At the bottom of a roadcut in the southwest is pre-Cambrian granite, overlaid by limestone. In geologic time, other sedimentary strata like sandstone and ocean bottom fossils begin to turn up - brachiopods, chrinoid stems. Then you begin to see cultural artifacts, in relative scale, just a fraction of an inch compared to the miles of depth of the geologic datum.
Prehistoric traces become visible, and then the successive cultural strata.
The roadcut is a poetic diagram of an investigative process for the making of architecture. Lessons learned in the American Southwest apply anywhere in the world.