AQA GCSE Chemistry

Revision Notes

9.1.2 Earth's Early Atmosphere

Evolution of the Atmosphere

  • Theories on the development of Earth’s atmosphere have developed over time as instrumental analysis has improved
  • 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 slowly 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 minerals in the earth’s crust enables scientists to deduce the gases present millions of years ago that helped form those minerals
  • 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

Exam Tip

For this topic you should be able to describe how the atmosphere and oceans came about.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.

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