Which rock type forms from existing rocks changed by heat and pressure?

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

Answer: (A)

Metamorphic rocks form when existing rocks are altered by heat and pressure deep in the Earth, causing minerals to recrystallize and grains to reorient without melting. The heat speeds chemical reactions, while pressure or differential stress changes the rock’s texture—often creating a layered or foliated look as minerals align. Because no melting occurs, the rock remains solid but transforms into a new mineral assemblage, like slate from shale or marble from limestone. In contrast, sedimentary rocks come from weathered and deposited material that becomes lithified, igneous rocks form from cooling molten rock, and fossils are remains of organisms rather than a rock type.