The earths early atmosphere

• The early atmosphere was mainly carbon dioxide and water vapour
• Water vapour condensed to form the oceans
• Photosynthesis caused the amount of carbon dioxide to decrease and oxygen to increase
• Atmosphere


  The layers of gases that surround the Earth. The important gases are nitrogen, oxygen and carbon dioxide
• The Earth formed approximately 4.6 billion years ago
• Scientists cannot be certain about what gases made up the Earth's early atmosphere
• Early atmosphere theories


  • Came from intense volcanic activity, which released gases similar to Mars and Venus
  • Volcanic activity also released water vapour which condensed to form oceans
  • Nitrogen was probably also released by volcanoes and gradually built up in the atmosphere because it is unreactive
• For approximately 200 million years, the proportions of different gases in the atmosphere have been relatively stable
• Composition of the modern atmosphere

  • Nitrogen
  • Oxygen
  • Carbon dioxide
  • Other gases
• Nitrogen is the most abundant gas in the modern atmosphere