1. Heat: Intense heat, often generated by the Earth's internal heat or from magma intrusions, causes the minerals within the rock to recrystallize and change their structure. This process is called thermal metamorphism.
2. Pressure: Extreme pressure, often caused by tectonic plate movements, can also cause changes in the rock's mineral composition and structure. This is known as dynamothermal metamorphism.
It's important to note that both heat and pressure usually act together to form metamorphic rocks. The specific combination of heat and pressure, as well as the original rock type, determines the resulting metamorphic rock.
