What statement best describes the Law of Superposition?

• A. In undisturbed layers of sedimentary rock, the lowest layers contain the older rocks.
• B. Each sedimentary layer of rock represents 1000 years of Earth's age, much like the rings of a tree.
• C. In undisturbed layers of sedimentary rock, the upper rock layers are older than the lower rock layers.
• D. Rocks that form near volcanoes are older than surrounding rock.

Answer: (A)

The Law of Superposition means that in undisturbed sedimentary rock layers, the oldest material sits at the bottom and younger layers pile on top. The statement that the lowest layers contain the older rocks matches this idea directly: as sediments settle and accumulate, new layers form on top of older ones, so the bottom is oldest. The other ideas either assume a fixed time for each layer, claim the upper layers are older, or bring in unrelated factors like volcanic activity, none of which describe how relative ages are determined in a stacked sequence of sedimentary rock.