(1) A shape into which the Earth's surface has been sculptured by natural forces. (2) One of the many features which, taken together, make up the surface of the Earth. The term includes all such broad features as plains, plateaus, and mountains, as well as such minor features as hills, valleys, slopes, canyons, arroyos, alluvial fans, terraces and glacial deposits. Most of these features result from erosion and resistance to erosion. The term also includes all features resulting from sedimentation and from movements within the crust. A landform can be portrayed by various means and various inferences can be made as to its probable origin, cause or history. Whether it is called a topographic landform or a physiographic landform depends upon how it is being used. However, the term landform is used extensively in place of and with the meaning of the more restrictive term physiographic form. It is also written as two words, land form, which is preferred by some writers. Note that the definition applies not merely to features on land but also to features under water, e.g., submarine canyons.