Archaeological layers can act like pages.

Older material is often buried beneath later material, although farming and other disturbances can mix layers.

If a Spanish object is found in a layer associated with a Native structure that can be dated to the early sixteenth century, the relationship becomes meaningful.

Researchers can compare pottery styles and other artifacts.

They can use environmental evidence.

They can study patterns of burning or rebuilding.

Each piece contributes to a chronology.