What is the principal that states that younger rocks lie above other rocks?

The principal that states that younger rocks lie above other rocks in the superposition principal.

Aregion is an area of land that has common features. these features can be natural, such as climate or landscape. they can also be artificial, such as language or religion. the xinjiang uyghur autonomous region, above, is an area of china inhabited by uyghurs, a muslim group with ethnic ties to turkish people.