What type of rock is formed from sediment compaction and cementation?

• A. Sedimentary rock
• B. Igneous rock
• C. Clastic rock
• D. Metamorphic rock

Answer: (A)

Sedimentary rocks are formed when loose sediments are lithified through compaction and cementation. As layers of sediment accumulate, burial increases pressure, squeezing out water and air (compaction). Minerals dissolved in water then precipitate and bind the grains together, cementing them into a solid rock. This combination of pressing sediments and cementing them is what turns loose material into rock, specifically a sedimentary rock. Igneous rocks come from cooling molten material, metamorphic rocks come from existing rocks altered by heat and pressure, and clastic is a type of sedimentary rock defined by its grain fragments—the formation process described here leads to sedimentary rock overall.