The Earth's Sea and Atmosphere
- The early atmoshpere was formed from volcanic activity and comprised mainly carbon dioxide and water vapour. Evidence for the early atmosphere is found in gases trapped in rocks and in the oxidation of iron in rocks.
- Early oceans formed as water vapour condensed. They absorbed carbon dioxide to make carbonate rock.
- Photosynthesis eventually caused decreased C02 and increased O2 in the atmosphere. The modern atmosphere is mostly nitrogen and oxygen with tiny amounts of carbon dioxide.