Question

read the text. then answer the question. a valley was covered by a glacier. the glacier deposited boulders, mud, and sand along its edges. over thousands of years, the glacier melted, and a lake formed in the valley. mud was deposited at the bottom of the lake, on top of the older sediment. which rock sequence is more likely to form from the sediment layers described above?

Explanation:

The problem is about sedimentary rock formation. Conglomerate is formed from large sediments like boulders, sand, etc. (as deposited by the glacier). Shale is formed from fine - grained sediments like mud. Since the glacier first deposited boulders, sand (which form conglomerate) and then mud (which forms shale when lithified), the sequence should have conglomerate (older, from glacier - deposited sediments) at the bottom and shale (younger, from lake - bottom mud deposition) on top. Limestone is usually formed from calcium - rich sediments (not mentioned in the text as part of the initial deposits).

Answer:

The rock sequence with conglomerate (older) at the bottom and shale (younger) on top (the second option in the image).