The morning I'll sit in on a session on the Franciscan rocks of California, a tribute to USGS scientist emeritus Clark Blake. These are always fun because the speakers praise their colleague and mentor, and the person being honored takes part with his or her own talk. I'm sentimental about science. I'll also see a few talks about Archean greenstone belts, a stubborn mystery in the earliest history of Earth that is often treated as if these rocks were only slightly different from today, but in fact all bets are off when we contemplate Earth 3 and 4 billion years ago. It really was a deeply different, or at least deeply indeterminate planet back then.