How does sedimentary rock become metamorphic rock?
Sedimentary rock becomes metamorphic rock through the addition of heat and/or pressure. Contact metamorphic rocks are those primarily transformed by close proximity to an intrusion of magma, where a recrystallization or elemental transfer can take place. Sedimentary rocks like shale can metamorphose into slate mainly through pressure and heat derived from plate collision, where the alignment of minerals is changed resulting in a foliated texture.