Question

What happens to the rock when a sedimentary rock becomes metamorphic?

Answer 1

The force and heat of sedimentary rock under thousands of feet of earth above, will fuse the sedimentary particles (mainly grains of sand and other minerals) together. During this time, the movement of the layers of earth can distort the newly forming metamorphic material. When (millions of) years later the Metamorphic rock is exposed near the surface, it may have an appearance of granite but the granularity will be almost microscopic and it often appears to be layered with some of the layering being bent or distorted from bending and compression at great depths.