The Evolution of the Atmosphere

• What is the topic of the study material?

  Chemistry of the atmosphere
• What does the study material discuss about the Earth's atmosphere?

  It evolved and changed over the years
• How long ago did the Earth's atmosphere begin to evolve?

  4.6 billion years ago
• Why is it hard to gather evidence about the early atmosphere?

  Because it was a long time ago
• What is Phase 1 of the atmosphere's evolution?

  • Volcanic gases released
  • Surface was covered in volcanoes
  • Released lots of gases
• What was the composition of the early atmosphere primarily made of?

  Mostly carbon dioxide
• How does the early atmosphere compare to Mars and Venus today?

  It was similar to their atmospheres
• What gases did volcanic activity release into the atmosphere?

  Nitrogen, water vapor, and methane
• What is Phase 2 of the atmosphere's evolution?

  • Oceans formed from condensed water vapor
  • Carbon dioxide was removed from the atmosphere
  • Carbon dioxide dissolved in oceans
• What did the condensation of water vapor form?

  The oceans
• What happened to carbon dioxide in the early atmosphere?

  It was removed by dissolving in oceans
• What processes led to the formation of sedimentary rocks?

  Reactions forming carbonates in oceans
• What is Phase 3 of the atmosphere's evolution?

  • Green plants and algae evolved
  • They absorbed carbon dioxide
  • They carried out photosynthesis
• What did green plants and algae absorb from the atmosphere?

  Carbon dioxide
• What process did green plants and algae perform?

  Photosynthesis
• What happened to marine animals as the atmosphere evolved?

  They evolved and developed shells
• What did the shells and skeletons of marine animals contain?

  Carbonates
• What happened to carbon in organisms after they died?

  • Became locked in rocks
  • Formed fossil fuels
  • Contributed to carbon levels in atmosphere
• What are fossil fuels made from?

  Decomposed organisms
• How do fossil fuels affect carbon dioxide levels in the atmosphere?

  They increase carbon dioxide levels
• What are the main sources of fossil fuels?

  • Decomposed plants and animals
  • Organic matter trapped in sediment
  • Geological processes over millions of years
• What do fossil fuels help reduce in the atmosphere?

  Carbon dioxide levels
• What are fossil fuels made from?

  • Coal
  • Crude oil
  • Natural gas
  • Formed from ancient organic matter
• What are fossil fuels called?

  Fossil fuels
• How are crude oil and natural gas formed?

  From deposits of plankton
• Where do fossil fuels form reservoirs?

  Under seabeds
• What is coal made from?

  Thick plant deposits
• What is limestone primarily made of?

  Calcium carbonate
• What are the primary sources of limestone?

  Shells and skeletons of marine organisms
• What is the process of photosynthesis in plants?

  1. Light absorption by chlorophyll
  2. Conversion of carbon dioxide and water into glucose and oxygen
  3. Chemical equation:

  • $6CO_2 +$$6H_2O \xrightarrow{light} C_6H_{12}O_6 +$$6O_2$
• How long ago did algae evolve?

  About 2.7 billion years ago
• What evolved after algae?

  Green plants
• How have oxygen levels changed over time?

  They have built up in the atmosphere
• What is the current atmospheric composition?

  80% nitrogen, 20% oxygen
• What gases make up less than 1% of the atmosphere?

  Other noble gases
• What does the study of ice layers reveal?

  Changes in atmospheric composition
• What is the significance of Antarctic ice cores?

  They provide historical atmospheric data
• What happens to air trapped in ice layers over time?

  It shows changes in atmospheric conditions
• How does the depth of ice affect air composition?

  Deeper ice contains older air
• How are sedimentary rocks formed?

  • Formed from particles and organic materials
  • Compacted and cemented over time
  • Examples include limestone and coal