Question

which statement explains why carbon - 14 dating cannot be used to date ancient rocks? carbon - 14 decays at a varying rate. carbon - 14 decays quickly leaving the amount too small to measure. carbon - 14 can be used only to date the remains of organisms. carbon - 14 has a half - life that is much longer than potassium.

Explanation:

Carbon - 14 dating relies on the uptake of carbon - 14 by living organisms. Rocks are not living organisms and do not take in carbon - 14 in the same way as biological organisms. Carbon - 14 has a half - life of about 5730 years. For very old rocks (hundreds of millions or billions of years old), the amount of carbon - 14 would be extremely small (after many half - lives, the amount \(N = N_0\times(\frac{1}{2})^n\) where \(n\) is the number of half - lives). But the key reason is its biological association.

Answer:

Carbon - 14 can be used only to date the remains of organisms.