Wikipedia
Erosion surface
In geology and geomorphology an erosion surface is a surface of rock or regolith that was formed by erosion and not by construction (e.g. lava flows, sediment deposition) nor fault displacement. Erosional surfaces within the stratigraphic record are known as unconformities, but not all unconformities are buried erosion surfaces. Erosion surfaces can be either small or large. Particularly large and flat erosion surfaces receive the names of peneplain, paleoplain, planation surface or pediplain.