Which type of rock forms when particles from other rocks or the remains of plants and animals are pressed and cemented together?

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

Answer: (A)

Rocks formed when particles from other rocks or the remains of plants and animals are pressed and cemented together are sedimentary rocks. This happens through lithification: loose sediment is deposited in layers, the weight of overlying material compacts the grains, and minerals dissolved in water precipitate between the grains to cement them into a solid rock. The cemented fragments can be bits of other rocks or fossils from plants and animals, which is why sedimentary rocks often contain layered structures and sometimes preserved remains.

Igneous rocks come from molten rock that cools and solidifies, not from pressing together existing pieces. Metamorphic rocks form when existing rocks are transformed by heat and pressure, changing minerals and texture rather than simply binding particles with cement. Erosion is the process that wears away rock, not a type of rock.