Where do metamorphic rocks form?

• A. In surface rainforests.
• B. Deep within the Earth's crust where heat and pressure are sufficient to cause metamorphism.
• C. In outer space.
• D. In volcanic ash deposits.

Answer: (B)

Metamorphism happens when existing rocks are transformed by high heat and pressure deep inside the Earth's crust, enough to change their minerals and texture without melting. These conditions arise most often where tectonic plates interact or where magma intrudes, driving mineral changes and possible foliation as rocks recrystallize. For example, limestone can become marble, and shale can become slate, then phyllite, schist, or gneiss, as temperature and pressure rise.

The other scenarios don’t provide the sustained high temperatures and pressures needed for metamorphism: surface rainforest conditions emphasize weathering rather than mineral changes from burial or compression; outer space lacks the Earth-like interior conditions that drive metamorphism; volcanic ash deposits form at or near the surface and, at most, may lithify by diagenesis rather than undergo the deep-crust metamorphism that produces metamorphic rocks.