Evolution of the atmosphere

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Phase 1-Volcanoes gave out gases

  • The earth's surface was orginally molten
  • Its was so hot that any atmosphere boiled away
  • When things eventually cooled down a thin crust formed
  • However volcanoes continued to erupt
  • The volcanoes gave out lots of gases
  • The main ones are; carbon dioxide and water vapour
  • However there was also small amounts of other gases too
  • According to this theory, the early atmosphere was mainly Carbon dioxide
  • There was barely any oxygen
  • It was like the atmosphere of Mars and Venus today
  • The oceans were formed when the water vapour condensed
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Phase 2- green plants evolved and produced oxygen

  • A lot of the carbon dioxide dissolved into the ocean
  • Later, when the marine organisms evolved, they absorbed some of the carbon dioxide
  • When they died they were buried under layers of sediment and carbon dioxide
  • They became locked up in carbonate rocks
  • Green plants evolved over most of the earth
  • They were happy
  • The green plants removed the carbon dioxide and replaced it with oxygen
  • They did using photosynthesis
  • This caused the oxgen levels to gradually increase
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Phase 3- ozone layer allows evolution of complex a

  • The increase of oxgen killed some of the early organisms that couldnt take it
  • However it allowed other, more complex organisms, to evolve and grow healthily
  • The oxygen created the ozone layer
  • The ozone layer blocks harmful rays from the sun
  • It also allows more complex organisms to evolve
  • There isnt much carbon dioxide left now
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