Relating to or resembling the Earth or its shape or surface configuration: Mr. Smart asked his students to read about the geomorphic aspects and structure of the Earth and report on it the next day.

Theory was developed or formulated by the American geographer and geomorphologist, William Morris Davis (between 1884 and 1934) who modeled the formation of river-eroded landscapes.

This theory suggests that landscapes go through three stages of development (youth, maturity, and old age) and indicates that the rejuvenation of landscapes arises from tectonic uplift of the land.

In the "youthful stage", under the influence of tectonic uplifts, there appears a mountain relief, which is dissected through erosion (the washing out of rocks by rivers) into deep, narrow valleys and sharp-peaked ridges.

With the dissection by streams, the area would reach maturity and, ultimately, would be reduced to an old-age surface called a peneplain (gently undulating, almost featureless plain), with an elevation near sea level.

The model developed by Davis, though important in historical context, is currently considered only a first approximation.

Developments in the sciences of geology and geomorphology, especially the plate tectonics revolution of the 1960s and 1970s, have confirmed the preliminary nature of the model.

The physical and chemical interactions between the Earth's surface and the natural forces acting upon it to produce landforms: The geomorphic processes are determined by such natural environmental variables as geology, climate, vegetation and baselevel, to say nothing of human interference. The nature of the process and the rate at which it operates will be influenced by a change in any of these variables.