SIM will truly usher in the age of Exo-Geology. Here is a link to an article that describes the variety of geological styles that Other Earths may exhibit.
So far, we have only been able to study 2 Earth-Sized terrestrial planets, i.e., Earth and Venus. The "New Earths" discovered by SIM will, over the long term, revolutionize Geology. We have seen on Venus a version of Plate Tectonics that resembles that on the Earth, but which is not identical. Intriguing, but we will probably need to examine 10 or 20 Earths to pin down, with some detail, exactly which geological factors have determined the appearance, and environment, of our home planet. The road to this revolution begins with SIM. Over the years, and decades, and centuries, SIM will initially be followed by space telescopes that will produce crude maps of these Other Earths, leading eventually to direct probes to those far-off worlds.
We will see a variety of "Earths" that will open up a new frontier. These worlds could be in geological stages that are equivalents of the Earth's long series of geological epochs. These include the Archean, when the Earth was devoid of life; several episodes of "Snowball Earth" conditions; the Cambrian, when multi-celled life first appeared; the Mesozoic age of Dinosaurs; recovery from Giant Impacts; the Miocene worlds of Mammals before humans; the present epoch of Human Dominance; possible post-industrial epochs.
We will be able to examine those alternative worlds by having the will to start the process of Exploration, and that process begins with SIM.