How can one type or rock become many different types of metamorphic rock?

  When a certain type of rock, specifically, an igneous rock, is deeper into the ground, and it is under the influence of high temperatures and pressures, it will start to change its molecular structure over time. In addition to the high temperature and pressure, chemical influences are also very important, so the the rock will gradually turn into a metamorphic rock.

  Depending on the type of influences, and their intensity as well, one type of rock can evolve into multiple different types of metamorphic rocks.

heat from the core of the earth causes convection currents to occur in the mantle. these currents slowly move the crust around.