GCSE Combined Science (AQA)

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The Early Atmosphere

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Chemistry of the atmosphere The composition and evolution of the Earth's atmosphere

The Early Atmosphere

5:16 Changes in Earth's Atmosphere Over Time
Spec 4.9.1.2
Previous The Atmosphere Today Next The Early Atmosphere: Oxygen
  • The Earth formed approximately 4.6 billion years ago.
  • Initially, the Earth had no oceans and the land was red hot.
  • Scientists have limited evidence about the early atmosphere's gases and formation.
  • The current atmosphere is mostly oxygen and nitrogen.
  • Theories suggest intense volcanic activity in the first billion years released gases forming the early atmosphere.
  • Volcanic eruptions released magma with dissolved chemicals, forming volcanic gases.
  • Early atmosphere likely similar to Mars and Venus, mostly carbon dioxide with little or no oxygen.
  • Carbon dioxide made up nearly three-quarters of the early atmosphere, with nitrogen and water making up less than a quarter.
  • Volcanoes also produced nitrogen, which built up over time due to its unreactive nature.
  • Methane and ammonia were likely present in small proportions.
  • Volcanoes released water vapor, which condensed to form oceans.
  • Cooling of the Earth allowed water vapor to condense into liquid, forming oceans.
  • Oceans dissolved carbon dioxide, reducing its atmospheric levels.
  • Soluble carbonate compounds formed from dissolved CO2, precipitating as sediments.
  • Precipitation of carbonates led to sedimentary rock formation, trapping CO2 and reducing atmospheric levels.
  • This process is a significant reason for the current lower levels of CO2 in the atmosphere.

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