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A landform is a geomorphological unit, and is largely defined by its surface form and location in the landscape. As part of the terrain, a landform is an element of topography. Landform elements also include land such as hills, mountains, plateaus, canyons, valleys, seascape and oceanic waterbody interface features such as bays, peninsulas, seas and so forth, including sub-aqueous terrain features such as mid-ocean ridges, volcanoes, and the great ocean basins.
Landforms are categorized by characteristic physical attributes such as elevation, slope, orientation, stratification, rock exposure, and soil type.
Gross physical features or landforms include intuitive elements such as berms, mounds, hills, ridges, cliffs, valleys, rivers, peninsulas and numerous other structural and size-scaled (i.e. ponds vs. lakes, hills vs. mountains) elements including various kinds of inland and oceanic waterbodies and sub-surface features.
Hierarchy of classes
Oceans and continents exemplify the highest-order landforms. Landform elements are parts of a high-order landforms that can be further identified and systematically given a cohesive definition such as hill-tops, shoulders, saddles, foreslopes and backslopes.
Some generic landform elements including: pits, peaks, channels, ridges, passes, pools and plains.
Terrain (or relief) is the third or vertical dimension of land surface. Topography is the study of terrain, although the word is often used as a synonym for relief itself. When relief is described underwater, the term bathymetry is used. In cartography, many different techniques are used to describe relief, including contour lines and TIN (Triangulated irregular network).
Elementary landforms (segments, facets, relief units) are the smallest homogeneous divisions of the land surface, at the given scale/resolution. These are areas with relatively homogeneous morphometric properties, bounded by lines of discontinuity. A plateau or a hill can be observed at various scales ranging from few hundred meters to hundreds of kilometers. Hence, the spatial distribution of landforms is often scale-dependent as is the case for soils and geological strata.
A number of factors, ranging from plate tectonics to erosion and deposition, can generate and affect landforms. Biological factors can also influence landforms— for example, note the role of vegetation in the development of dune systems and salt marshes, and the work of corals and algae in the formation of coral reefs.
Many of the terms are not restricted to refer to features of the planet Earth, and can be used to describe surface features of other planets and similar objects in the Universe. Examples are mountains, hills, polar caps, and valleys, which are found on all of the terrestrial planets.
Landforms may be extracted from a digital elevation model using some automated techniques where the data has been gathered by modern satellites and stereoscopic aerial surveillance cameras. Until recently, compiling the data found in such data sets required time consuming and expensive techniques involving many man-hours. The most detailed DEMs available are measured directly using LIDAR techniques. In 2013 Bangs et al. demonstrated the inherent differences in so-called 5 meter resolution DEMs using sources of higher and lower resolution.
- Robert A. MacMillan, David H. McNabb, R. Keith Jones (September 2000). "Conference paper: "Automated landform classification using DEMs"". Retrieved 2008-06-26.
- Bangs, D.E., Aspinall, J.D., Sweeney, S.J., Duncan, M.R., Lepp, S., Schuyler, B., 2013. Implications of three-dimensional agricultural landscape representation resolution on understanding the relationships between soil variability and crop yield: an example from Norfolk County, Ontario.Presented at the EOGC and CIG Annual Conference in Toronto. Paper #73.
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