A pediment is a very gently sloping (.5 -7 ) inclined bedrock surface.

Striated bedrock surfaces are found in the col on the south side of Citadel Bastion.

Plunge: Water descends vertically, losing contact with the bedrock surface.

Saprolites form in the lower zones of soil profiles and represent deep weathering of the bedrock surface.

The middle grid is the uppermost surface of an economically important aquifer, the Mahomet Sand, which fills a pre- and inter-glacial valley carved into the bedrock surface.

Much of the bedrock surface is of Pennsylvanian age, including "cyclothemes", regular sequences of limestone, shale and coal layers.

North of the Illinois River the bedrock surface is much older Ordovician sandstone.

The northern shores are waterlogged whilst the bedrock surfaces along the southern.

Newfound glacial features include an ice-sculptured bedrock surface, residual stagnant-ice-contact deposits, a recessional moraine, and exposed glaciolacustrine sediments.

The bedrock surface cracked up further still, also outside the main fault lines, exacerbated by erosion by water and ice.