The age of rock is calculated on the basis of

Options

A. Type of fossils-present
B. Number of strata present
C. Amount of thorium present
D. Amount of lead present

Answer

To determine the age of a rock, scientists primarily use radiometric dating techniques, which involve measuring the amounts of certain radioactive elements and their stable decay products within the rock. Here’s a step-by-step breakdown of how this process works:

### Step-by-Step Solution:

1. **Understanding Radioactive Decay**:
- Rocks often contain radioactive isotopes, such as uranium-238, which decay over time into stable isotopes, like lead-206. This process occurs at a predictable rate known as the half-life.

2. **Identifying the Isotope**:
- In the case of dating rocks, uranium is commonly used because it is abundant in many types of rocks and has a well-known half-life.

3. **Measuring Isotope Ratios**:
- Scientists measure the ratio of the parent isotope (uranium) to the daughter isotope (lead) in the rock sample.

4. **Calculating Age**:
- By knowing the half-life of uranium, scientists can calculate how long it has taken for a certain amount of uranium to decay into lead. This calculation gives an estimate of the rock's age.

5. **Conclusion**:
- Therefore, the age of a rock is calculated based on the amount of lead present in relation to the amount of uranium, as lead is the end product of uranium decay.

### Final Answer:
The age of rock is calculated on the basis of the **amount of lead present**.

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