The Earth's early atmosphere

The Earth formed about 4.5 billion years ago. Scientists believe that its early atmosphere was produced by volcanic activity.

Volcano
A volcano in Iceland

Composition of the early atmosphere

The early atmosphere probably contained:

  • a large amount of carbon dioxide
  • water vapour
  • small amounts of other gases

As the Earth began to cool, water vapour condensed formed the oceans. This process can be explained by the particle model.

Formation of the modern atmosphere

Over time:

  • the oxygen levels increased
  • the carbon dioxide levels decreased
Air is composed of 78% nitrogen, 21% oxygen and 1% other gases, including 0.9% argon and 0.04% carbon dioxide.The composition of the modern atmosphere