Which rock type forms when pre-existing rock is transformed by heat, pressure, or active fluids?

• A. Igneous
• B. Sedimentary
• C. Metamorphic
• D. Eolian

Answer: (C)

Metamorphic rocks form when an existing rock is transformed by heat, pressure, or chemically active fluids deep in the Earth. This transformation changes the mineral grains and structure without melting the rock, so you get new minerals and textures that reflect the conditions of temperature and pressure. Heat and pressure cause minerals to recrystallize and realign, often producing foliation or banding, while fluids like water or carbon dioxide help drive chemical reactions that forge new minerals. Examples include slate from shale, marble from limestone, and quartzite from sandstone. In contrast, igneous rocks come from magma cooling and solidifying, sedimentary rocks from weathering, erosion, deposition, and lithification, and eolian effects describe wind-driven processes that shape sediments rather than transform existing rocks.