earths atmosphere

• give current composition of gases in earth atmosphere

  nitrogen - 80

  oxygen - 20

  other gases - carbon dioxide, water vapour and noble gases - small proportion
• give order of events forming earths atmosphere

  1. volcanic activity
  2. ocean formation
  3. organism evolution
• describe affect of volcanic activity

  released gases of early atmosphere - carbon dioxide and water vapour
• describe affect of ocean formation

  water vapour condensed to form oceans that dissolved carbon dioxide converting carbonates to sediment
• describe affect of organism evolution

  algae and green plants photosynthesised decreasing carbon dioxide and increasing oxygen