How is metamorphic rock primarily formed?

Metamorphic rock is primarily formed through the processes of heat, pressure, and chemical reactions. This transformation occurs when pre-existing rocks—either igneous, sedimentary, or even other metamorphic rocks—are subjected to significant changes in temperature and pressure within the Earth's crust. The intense conditions can alter the mineral composition and structure of the rock without it melting, leading to the formation of metamorphic rock.

During this process, original minerals may recrystallize, new minerals may form, and the texture of the rock can change, resulting in types of metamorphic rocks such as schist or gneiss. Chemical reactions can also occur that further contribute to the changes in mineral composition. This distinguishes the formation of metamorphic rocks from other rock types and highlights the importance of heat and pressure in their development.