Question

Which statement about how geologists study the ages of rock layers is true?

The law of superposition means that older rocks are on top.
Geologists can find the exact age of a rock by looking at its relative position.
The principle of original horizontality provides the basis for the law of superposition.
Relative age can be determined by using the concept of unconformity.

Answer 1

The true statement is: "Relative age can be determined by using the concept of unconformity."

Brief clarifications:
- The law of superposition means older rocks are on the bottom, not on top.
- Relative position gives relative (older/younger) ages, not exact (absolute) ages.
- Original horizontality and superposition are both basic principles of stratigraphy; original horizontality does not itself state the ordering of ages (that's the law of superposition).