The Earth’s Atmosphere – Summary
notes
4.7 billion years ago, the Earth was formed.
Volcanic activity released CO2 and heat, making up most of the
atmosphere. Other greenhouse gases such as water vapour, CH4, N2
and NH3 ammonia are present in smaller amounts
Earth cools, water vapour condensed to form oceans. Carbonate
precipitates were formed when CO2 dissolved and reacted with
seawater. These precipitates got deposited as sediment. CO2 levels
are reduced. → sediments + animal skeletons + high pressure = coal +
limestone, which also reduced CO2 levels.
bacteria, algae and simple organisms began to populate oceans about
2.7 billion years ago. They photosynthesised, producing oxygen, and
removing CO2. once a certain amount was present, other complex
organisms began to populate Earth. Early organisms died out,
unable to cope with the increased oxygen concentration.
As animals and plants died, their remains stayed heated in the
Earth’s crust, forming fossil fuels. The carbon dioxide in their bodies (in
the blood of animals and the biomass of plants due to respiration) was
thus locked up.
methane reacted with oxygen to form water vapour and CO2, reducing its
amount
ammonia reacted with oxygen to form water vapour and nitrogen,
reducing its amount
nitrogen is very unreactive so has built up over time
now, the atmosphere is about 80% nitrogen and 20% oxygen, with traces
of other gases
greenhouse gases maintain the earth’s temperature so life can be
sustained.
the sun emits short and long wavelength radiation. the earth
absorbs a portion of this, but also reflects longer wavelength
radiation back to space. Some of this is absorbed by greenhouse
gases in the atmopshere, which then re-radiate the wavelengths in
all directions, including back to earth.
greenhous natural causes human causes
e gas
carbon respiration, large volcanic burning fossil fuels →
dioxide eruptions, forest fires, decay of electricity, driving
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