Which method would a scientist use to date a fossil by comparing its content to known species in other rock layers?

• A. Relative dating
• B. Radioactive dating
• C. Absolute dating
• D. Convergent boundary

Answer: (A)

Dating fossils by comparing the species present in a rock layer to species known from other layers is an example of relative dating. The idea is that sedimentary layers form in a time sequence and organisms appear and disappear in a recognizable order. When a fossil assemblage in one layer matches assemblages in well-dated layers elsewhere, you can place that layer in the same time interval and determine which layers are older or younger. This method doesn’t give an exact numerical age; it simply orders layers by age. In contrast, radioactive dating uses decay rates to calculate a specific age in years, and a convergent boundary is a tectonic concept, not a dating method. So, using fossil content to link layers across sites is relative dating.