This was a nice long ride through Badlands National Park, which was spectacular, and then the rolling prairie of central South Dakota. The sedimentary rock formations of the Badlands were laid down in layers over about 50 million years (roughly 75-25 million years ago) when the land was under water. The dinosaurs were around at the beginning of this time (until 65 million years ago), so dinosaur fossils might be found in the lowest layers. The land has been eroding away, yielding the spectacular hills, over only the last 500,000 years. The exposed rock is surprisingly soft, and it will erode away more-or-less completely in another 500,000 years. (Oops, sorry, I just slipped into professor mode there for a second.) The photos below are all from the Badlands.