What are metamorphic rocks?

• A. Rocks formed by weathering into sediment.
• B. Rocks formed from the alteration of existing rocks due to heat, pressure, or chemically active fluids.
• C. Rocks formed by cooling of magma at surface.
• D. Rocks formed by precipitation from seawater.

Answer: (B)

Metamorphic rocks form when an existing rock is transformed by heat, pressure, or chemically active fluids, while the rock remains solid. This leads to new minerals and textures, often producing features like foliation or banding, as seen in slate, marble, and gneiss. The key idea is alteration of preexisting rocks through metamorphism rather than melting or precipitation.

The described option captures this process: rocks formed from the alteration of existing rocks due to heat, pressure, or chemically active fluids. Weathering and erosion produce sediments that lithify into sedimentary rocks, cooling of magma at the surface creates igneous rocks, and precipitation from seawater forms chemical sedimentary rocks—none of which are metamorphic.