The Early Atmosphere

The Early Atmosphere

1. The early atmosphere of the Earth was formed from gases that escaped from volcanoes.

2. The main gases in the early atmospheres were water vapour (H2O) and carbon dioxide (CO2) because these are gases still produced by modern volcanoes.

3. Rocks contain a record of the gases that were in the atmosphere at the time they formed.

4. Scientists analyse rocks that formed at different times to provide evidence for the way the atmosphere has changed.

5. The atmosphere of volcanic planets such as Mars provides evidence for the early atmosphere of Earth.

6. Oxygen is one of the most reactive gases in the atmosphere.

7. Oxidation reactions can be seen in rusting metals and the maintenance of fire.

8. The type of iron compounds found in rocks leaves a permanent record of the oxygen content of the atmosphere at the time the rocks were formed.

9. More recent rocks contain iron oxide, but in older rocks the iron is not oxidised. This provides evidence that oxygen levels in the atmosphere have increased.

10. Nitrogen has also increased and carbon dioxide has dramatically decreased.