Metamorphic rock formation from sedimentary rocks is caused by heat and pressure. After millions of years in transformation, the heat and pressure of the Earth's crust changes the physical and chemical properties of rock creating new textures to the rock. Metamorphic rocks are separated into two categories by their texture, foliated rocks and non-foliated rocks. The foliation or _______________that occurs in metamorphic rock is because of the immense __________________ found deep within the Earth's interior.