Contact between rocks over long periods of time causes rocks to smooth.
Metamorphic rocks are rocks formed by the alteration of preexisting rocks deep within the earth.
Contact between objects formed deep within the earth causes them to smooth.
what between objects formed deep within the Earth causes them to smooth
1: Movement
2: loose soil
3: erosion
4: contact
5: soils
6: break off
7: friction
8: Bend