HI :)
Answer:
First sedimentary rocks were formed when sediments shifted down under water. Next more sediment covered the earlier sediment. Also the amount of water on top of the sediment might have increased. Consequently its weight put even more pressure on the sediment. Additionally over millions of years, the sediment became rock. Finally the was thrust up so that we can see its layer to day in places like Grand Canyon.
SORRY IF I'M WRONG!!!
HOPE THIS HELPS :) !!!