Which process forms sedimentary rocks by compaction and cementation of sediments?

• A. Melting rocks to form lava
• B. Lithification (compaction and cementation) of sediments to form sedimentary rocks
• C. Erosion of rocks by wind
• D. Metamorphism of rocks due to heat and pressure

Answer: (B)

Sedimentary rocks form when loose sediments are buried and hardened through lithification. In lithification, the weight of overlying layers compresses the grains (compaction), squeezing out water and air and squeezing the sediment into a tighter mass. Minerals dissolved in groundwater then precipitate between the grains and cement them together (cementation), turning loose fragments into solid rock. This creates rocks like sandstone, shale, and limestone. The other processes produce different rock types: melting creates igneous rocks, erosion is the breakdown and transport of rocks, and metamorphism changes rocks under heat and pressure.