Compared to the Earth’s early atmosphere, the modern atmosphere is oxygen-rich. It contains:
Name the most abundant gas in the modern atmosphere.
The Earth cooled after it formed. When it became cool enough, water vapour in the atmosphere condensed. It fell as rain, creating the oceans.
Describe two reasons why the amount of carbon dioxide in the atmosphere decreased over time.
Carbon dioxide dissolved in the oceans, and primitive plants used it for photosynthesis.