What process forms sedimentary rock?

What process forms sedimentary rock?

• A. Compaction and cementation of sediments
• B. Metamorphism
• C. Crystallization of magma
• D. Weathering and erosion

Answer: (A)

Sedimentary rocks form when loose sediments are buried and pressed together and then cemented by minerals in groundwater. After rocks are weathered and broken into grains, those grains are transported and deposited in layers. As more layers accumulate, the weight of the overlying material squeezes the particles closer together (compaction) and minerals precipitate from water to glue grains in place (cementation). This combination—compactness and cementing—lithifies the sediments into solid rock, like sandstone, shale, or limestone.

The other processes point to different steps or outcomes. Metamorphism changes rocks under high heat and pressure into metamorphic rocks. Crystallization of magma forms igneous rocks when magma cools and solidifies. Weathering and erosion are the sources of the sediments themselves and do not by themselves turn loose material into rock.