Earth's Early Atmosphere (AQA GCSE Chemistry: Combined Science)

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Evolution of the atmosphere

  • Theories on the development of Earth’s atmosphere have altered and developed over time as instrumental analysis has improved
    • It is difficult to gather evidence about the early atmosphere because it happened 4.6 billion years ago
  • The surface of the early Earth was molten for millions of years with no atmosphere 
  • As cooling slowly occurred, the molten surface began to slowly solidify into land masses
  • Volcanoes formed on the land masses
  • One theory of how the early atmosphere formed suggests that the volcanoes released gases from the Earth’s interior through violent eruptions
  • These eruptions released large amounts of carbon dioxide and water vapour, as well as nitrogen, hydrogen, and other gases which may have included small proportions of ammonia and methane

How volcanoes affected the atmosphere

diagram to show early earth volcanoes producing gases

 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
  • These processes reduced the amount of carbon dioxide in the atmosphere

Examiner Tip

For this topic you should be able to describe this theory of how the atmosphere and oceans came about. You may be given information on alternative theories which you could be asked to evaluate.

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Stewart

Author: Stewart

Expertise: Chemistry Lead

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Exam Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.