The Earth's Early Atmosphere - AQA GCSE Combined Science

Overview

• The early atmosphere was composed mainly of carbon dioxide and water vapor.
• Water vapor condensed to form oceans.
• Photosynthesis contributed to the decrease in carbon dioxide and increase in oxygen.

Formation of the Earth's Atmosphere

• Earth formed approximately 4.6 billion years ago.
• The composition of the early atmosphere is not certain due to a lack of evidence.
• Theories about the atmospheric development have evolved with new discoveries.

Volcanic Activity Hypothesis

• Intense volcanic activity likely released gases into the atmosphere.
• Similarity with current atmospheres of Mars and Venus:
  • High carbon dioxide levels
  • Little to no oxygen
  • Small amounts of ammonia and methane
• Volcanic activity also released water vapor, which condensed to form oceans.
• Nitrogen was released and accumulated because of its unreactive nature.

Modern Atmosphere Composition

• Stable for approximately 200 million years.
• Main gases in the current atmosphere:
  • Nitrogen (most abundant)
  • Oxygen
  • Carbon Dioxide
• The composition is shown in a pie chart of modern atmospheric gases.

Key Takeaway

• Nitrogen is the most abundant gas in the current atmosphere.

Additional Resources

• Explore further topics on atmospheric pollution and chemistry at various educational levels on BBC Bitesize.