How has Earth's atmosphere changed?


4.6 billion years ago:

>Earth started to cool

>A thin crust formed - there were no oceans at this point

>Periods of extreme volcanic activity released gases (carbon dioxide, Nitrogen, and water vapour)

>oceans began to form when the water vapour condensed and fell as rain.

4 billion years ago:

>The earth began to stabalise

> There were traces of methane and ammonia

3.4 billion years ago:

>The first simple organisms began to form (very much similar to bacteria)

2.7 billion years ago:



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