Back in December, I had the chance to walk through New York's Museum of Natural History with Ebonmuse (of Daylight Atheism). He pointed out an exquisite stone from the Proterozoic Eon. You could plainly see broad streaks of pure iron running from side to side. Such streaks could never form today, due to our oxygen-rich environment. That observation was the beginning of a mind-expanding yet poetic story. I learned a bit of that story back in December. Now, Ebonmuse tells a much more expansive and dramatic version. Here's an excerpt, but I'd highly recommend a visit to Daylight Atheism for the full dose:

Looking at this stone, you get some idea of the dizzying vistas of geological time, as well as the turmoil that life has endured to reach the present day. Each of those colorful red and silver layers represents what was, in its own era, a disaster beyond imagining, one that reset life to its starting point. Each of those layers, as well, is a silent testament to life's tenacity in the face of overwhelming odds. Of course, the cycles of growth and destruction did not last forever. Eventually, evolution found a way, as evolution nearly always does, and oxygen was tamed to become a power source in an entirely new metabolic cycle. The oxygen-breathers arose, the remaining anaerobes retreated to the deep crevices of rocks and the sea, and life found a new equilibrium, with the balance of the atmosphere permanently changed. All the oxygen we breathe today is biologically produced, a tangible proof of life's power to reshape its own world.