Principle which describes the layering of rocks. It states the oldest rock is on the bottom and the youngest is on the top.

In a sequence of sedimentary rock layers, each layer must be younger than the one below, for a layer of sediment cannot accumulate unless there is already a substrate on which it can collect.

The scientific law stating that in any unaltered sequence of rock strata, each stratum is younger than the one beneath it and older than the one above it, so that the youngest stratum will be at the top of the sequence and the oldest at the bottom.

the displacement of any point due to the superposition of wave systems is equal to the sum of the displacements of the individual waves at that point; "the principle of superposition is the basis of the wave theory of light"

Displacement due to two or more forces, is equal to vector sum of forces.

at any instant, the resulting wave is the algebraic sum of all the component waves