In the book Super Volcanoes, I read about how complex the moon is geologically and how little of it we've examined and how poor our understanding of the geological history is. Apparently we can't yet explain how it was geologically active so recently. Imagine if the only rock samples we had from Earth were from a couple random spots on the surface, from wildly different time periods, and trying to develop together a theory of how its geology changed over time from that.