What are metamorphic rocks primarily formed through?

Metamorphic rocks are primarily formed through heat and pressure. This process occurs when existing rocks, either igneous or sedimentary, are subjected to intense temperatures and pressures within the Earth's crust. These conditions can cause the minerals within the rock to recrystallize, resulting in new mineral compositions and structures that differ from the original rock.

The process of metamorphism can occur over a range of temperatures and pressures, and it can produce various metamorphic rock types, such as schist, gneiss, and slate. The transformation typically occurs without the rock melting, which would instead lead to igneous rock formation.

Cementation refers to the process by which sedimentary rocks are formed and is characterized by the binding of sediment particles together. Weathering involves the breakdown of rock at the Earth's surface, while cooling and solidification pertain to the formation of igneous rocks from molten material. Therefore, while these processes are critical in the rock cycle, they do not contribute to the formation of metamorphic rocks, which is exclusively the result of heat and pressure.