Law of Superposition

A relative‑dating rule stating that in an undisturbed sequence of stratified sedimentary rocks, each layer is younger than the one beneath it and older than the one above it.

In a sequence of undisturbed, stratified deposits, each depositional layer (stratum) is younger than the one it overlies and older than the one that overlies it; the law provides a relative chronological ordering of strata but not absolute ages.