Fig. 59 The Shournagh River and the Inniscarra gorge in Cork show how rivers have cut across a ridge of sandstone. They have superimposed themselves on an older landscape.
Cycle of erosion and peneplains
The major theories of landscape development outlined a sequence of events whereby a newly uplifted landmass would be worn down by weathering and the agents of erosion (rivers, ice, sea, wind) to produce a flat plain (peneplain) with residual low hills. This landscape would then be uplifted again by earth movements and the cycle would start once more. Isostacy, eustacy and river rejuvenation all contribute to the formation of peneplains.