Evolution of the Atmosphere

  • Theories on the development of Earth’s atmosphere have developed over time as science has progressed.
  • The surface of the early Earth was molten for millions of years during which time there was no atmosphere surrounding the planet.
  • Eventually cooling began to take effect and allow for molten materials to slow and solidify forming land masses.
  • Volcanoes formed on the land masses and released gases from the Earth’s interior through violent eruptions.
  • Earth’s gravity prevented the gases from escaping into outer space and they formed the atmosphere.
  • Analysis of the gases conserved in the fossil record has allowed scientists to perform studies of the composition of Earth’s early atmosphere.
  • It is thought that the atmosphere at that moment in Earth’s history was similar to that of Venus or Mars today which consist mainly of CO2.
  • During a period of intense volcanic activity, large amounts of carbon dioxide and water vapour were released, as well as nitrogen, hydrogen, ammonia, methane and other gases.
  • The early atmosphere therefore contained mainly CO2 and water vapour.
  • There was little or no oxygen present.

Early-Earth-Volcanoes, IGCSE & GCSE Chemistry revision notes

Volcanoes spewed out water, carbon dioxide and other gases from the Earth’s interior

  • While the surface of the Earth was still very hot the large quantities of water vapour remained in the gaseous state.
  • When conditions cooled sufficiently, the water vapour later condensed and fell to the surface of the Earth, forming the oceans.
  • Carbon dioxide is a water soluble gas (it is the gas used in fizzy drinks) and dissolves readily.
  • When the water vapour condensed large amounts of CO2 dissolved in the oceans.
  • Carbonate substances were precipitated during this process which later formed sediments.

AQA GCSE Chemistry Notes

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.