<P> Metamorphic rocks arise from the transformation of existing rock types , in a process called metamorphism , which means `` change in form '' . The original rock ( protolith ) is subjected to heat ( temperatures greater than 150 to 200 ° C ) and pressure ( 100 megapascals ( 1,000 bar ) or more ) , causing profound physical or chemical change . The protolith may be a sedimentary , igneous , or existing metamorphic rock . </P>
<P> Metamorphic rocks arise from the transformation of existing rock types , in a process called metamorphism , which means `` change in form '' . The original rock ( protolith ) is subjected to heat ( temperatures greater than 150 to 200 ° C ) and pressure ( 100 megapascals ( 1,000 bar ) or more ) , causing profound physical or chemical change . The protolith may be a sedimentary , igneous , or existing metamorphic rock . </P>
an existing rock that changes during metamorphism to create a metamorphic rock is called
an existing rock that changes during metamorphism to create a metamorphic rock is called
protolith
protolith