How Carbon Dioxide Decreased (AQA GCSE Chemistry Combined Science): Revision Notes
📚 Revision Notes
9.1.4 How Carbon Dioxide Decreased
infoNote
The reduction of carbon dioxide in Earth's atmosphere was a gradual process influenced by both geological and biological factors.
Formation of Oceans and Sediments:
- Condensation of Water Vapour:
- The formation of oceans as water vapour condensed played a significant role in reducing atmospheric carbon dioxide.
- Carbon dioxide dissolved in the newly formed oceans, leading to the formation of carbonate sediments like limestone , which removed CO₂ from the atmosphere.
- Continued Reduction by Photosynthesis:
- The advent of photosynthesising organisms further reduced atmospheric CO₂ levels.
- As plants and algae absorbed carbon dioxide for photosynthesis, the amount of CO₂ in the air continued to decline.
Modern Atmospheric Composition:
- Over the course of billions of years, these processes reduced carbon dioxide levels and increased oxygen levels, leading to the modern atmosphere we have today.
- By about 200 million years ago, the atmosphere had stabilised into its current composition, with 78% nitrogen, 21% oxygen, and trace amounts of other gases, including carbon dioxide.