Thirty miles south of my Provo home, near the top of a wide canyon, a glimpse of dark rock peeks out between garbled conglomerates of sandstone and limestone. This rock, the color of shadow, the color of age and memory and history, is two and a half billion years old. This rock, the bit that has sustained itself, whether by circumstance or pure stubbornness, lies in this canyon alongside rocks that are 700 million years old. A mere couple of billion years missing between them. The great Unconformity, in other words — erasure. This quiet, dark rock is part of what is known as the basement rocks, or craton. These are the rocks, the literal foundation of our entire world. The most ancient material on record.