This video provides a demonstration of two main principles in the study of rock layers: superposition and association.

Using beans and plastic figurines, archaeologist John Shea illustrates how older sediments are typically found lower in a sequence of rock layers. He also illustrates how fossils found in the same layer represent organisms that existed at around the same geologic time.

This clip is from a 2011 Holiday Lecture Series, Stones, Bones, and Genes: The Origin of Modern Humans.