C1 TOPIC 1 – THE EARTH’S SEA AND ATMOSPHERE
THE EVOLUTION OF THE ATMOSPHERE.
Phase 1 – Volcanoes gave out gases.
1) The Earth’s surface was originally molten, it was very hot. 2) Eventually the surface cooled down and a bit crust formed. Volcanoes kept erupting. 3) Volcanoes gave out gases: CO2, water vapour and small amounts of other gases. (water and oceans formed) 4) The early atmosphere: mostly CO2, with no oxygen.
5) The oceans formed when the water vapour condensed.
Phase 2- Green plants evolved and produced oxygen.
1) A lot of CO2 dissolved into the oceans.
2) Marine organisms developed which took some of this CO2. When they died the organisms were buried under layer of sediments and the CO2 became “locked up” in carbonate rocks. 3) Green plants evolve over most of the Earth.
4) Green plants removed CO2 from the air and produced O2 by photosynthesis. (oxygen level increased) Phase 3 – Ozone layer allows evolution of complex animals. 1) The built-up of oxygen in the atmosphere allowed more complex organisms to evolve and flourish. 2) The oxygen also created the ozone layer (O3) which blocked harmful rays from the sun and enable more complex organisms to evolve. 3) There is very little C02 left now.
The atmosphere is still changing.
Human activity is changing the atmosphere.
1) Burning fossils fuels increases CO2 – as the world has become more industrialised, more fossils have been burnt. 2) Deforestation also increases the level of CO2. Less trees will remove CO2 from the air. 3) Livestock farming releases methane CH4, into the atmosphere when animals wind. Volcanic activity is changing the atmosphere.
1) Sulfur dioxide is released into the atmosphere when volcanoes erupt. 2) Carbon dioxide is also released into the atmosphere by volcanoes eruptions. Sources of information of the atmosphere are limited.
1) We have learnt about the past atmosphere from Antartic ice...
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