Comments by "Alan Friesen" (@alanfriesen9837) on "PBS Eons" channel.

  1. What he's suggesting is that there used to be very little molecular oxygen in the atmosphere - that it was almost all tied up in carbon dioxide. When plant life took off it separated the CO2 into carbon-based plant fiber (later compressed into coal) and free oxygen. If we burn all the coal (along with oil and all living and remaining plant matter) the chemical reaction will pair up all the free oxygen in the atmosphere with those stored carbon atoms until the atmosphere returns to the state it was in prior to beginning of plant life which was far less oxygenated than any atmosphere we've seen since.
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  2. Because that geological rock layer is loaded with carbon I suspect.
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