Composition of Today
The gas composition has stayed constant for 200m years before there were big changes but since the earth is 4.6b years old there isn’t much evidence for the exact composition.
other gases eg
Development of Composition
- For the first 1b years there was intense volcanic activity that released gases that formed the atmosphere.
ammonia, methane and water vapour. - As the earth cooled and condensed it formed liquid oceans.
- Then some
dissolved in oceans to form a weak acid reacting with minerals to form precipitates forming sediments of carbon rock and shells of some organisms. - ~2.7b years ago the first photosynthetic algae formed taking in
and releasing over time more organisms evolved to photosynthesise further reducing levels.