The two-stage concept of landform and landscape development involving etching: origin, development and implications of an idea

Two-stage development of landforms has been appreciated for more than two centuries with respect to minor features, and major forms and landscapes have been viewed in similar terms for almost a hundred years. Early workers understood the significance of fractures as passages for water and, hence, as avenues of weathering, the tendency for weathering to produce rounded forms, the progression of weathering from the surface downwards, weathering contrasts between wet and dry sites, contrasted erosive susceptibility of weathered and unweathered rock, and reinforcement effects. Forms of deep and shallow derivation can be differentiated. tever name it is known—etch, double planation, subcutaneous, or two-stage—the concept is one of the most fruitful developed in the last century, for it bears not only on the origin of a wide range of landforms, but also on the crucial role of water and weathering, the age of landforms and landscapes, palaeogeographic reconstructions, climatic geomorphology and theories of landscape development.