The Earth's sea and atmosphere

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The early atmosphere

The Earth's first atmosphere

  • The Earth's early atmosphere was formed by gases produced from volcanoes.
  •  It contained large amounts of carbon dioxide and water vapour, hardly any oxygen and mall amounts of other gases.
  • The Earth was very hot to start with, and there were no oceans. As the earth cooled down the water vapour in the atmosphere condensed to form liquid water, which became the oceans.

Adding oxygen and removing carbon dioxide

  • Adding oxygen:
    • Forms of life evolve in the ocean and photosynthesis begins.
    • Oxygen builds up in the oceans then in the atmosphere.
  • Removing carbon dioxide:
    • Carbon dioxide disolved in the oceans which marine organisms uses to make calcium carbonate for shells. 
    • Shells of dead marine organisms fall to sea bed and become part of the sediment. Sediment squash and become sedimenary rocks.
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A changing atmosphere

Atmosphere today:

  • Nitrogen- 78%
  • Oxygen 21%
  • Argon- 0.9%
  • Carbon dioxide- 0.04%
  • Other gases- traces.

Changes in the atmosphere

It can be changed by:

  • Burning fossil fuels- releases carbon dioxide and sulphur dioxide into atmosphere.
  • Farming- cattle and rice fields release methane
  • Deforestation- adds carbon dioxide if trees are burnt and fewer trees to remove carbon dioxide.
  • Volcanoes- emit sulphur dioxide and carbon dioxide when they erupt.
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