The principle of superposition is used to compare the ages of rocks, typically used by geologists.

In physics and systems theory, the superposition principle, also known as ... principle holds (which is often but not always; see nonlinear optics), ...

The principle of superposition states that a rock layer on top of another is younger than the one beneath it. Geologists use the principle of superposition to determine the relative ages of rock layers.

the relationship between relative age and the principle of superposition is look it up yourself!

superposition of waves is the vector sum of the individual displacements