's history, the surface was covered with Volcanoes that erupted and let out lots of gas, which is how the early atmosphere was formed
  • It was probably mostly carbon dioxide, with virtually no oxygen.
  • volcanic activity released nitrogen, which built up in the atmosphere over time, as well as water vapour and small amounts of Methane and ammonia
• phase 2 - oceans, algae and green plants absorbed carbon dioxide

  • when the water vapour in the atmosphere condensed, it formed the oceans
  • Lots of CO2 was removed from the early atmosphere as it dissolved in the oceans. this dissolved CO2 the formed carbonate precipitates that formed sediments on the seabed
  • Green plants and algae evolved and absorbed some of the CO2 so that they could carry out photosynthesis. When marine animals evolved their Shells contained carbonates from the oceans
• phase 3 - green plants and algae produced oxygen

  • As oxygen levels built up in the atmosphere, more complex life could evolve
  • Eventually, about 200 million years ago, the atmosphere reached the composition of 80% nitrogen, 20% oxygen and small amounts of other gases
• Greenhouse effect


  The process by which greenhouse gases in the atmosphere absorb and trap long wavelength radiation emitted from the Earth's surface, causing the temperature of the atmosphere to increase
• Main greenhouse gases


  • Water vapor
  • Carbon dioxide
  • Methane
• Greenhouse effect


  1. Short wavelength radiation from the Sun passes through the atmosphere

  2. Short wavelength radiation is absorbed by the Earth's surface

  3. Earth's surface emits long wavelength radiation

  4. Greenhouse gases in the atmosphere absorb and trap the long wavelength radiation

  5. Trapping of long wavelength radiation causes the temperature of the atmosphere to increase
• The greenhouse effect keeps the temperature on Earth warm enough to support life
• Without the greenhouse effect, the Earth would be too cold for most living organisms to survive