In a stack of undisturbed rock layers, the upper layers are younger than the lower layers. this is also stated as the law of

The answer is: Law of superposition

Explanation:

In geochronology, the law of superposition is a fundamental principle given by the Danish scientist Nicolas Steno.

According to this law, in an undisturbed stratigraphic sequence, the youngest strata is always found on the top of the sequence, and the layers present below get progressively older as we go from the top to the bottom of the sequence. Thus, the oldest strata is found at the bottom of the stratigraphic sequence.

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