Question

the text below describes how an areas environment changed over time. read the text. then answer the question.
fine sediment was deposited on the floor of a deep ocean.
over thousands of years, the sea level fell. the area became a shallow part of the ocean. a coral reef started growing on top of the older sediment. over time, a layer of sediment was deposited on the floor of the reef. this sediment was made mostly of the shells of marine organisms.
the sediment deposited in these environments was pressed together to form rock. which statement best describes this rock?
the rock has two layers: an older layer made of shale and a younger layer made of limestone.
the rock has two layers: a layer of shale and a layer of limestone that are about the same age.
the rock has two layers: an older layer made of limestone and a younger layer made of shale.

Explanation:

Step1: Analyze the formation of the first - layer sediment

Fine sediment deposited in the deep ocean. Shale is a sedimentary rock formed from fine - grained sediment (such as clay, silt). So the older layer (from the deep - ocean sediment) is likely shale.

Step2: Analyze the formation of the second - layer sediment

The second - layer sediment was deposited on the floor of the coral reef and was made mostly of the shells of marine organisms. Limestone is a sedimentary rock that can be formed from the accumulation of shell fragments (biochemical sediment). Also, in sedimentary rock layers, the lower layer is generally older.

Answer:

The rock has two layers: an older layer made of shale and a younger layer made of limestone.