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| 1 bil. yrs. ago, a plant called blue-green algae appeared on Earth,which used photosynthesis to put 02 into the air.Some 02 atoms went high into the air and split and formed with 02 to make Ozone(03). | |
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| The Ozone blocked harmful rays of the sun, making it so that life can go on land.Even though the air's content of O2 was 10% of the present content, the Ozone still made it so life can thrive on land. | |
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Temperature of the Atmosphere...
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| 600 mil yrs ago,the Earth's global temp was steady at 22 0 celcius.150 mil yrs later the earth enters an Ice Age, and another Ice Age hits 150 mil yrs later.The temp stays roughly warm from then on. | |
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