what takes longer to form, a sedimentary rock or a metamorphic rock

Answer 1

Metamorphic rocks form when land folds, thus any sudden change in landscape from a folding line to something similar presses the minerals quickly to form rock, while sedimentary is a slower process of striation/stratification begun in a river bed or other running body of water. Therefore it would appear that metamorphic rock takes much less time to form. Shale and slate are two examples of how similar minerals form rocks by different processes.