This builds up as layer after layer of sediments pile on top of each other. it is necessary for the process of compaction?

The process described is sedimentation, where sediments accumulate over time due to erosion and deposition. Compaction is essential in sedimentary rock formation, as the weight of overlying sediments compresses the lower layers, reducing pore spaces and cementing particles together. This compaction increases the density and strength of the sedimentary rock.