Evolution of the atmosphere

• Phase 1 - volcanos give out gas

  • first billion years the surface of earth was covered with volcanoes that erupted lots of gas- how our early atmosphere formed
  • early atmosphere mostly CO2 with virtually no oxygen
  • volcanic activity also released nitrogen which built up as well as water vapour and methane and ammonia
• Phase 2- oceans, algae and green plants absorbed CO2

  • when the water vapour in atmosphere condensed it formed oceans
  • lots of CO2 was removed from early atmosphere as it dissolved to form sediments on the sea bed
  • green plants evolved and absorbed some of the CO2 to carry out photosynthesis. later marine animals revolved. and shells And skeletons contained Carbonates from oceans
  • some of the carbon these organisms took for atmosphere became locked up in rocks forming fossils fuels
• Phase 3- green plants and algae produced oxygen

  • produced O2 by photosynthesis
  • green plants evolved
  • as oxygen levels built up in the atmosphere over time more complex life could revolve
  • today’s atmospher- 80% nitrogen, 20% oxygen and small amounts of other gases