1. Heat: This is the most important factor. Heat causes the atoms within the minerals of the original rock to vibrate faster, breaking existing bonds and allowing new ones to form. This process, known as recrystallization, changes the size, shape, and arrangement of the minerals, resulting in a new metamorphic rock.
2. Pressure: Pressure from the weight of overlying rock or from tectonic forces can also cause changes in the minerals within a rock. The pressure can cause existing minerals to be squeezed into new shapes or can cause new minerals to form. This process, known as deformation, can create new textures and structures within the metamorphic rock.
These two processes often work together to create metamorphic rocks. The specific type of metamorphic rock that forms depends on the type of original rock, the intensity of heat and pressure, and the presence of fluids.
