Geomorphic aspects of normal and accelerated erosion

The twin concepts “normal erosion” and “accelerated erosion” commonly considered to include all erosion past and present, are disarmingly simple, if interpreted literally, they suggest that accelerated erosion was unknown before the coming of man, and, conversely, that the changes brought about by man merely quickened the pace of certain normal processes. Both of these interpretations are misleading. Realizing that normal erosion was a flexible quantity varying widely with meteorological, tectonic, and other influences, Lowdermllk, in 1929, set up an idealized standard of natural erosion, aptly named the “geologic norm of erosion” [see 6 and 7 of “References” at end of paper]. Erosion was considered in the broadest possible sense and was made to include the mass‐movement processes, many of which are highly effective in the natural denudation of the lands.