Via Highly Allochthonous comes this fascinating account of how the air we breathe became breathable. Being a science geek, I can’t help being fascinated by little details like the following:
In today’s oxidising atmosphere, when minerals like pyrite (an iron sulphide) and uraninite (uranium oxide) and siderite (iron carbonate) are exposed by erosion, they are quickly broken down. When you look at very old sedimentary sequences in Australia, South Africa and Canada, however, you sometimes find rounded clasts of pyrite and uraninite that have clearly been eroded and transported some distance by rivers without being altered. This can only happen in low-oxygen conditions (less than 1/1000th of the present atmospheric concentration of O2).
Of course, as an ex-creationist, I also can’t help remembering that, according to traditional creationism, those strata were laid down by the Flood, and contain the bones and stones of the things that existed prior to the sixth chapter of Genesis. Which means that there was virtually no breathable oxygen in the Garden of Eden. Nor would a Flood have done much good.–after all, if you’ve learned to get along without oxygen during the good weather, you’re not going to drown no matter how much it rains.