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8 Cards in this Set

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what gases did the early atmosphere contain

large amount of carbon dioxide


little amount of oxygen, ammonia, nitrogen, water vapour

what gases exist in today's atmosphere

78% nitrogen


21% oxygen


0.9% argon


0.04% carbon dioxide

why can't we be certain about where our atmosphere came from

the atmosphere of Titan is 98% nitrogen (released from volcanoes) scientists think earth may have been like this. there are also volcanoes on Mars and Venus but mainly CO2. this led scientists to believe earths atmosphere was CO2

how can we be almost certain that Earth was like Mars and venus

space probes show that Titans interior was icy and Mars and Venus' was rocky

why did oxygen incresse

the growth of primitive plants used CO2 and released oxygen by photosynthesis

why did CO2 decrease

1) absorbed by plants for photosynthesis


2) dissolved in oceans


3) locked up in sedimentary rocks like limestone and in fossil fuels

how does human activity increase CO2

increased energy consumption is leading to a rise in the use of fossil fuels which increases CO2



when land is cleared for farms and timber there are fewer trees to remove CO2 from the atmosphere by photosynthesis

how did oceans form

as the earth became older it cooled down. the water vapour in the hot atmosphere cooled down and condensed to form liquid water