Explain why we know the lahar is older than the sedimentary layers on top of it.

In geology, the principle of superposition states that in an undisturbed sequence of sedimentary rock layers, the oldest layers are at the bottom and the layers get progressively younger as you move to the top. This principle is a key concept in relative dating of geological strata.

So, if we find a lahar (which is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water) beneath sedimentary layers, we can infer that the lahar is older. This is because the sedimentary layers must have been deposited on top of the lahar after it had occurred.

Therefore, the lahar must have occurred first for the sedimentary layers to be deposited on top of it, making the lahar older than the sedimentary layers above it.