In the
earth sciences and
geology sub-fields, a
landform or
physical feature comprises a
geomorphological unit, and is largely defined by its surface form and location in the landscape, as part of the
terrain, and as such, is typically an element of
topography. Landform elements also include seascape and oceanic waterbody interface features such as
bays,
peninsulas,
seas and so forth, including sub-surface terrain features such as submersed
mountain ranges, volcanoes, and the great ocean basins under the thin skin of water, for the whole earth is the province and domain of geology.
Physical characteristics
Landforms are categorised 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, 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 of many man-hours.
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 homogenous
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.
Landforms do not include man-made features, such as
canals,
ports and many
harbors; and geographic features, such as
deserts,
forests,
grasslands, and impact
craters.
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, polar caps, and valleys, which are found on all of the
terrestrial planets.
See also
