Final answer:
The movement of rocks along fault A would depend on the type of fault, where a normal fault suggests the left side moved up and the right side moved down, and a reverse fault suggests the opposite.Option B is the correct answer.
Step-by-step explanation:
When determining how the rocks moved along fault A, it is important to understand the nature of the motion based on the structures visible in the cross section. To determine the direction of movement, we can apply knowledge of geological faults. A normal fault is characterized by the hanging wall moving downward relative to the footwall, while in a reverse fault, the hanging wall moves upward.
If layer marked as 'a' aligns with a known direction of a normal fault, then option A would be correct: The rocks on the left side moved up, and the rocks on the right side moved down. However, if layer 'a' represents a reverse fault, option B would be the correct choice: The rocks on the right side moved up, and the rocks on the left side moved down. Without the visual reference of the fault and layer 'a', it is not possible to definitively provide the correct option in the final answer.
Nonetheless, discerning the type of fault and movement can often be done by comparing the strata on either side of the fault. A matching but offset layer suggests one side has moved relative to the other, while the rock type, such as igneous, sedimentary, or metamorphic, can sometimes provide clues to the history of movement and deformation.