law of superposition: Meaning and Definition of

law' of superposi'tion

Pronunciation: [key]
  1. a basic law of geochronology, stating that in any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom, each layer being younger than the one beneath it and older than the one above it.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.