When marine geologists collects a core of undeformed ocean-floor sediment, they know that the youngest layer is on the top of the core and the oldest is at the bottom because of the principle of __.

principle of superposition

Explanation:

Principle of superposition -

According to the principle of superposition , the positioning of the layer are in a manner that , the youngest layer is near to the surface of the crust , where as the oldest layer is deep inside from the surface of the crust , is referred to as principle of superposition .

This method enables to determine the age of the layers according to their placement from the crust .

Hence , from the given information of the question ,

The correct answer is principle of superposition .