Question

A geologist finds four layers of sedimentary rock. She determines that no geologic events have shifted the layers. She labels the layers A, B, C, and D from the top to the bottom.

Which statement about these layers is accurate?

A is older than B.
B is older than C.
C is younger than A.
B is younger than D.

Answer 1

In sedimentary rock layers that have not been disturbed, the principle of superposition applies. This principle states that in undisturbed layers of rock, the older layers are at the bottom and the younger layers are at the top.

Given the layers labeled from top to bottom as A, B, C, and D:

- A is the youngest layer (topmost).
- B is younger than C (as it is higher up).
- C is younger than D (as it is also higher up than D).

Therefore, the accurate statements based on the order of the layers are:

1. A is younger than B.
2. B is younger than C.
3. C is younger than D.

Now, to evaluate the statements provided:

1. **A is older than B.** (Incorrect)
2. **B is older than C.** (Incorrect)
3. **C is younger than A.** (Correct)
4. **B is younger than D.** (Correct)

Based on this analysis, **the accurate statements are: "C is younger than A" and "B is younger than D."**

Among the given options, if only one accurate statement must be chosen, “B is younger than D” can be highlighted as it relates directly to the younger relationship.