Which principle tells you how rock layers are laid

Principle of superposition

Explanation:

The principle of superposition states that in an  undisturbed sequential layering of sedimentary or volcanic rocks the oldest rocks reside at the bottom and young continuously upward.

This principle highlight the fact that in region of rock deposition, older rocks are first laid before younger ones so far the region is devoid of earth natural activities like unconformity, tilting and faulting that can alter the sequential layering.

Naturally,  in a sedimentary terrain older sediments will first be deposited  before the younger sediment are laid.

This principle also apply to volcanic rocks as older lava are first laid before the younger ones.  

The picture above illustrate the principle of superposition . Notice as the rocks young upward as indicated.

because there are alot of mountains