An architectural term, pediment refers to a low gable, typically triangular with a horizontal cornice, surmounting a colonnade or otherwise signaling a significant division in a façade. In geology, the angularity of architectural pediments has been taken up to refer to a gently sloping rock platform at the foot of an abrupt rise or face. Pediments are sometimes triangular in shape. They often extend over a considerable area, and typically they cut across geologic formations. Such phenomena are found in all climatic zones, but are most visible in arid and semi-arid regions. The pediment’s surface has been eroded over a long period, and is mantled with a discontinuous veneer of alluvium fallen from above and in a state of transport across the pediment’s grade.

John Keeble