What happens when radioactive elements are not present in dating fossils?

• A. They use carbon dating anyway.
• B. They guess randomly.
• C. They measure the fossil's weight to determine its age.
• D. Scientists turn to stratigraphy to estimate the age of a fossil based on the age of the strata in which it is found.

Answer: (D)

When you can’t use radioactive dating, you estimate a fossil’s age from the rock around it. This relies on stratigraphy—the study of rock layers and their sequence. By examining the order of layers, using marker beds, dating volcanic ash layers within the sequence, or correlating layers with other well-dated locations, scientists assign an age range to the fossil based on the age of the strata it sits in. This approach works because layers build up over time, so younger rocks lie above older ones, and certain fossil assemblages or marker events help tie a local sequence to a broader timescale. Carbon dating or other radiometric methods can’t be used here if the necessary radioactive elements aren’t present, and guessing or measuring an object's weight doesn’t yield a reliable age.