The Law of Superposition helps scientists determine what?

• A. The chemical composition of minerals.
• B. The rate of erosion in a landscape.
• C. The relative age of rock layers.
• D. The sequence of fossilized organisms.

Answer: (C)

The main idea is that in undisturbed sedimentary rock layers, the oldest rocks sit at the bottom and each higher layer is younger than the one beneath it. This lets scientists compare layers and determine their relative ages—which layers are older and which are younger—without knowing their exact dates. Fossils found in deeper layers are generally older than those in upper layers, helping scientists trace the sequence of life over time. Remember, if the rock record has been disturbed by folding, faulting, erosion, or intrusions, the simple bottom-to-top rule needs to be considered alongside other clues.