How is granite turned into a metamorphic rock?
Granite is turned into the metamorphic rock gneiss by heat and pressure that is normally regional in nature, i.e., it will cover a broad expanse of geography due to the actions of tectonic plate movements, and in particular, plate collisions. The incredible pressures that are experienced in a granite that is being subjected to these forces will cause the minerals in the rock to align themselves perpendicularly to the direction of the force being applied, causing a narrow parallel banding in their appearance called foliation.
