Question

FAN AND MEDAL!! What are two examples of heat or pressure that can form metamorphic rock?

Answer 1

You can chose either one from the following source:

Contact metamorphism occurs when magma intrudes or forces its way into existing rock. The heat of the magma bakes the surrounding rocks causing them to change. This is a local event. The changes due to contact metamorphism are relatively small and are said to be low-grade metamorphism. An example of contact metamorphism is the metamorphic rock marble. Marble is created from limestone that has been subjected to heat.

Regional metamorphism by contrast takes place over large areas and is high-grade metamorphism. Regional metamorphism is associated with mountain building like these rocks on the cliff face of the Black Canyon of The Gunnison. It is mostly a metamorphic rock called gneiss. See picture below. The pink rocks you see are pegmatites which are igneous rocks that have squeezed their way into cracks in the older gneiss.
Dynamic metamorphism is metamorphism that is produced in zones such as faults or thrusts that are under high amounts of pressure. The way that this form of metamorphism works is that rocks are scraped against each other causing them to be ground into a powder. Then this powder is reformed due to the pressure in the zone and the heat caused by friction of the two rock surfaces. Due to the given conditions, we can determine that this metamorphism is mainly dependent on pressure and requires relatively low temperatures.

The heat and pressure comes from inside the earth. From the upper mantle up to within a few kilometers of the surface of the earth there is a tremendous amount of heat and pressure. This heat and pressure increase with depth. It is estimated that the temperature increases about 20o to 30o C per kilometer of depth.
Plate Tectonics Adds Heat And Pressure
There is something else that adds to both the heat and pressure, and that is plate tectonics. When the plates of the earth collide, they squeeze the rocks at the borders with unbelievable force. This force increases the pressure in this and surrounding areas. Friction is also created by the plates grinding together. This friction generates enough heat to melt the rocks at the point of contact.

http://www.rocksandminerals4u.com/metamorphic_rocks.html