1. Pre-existing rock: Metamorphic rocks are formed when existing rocks, called protoliths, are transformed by heat and pressure. These protoliths can be igneous, sedimentary, or even other metamorphic rocks.
2. Heat and pressure: The heat and pressure cause the minerals in the protolith to recrystallize and change their arrangement. This can lead to changes in the rock's texture, mineral composition, and overall structure.
So, to summarize, a pre-existing rock subjected to heat and pressure will become a metamorphic rock.
