Concept
Physiographic regions are a means of defining Earth's landforms into distinct regions, based upon the classic three-tiered approach by Nevin M. Fenneman in 1916, that separates landforms into physiographic divisions, physiographic provinces, and physiographic sections. Originally used in North America, the model became the basis for similar classifications of other continents, and was still considered valid . During the early 1900s, the study of regional-scale geomorphology was termed "physiography". Physiography later was considered to be a portmanteau of "physical" and "geography", and therefore synonymous with physical geography, and the concept became embroiled in controversy surrounding the appropriate concerns of that discipline. Some geomorphologists held to a geological basis for physiography and emphasized a concept of physiographic regions while a conflicting trend among geographers was to equate physiography with "pure morphology," separated from its geological heritage. In the period following World War II, the emergence of process, climatic, and quantitative studies led to a preference by many Earth scientists for the term "geomorphology" in order to suggest an analytical approach to landscapes rather than a descriptive one. In current usage, physiography still lends itself to confusion as to which meaning is meant, the more specialized "geomorphological" definition or the more encompassing "physical geography" definition. For the purposes of physiographic mapping, landforms are classified according to both their geologic structures and histories. Distinctions based on geologic age also correspond to physiographic distinctions where the forms are so recent as to be in their first erosion cycle, as is generally the case with sheets of glacial drift. Generally, forms which result from similar histories are characterized by certain similar features, and differences in history result in corresponding differences of form, usually resulting in distinctive features which are obvious to the casual observer, but this is not always the case.