The Evolution of the Atmosphere

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  • Chemistry of the Atmosphere - The Evolution of the Atmosphere
    • Phase 1 - VOLCANOES gave out GASES
      • 1. First BILLION YEARS - surface covered in VOLCANOES that erupted and released gases. We think this is how the EARLY ATMOSPHERE was formed.
        • 2. Probably mostly CARBON DIOXIDE, VIRTUALLY NO OXYGEN.
          • 3. Also released NITROGEN, built up over time as well as WATER VAPOUR and small amounts of METHANE and AMMONIA.
    • Phase 2 - OCEANS, ALGAE and GREEN PLANTS ABSORBED CARBON DIOXIDE
      • 1. When the water vapour CONDENSED it formed the OCEANS.
        • 2. Carbon dioxide DISSOLVED in oceans. Went through reactions and formed CARBONATE PRECIPITATES that formed SEDIMENTS on the SEABED
          • 3. GREEN PLANTS and ALGAE evolved and absorbed some of the carbon dioxide so they could carry out PHOTOSYNTHESIS. Marine ANIMALS evolved. Their SHELLS and SKELETONS contained CARBONATES from the oceans.
            • 4. ROCKS and FOSSIL FUELS locked carbon after organisms that absorbed it died.
              • When plants and animals DIE they fall and get BURIED by LAYERS OF SEDIMENT. Millions of years pass and they get COMPRESSED and form SEDIMENTARY ROCKS, OIL and GAS. This helps keep carbon dioxide levels REDUCED as carbon is trapped
                • COAL is a sedimentary rock made from thick PLANT DEPOSITS.
                • LIMESTONE is also a s rock. Mostly made of CALCIUM CARBONATE from the SHELLS and SKELETONS of marine ainimals
              • CRUDE OIL and NATURAL GAS are formed from deposits of PLANKTON.
    • Phase 3 - Green plants and algae PRODUCED OXYGEN
      • 1. As well as absorbing CD they produce oxygen by PHOTOSYNTHESIS - when plants use light to convert CD and water into SUGARS.
        • 2. Algae evolved FIRST. About 2.7 BILLION years ago. Then over the next BILLION, green plants also evolved.
          • 3. As oxygen rised, more COMPLEX LIFE could evolve.
            • 4. About 200 MILLION YEARS AGO the atmosphere reached a composition similar to what it is TODAY. About 80% nitrogen, 20% oxygen and small amounts of other gases that makes up less than 1% like CD, noble gases and WV.

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