Which process leads to metamorphism in the rock cycle?

• A. Weathering
• B. Erosion
• C. Deposition
• D. Metamorphism

Answer: (D)

Metamorphism is the transformation of existing rocks into new minerals and textures under higher temperature and pressure (and often with interacting fluids). In the rock cycle, this happens when rock is buried deeper in the crust, squeezed by tectonic forces, or heated by nearby magma. These conditions cause minerals to recrystallize and re-align, producing metamorphic rocks such as slate, schist, and gneiss from shale or granite, or marble from limestone. This is a solid-state process, meaning the rock largely doesn’t melt; when melting is involved, that’s an igneous process, not metamorphism. Weathering, erosion, and deposition, by contrast, break down rock, transport it, and lay down sediments—steps that lead to sedimentary rocks rather than metamorphic ones.