I’m three billion years before the present day, in the Mesoarchean. I’ve been having trouble, admittedly, staying in the mindset of the Mesoarchean. Maybe it’s the massive snowdrifts climbing up my windows and canyoning the streets.
But the other thing that’s tricky about this time in Earth’s history is that it is - you guessed it - a little unclear what’s happening. Most scientists agree that there are bacteria active by now, but there’s disagreement over what they’re doing. Are they respiring oxygen? When did oxygenic photosynthesis arise? Geobiologists look for clues in roundabout ways, studying banded iron formations, or the sorption of molybdenum onto manganese oxides. It’s still years (okay, half a billion years) before the “Great Oxidization Event” (see you in March!), but there’s a decent chance bacteria are making oxygen available to the marine world here in the Mesoarchean. But it hasn’t bloomed into the atmosphere yet.
The first supercontinent has formed, called Vaalbara. Part South Africa, part Western Australia, it’s greenstone and granite, pockmarked by craters, scattered with spherules. You take the last four letters of Kaapvaal, in South Africa, and the last four of Pilbara, in Australia. A pleasing way to make a continent.