Question

In absolute dating, age of the rock/fossil is determined by
a. Depth of rock
b. Exposure of rock
c. Decay of a radioisotope
d. Rate of surface erosion of rock

Answer 1

Absolute dating methods provide the exact or chronological age of the rock or fossil. The method commonly used in the radiometric dating method is based on some natural activity of certain elements such as carbon and potassium. This method is very reliable to determine the age of rock or fossils.

Complete answer:
Absolute dating is a process of determining the exact age of a rock or fossil. The primary method of absolute dating includes the radioactive decay of those elements that are trapped in a rock or fossil.

This technique is based on the constant and known decay rate of the radioactive isotopes into their radiogenic daughter isotopes. Some of the rocks and minerals contain radioactive isotopes. The amount of parent and daughter isotopes in a rock can be measured and used to find out their age.

If the half-life of an isotope is known then the amount of parent and daughter isotopes can find out and also the amount of time that has been passed since the start of the radiometric clock can also be calculated.

Some of the elements that are used for radioactive dating are Carbon-14, Potassium- 40, Uranium-235, Rubidium-87, etc.

Hence, the correct answer is option (C).

Note: The half-life of an isotope can be defined as the time required for half of the nuclei in a sample of a specific isotope to undergo radioactive decay.
Also, the decay rate of many radioactive isotopes measured does not change over time thus every radioactive isotope has been decaying at the same rate since its formation, constituting a radiometric clock.