The ground under an old site is a book written one page at a time. A flood drops silt, a house burns to ash, roofs fall and dust blows in — each event lays a layer, oldest at the bottom, newest on top. That is the law of superposition, and it lets you build a timeline without knowing a single date.
The catch is the word undisturbed. People dig — graves, wells, post-holes, looters' pits — and every hole punches a younger thing down into older layers. A pit can leave a Roman coin resting below a Bronze-Age hearth. A flood can scour a century clean away, so the record simply skips it. The skill is reading the disturbances as carefully as the layers.
Because the top is youngest, you excavate in reverse — newest layer first, working down into deeper time. And you can only read the book once: to see a lower page you must remove the one above it, and that page is gone forever. That is why a real dig is so painfully slow. It is controlled destruction, and the information was never in the dirt — it was in the order.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.