C.13 Earths Atmosphere
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What are the main gases and their percents in our atmosphere?
Nitrogen - 78% Oxygen - 21% Argon -0.9% CO2 - 0.04%
Why is it hard to know about the early atmosphere?
Because it was so long ago that most evidence is destroyed
What was the early atmosphere like? What planets was it similar to?
CO2 - 95% Water Vapour - 4% Other gases - Trace Mars and Venus
Theory for formation of the Atmosphere
• 4.6 billion years ago - Temperature was around 400C so all the water was gas - Atmosphere like Venus and Mars • Temperature cooled down - Water became a liquid - Fell as liquid and formed oceans • 3.4 billion years ago - Simple microorganisms evolved - Broke down chemicals as energy • 2.7 Billions years ago - Algae evolved - Photosynthesised CO2 levels fall, O2 levels rise • Photosynthesis makes atmosphere 02 rich - Animals can evolve
What did volcanoes release
• CO2 • H20 • N2 (has remained in atmosphere as it is unreactive)
How did oceans effect CO2 levels
• Carbon is soluble in water • Forms insoluble metal carbonates • Sedimentary Rocks form which lock up the Carbon
Organism which produced oxygen
Algae
Word equation for Photosythesis
Carbon Dioxide + Water –> Oxygen + Glucose
Symbol Equation for photosynthesis
6CO2 + 6H2O —> 6O2 + C6H12O6 (everything has 6 expcet glucose and glucose is CHO 6,12,6)
How do algae reduce CO2 levels
Photosynthesis
When did algae first photosynthesise
2.7 billion years ago
Why were evolution of plant and algae important for other species to evolve
As they produced O2 which allowed other species to evolve
How did plants and animals decrease CO2 level
• Photosynthesis • Used to make shells and skeletons • When animals die it got locked up in coal and crude oil
Changes in atmosphere
• Water vapour condensed • O2 produced • CO2 used up • Methane reacted with O2 to make CO2 + H20 • Ammonia reacted with O2 to make nitrate + H2O
How crude oil and gas formed
• Ancient biomass compressed and buried under sedimentary rock • Heat and pressure turn into liquid crude oil + gas
How is coal formed
• Dead plants buried under layers of rock • Heat and pressure forms coal
How is limestone formed
• When carbon reacted with the ocean it formed metal carbonates • Included Calcium Carbonate • Used for shells and skeletons • Compressed by heat and pressur
3 main greenhouse gases
• Carbon Dioxide • Methane • Water Vapour
Why are greenhouse gases necessary
They trap heat in and keep the earth warm
Greenhouse effect
• Short wavelength radiation pass from sun throgh the greenhouse gases • The earth absorbs some of the short wavelength radiation - remits it as thermal long wavelength • This long wavelength radiation is absorbed by greenhouse gases • The Greenhouse gases re-radiate the thermal radiation in all directions including back to earth warming up the surface of the planet
What human activities have increased CO2 levels
• Burning fossil fuels • Deforestations which results in less trees to photosynthesise • Land fill
What human activities have increased methane levels
• Rice fields • Grazing cattle • Land fill
What is peer reviewed evidence and what has it led scientist to believe
• Peer reviewed evidence is evidence that is looked and agreed up by many scientist • Evidence such as a rapid increase in CO2 level at the same time as industriel revolution happened
Why is it hard to model/predict climate change
As there are so many factors that effect it