It is possible to date the rocks by comparing the amount of specific radioactive isotopes they contain. Which of the statement is correct in this respect?

Correct answer: B. Older sediment layers have less amount of these radioactive isotopes as that of the young ones.

  • A. Older sediment layers have equal amount of these radioactive isotopes as that of the young ones
  • B. Older sediment layers have less amount of these radioactive isotopes as that of the young ones.
  • C. Older sediment layers have greater amount of these radioactive isotopes as that of the young ones.
  • D. Older sediment layers did not have these radioactive isotopes

Explanation

Radioactive parent isotopes decay with time, so an older rock generally contains less of the original radioactive isotope than a younger rock formed from the same material. Students may choose option c by thinking that age allows radioactive material to accumulate, but decay reduces the parent isotope instead.

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