Final answer:
Metamorphic rocks are formed from the transformation of pre-existing rocks under extreme heat and pressure, deep within the Earth, often associated with mountain building or the heat from magma.
Step-by-step explanation:
Metamorphic Rocks
Metamorphic rocks are formed from pre-existing rocks that have been transformed by extreme heat and pressure. The process of formation is called metamorphism, which involves physical and chemical alterations deep within the Earth's crust, often occurring during mountain building or from the heat of nearby magma bodies. For example, sedimentary rock like sandstone can be converted into quartzite, and limestone can transform into marble. The specific characteristics of metamorphic rocks, such as the presence of foliation or certain mineral assemblages, tell us about the conditions of temperature and pressure they were subjected to during their formation.