Which process transforms existing rocks into metamorphic rocks, requiring heat and pressure?

• A. Weathering and erosion cause metamorphism.
• B. Cooling of magma transforms igneous rocks into metamorphic.
• C. Heat and pressure transform existing rocks into metamorphic rocks.
• D. Biological activity turns rocks into metamorphic.

Answer: (C)

Metamorphism is the process by which an existing rock is altered by heat and pressure to become a metamorphic rock. These conditions cause minerals to rearrange and recrystallize while the rock stays solid, often creating new textures such as foliation. This is precisely what the question describes: a solid-state transformation driven by heat and pressure.

Weathering and erosion break rocks down at the surface or near it, rather than transforming them into metamorphic textures. Cooling of magma forms igneous rocks as minerals crystallize from a melt, not through solid-state alteration of an already existing rock. Biological activity can change rocks in some ways, but it doesn’t provide the high heat and pressure required for metamorphism.