C13 - History of Earth's atmoshpere

4.6 billion yrs ago

volanic activity

-volcanoes released co2, water vapour, nitrogen

watre vapour condensed as Earths temp cools -fell as rain -collecting in hollows of the crust -icy comets rained down on Earth = melted

mainly co2 -h2o n2 methane and ammonia no o2

3.4 billion yrs ago

used breakdown of chemicals as energy

-algae used enegry from sun to photosynthesis -producing o2 as a waste product

growth of algae/bacteria in oceans thrived -released o2 as a waste product -plants populated Earth

as o2 levels rose -couldn’t tolerate rich o2 atmosphere as they weren’t used to it

co2 in photosynthesis is converted to glucosed = plant structure -as animals consume plants converted into body/bones -skeletons of marine life built up at bottom ocean -covered w layers of sediment -extreme pressure = sedimentary rock

contains mainly calcium carbonate -sedimentary rocks

-remains of ancient organisms -crushed by large scale movements of earth -heated within earth’s crust over long time

-sedimentary rock -formed by plants dying in swamps -in absence of o2 and being compressed

-formation from plankton in muds/ seadbeds -covered by sediment/ compressed -trapped beneath layers of rocks

-by dissolving in oceans -reacted w metal oxide + precipitate fell to seabeds

-reacted w o2 from photosynthesis

-unreactive gas so it stayed

78% = nitrogen 21% = o2 argon = 0.9% co2 = 0.04%

absorb energy radiated from earth’s surface

-earth is heated by the sun -30% is reflected back to space -earths emits longer wavelength infrared to cool -ghg absorb infrared -trapped radiation = heats molecules + raises temp

short - wavenlength (UV) to pass through

more infrared absorbed

combustion of fossil fuels - electricity