Which principles states, that in undisturbed rock layers, the oldest rocks are on the bottom and the youngest rocks are on top

The correct answer is principle of superimposition.

Explanation:

According to the superimposition principle, in the undisturbed rocks, the youngest rocks are situated on the top and the oldest rocks are found in the bottom. The phenomenon takes place due to withering. The rocks get withered because of the influence of air and water.  

The soil particles or the sediments get gathered at another site. The deposits of sediments get concentrated with time and result in the production of rocks. The mature rocks get surrounded by the layers of sediments with time passing by. These sediments get concentrated again to produce novel rocks. Through this procedure, the fresh young rocks get produced over the older ones.