Ridge (other)
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A ridge is a long, narrow, elevated
geomorphologic Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or n ...
landform A landform is a natural or anthropogenic land feature on the solid surface of the Earth or other planetary body. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography. Landforms include hills, ...
, structural feature, or combination of both separated from the surrounding terrain by steep sides. The sides of a ridge slope away from a narrow top, the crest or ridgecrest, with the terrain dropping down on either side. The crest, if narrow, is also called a ridgeline. Limitations on the dimensions of a ridge are lacking. Its height above the surrounding terrain can vary from less than a meter to hundreds of meters. A ridge can be either depositional, erosional, tectonic, or combination of these in origin and can consist of either
bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...
, loose sediment, lava, or ice depending on its origin. A ridge can occur as either an isolated, independent feature or part of a larger geomorphological and/or structural feature. Frequently, a ridge can be further subdivided into smaller geomorphic or structural elements.


Classification

As in the case of landforms in general, there is a lack of any commonly agreed classification or typology of ridges. They can be defined and classified on the basis of a variety of factors including either genesis, morphology, composition, statistical analysis of remote sensing data, or some combinations of these factors. An example of ridge classification is that of Schoeneberger and Wysocki, which provides a relatively simple and straightforward system that is used by the USA National Cooperative Soil Survey Program to classify ridges and other landforms. This system uses the dominant geomorphic process or setting to classify different groups of landforms into two major groups, ''Geomorphic Environments'' and ''Other Groupings'' with a total of 16 subgroups. The groups and their subgroups are not mutually exclusive; landforms, including ridges, can belong to multiple subgroups. In this classification, ridges are found in the Aeolian, Coastal Marine and Estuarine, Lacustrine, Glacial, Volcanic and Hydrothermal, Tectonic and Structural, Slope, and Erosional subgroups.


Aeolian ridge

; Aeolian dune ridge: An aeolian dune ridge is a ridge of sand piled up by the wind. A sand dune can be either a hill or ridge of sand piled up by the wind. A single sand dune can range in length from less than one meter to several tens of kilometers, their height can vary from a few tens of centimeters to a 150 meters. ''Megadunes'' or ''draas'' are very large dunes, which can have smaller dunes superimposed on them.


Coastal ridges

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Beach ridge A beach ridge is a wave-swept or wave-deposited ridge running parallel to a shoreline. It is commonly composed of sand as well as sediment worked from underlying beach material. The movement of sediment by wave action is called ''littoral tra ...
: A beach ridge is a low, essentially continuous ridge of beach or beach-and-dune sediments piled up by the action of waves and currents on a shoreline beyond the present limit of storm waves and the reach of ordinary tides. They occur occurring singly or as one of a series of approximately parallel ridges that are roughly parallel to the shoreline.


Erosional ridges

;
Dendritic Dendrite derives from the Greek word "dendron" meaning ( "tree-like"), and may refer to: Biology *Dendrite, a branched projection of a neuron *Dendrite (non-neuronal), branching projections of certain skin cells and immune cells Physical * Dendr ...
ridge: In typical dissected plateau terrain, the stream drainage valleys will leave intervening ridges. These are by far the most common ridges. These ridges usually represent slightly more erosion resistant rock, but not always – they often remain because there were more joints where the valleys formed or other chance occurrences. This type of ridge is generally somewhat random in orientation, often changing direction frequently, often with knobs at intervals on the ridge top. ;
Strike ridge In structural geology, a homocline or homoclinal structure (from old el, homo = same, cline = inclination), is a geological structure in which the layers of a sequence of rock strata, either sedimentary or igneous, dip uni ...
: A strike ridge is an asymmetric ridge created by the differential erosion of a hard, erosion-resistant, dipping layer of rock sandwiched between layers of weaker, more easily eroded rock. A strike ridge has a distinctly gentler sloping side (dip slope), that roughly parallels the inclined layer of erosion-resistant rock. The opposite side of a strike ridge is relatively short, steep or cliff-like slope (scarp slope) that cuts across the tilted layers of rocks. In foldbelts such as the Ridge-and-Valley Appalachians, they form series of long, parallel, straight to arcuate ridges. Strike ridges are subdivided into cuestas, flatirons, homoclinal ridges, and hogbacks. ;Reef: A term applied by early explorers and settlers in the western United States to ridges that formed a rocky barrier to land travel, by analogy with ocean reefs as barriers to sea travel. Examples include Capitol Reef National Park and the San Rafael Reef. The usage may have originated with sailors during the
Australian gold rushes During the Australian gold rushes, starting in 1851, significant numbers of workers moved from elsewhere in Australia and overseas to where gold had been discovered. Gold had been found several times before, but the colonial government of Ne ...
to describe the gold-bearing ridges of Bendigo, Australia.


Glacial ridges

;Moraines and eskers: Glacial activity may leave ridges in the form of
moraine A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice shee ...
s and eskers. An arête is a thin ridge of rock that is formed by glacial erosion. ;
Pressure ridge (ice) A pressure ridge, when consisting of ice, is a linear pile-up of sea ice fragments formed in pack ice by accumulation in the convergence between floes. Such a pressure ridge develops in an ice cover as a result of a stress regime established wi ...
: An ice pressure ridge is a ridge of deformed ice along the boundaries of individual ice floes when the ice floes on a lake or ocean collide and compress their edges. The average height of a sea ice pressure ridge is between 5 and 30 meters.


Tectonic and Structural ridges

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Oceanic spreading ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a diverge ...
: In tectonic spreading zones around the world, such as at the Mid-Atlantic Ridge, the volcanic activity forms new land between tectonic boundaries creating volcanic ridges at the spreading zone. Isostatic settling and erosion gradually reduces the elevations moving away from the zone. ; Impact Crater ridge: Large
asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...
strikes typically form large impact craters bordered by rim(s) that are circular ridge(s). ; Shutter ridge: A shutter ridge is a ridge that has moved along a fault line, blocking or diverting drainage. Typically, a shutter ridge creates a valley corresponding to the alignment of the fault that produces it.


Volcanic and Hydrothermal ridges

; Pressure ridge (lava): A specific case of
pressure ridge A pressure ridge is a topographic ridge produced by compression. Depending on the affected material, "pressure ridge" may refer to: * Pressure ridge (ice), between ice floes * Pressure ridge (lava), in a lava flow * Pressure ridge (seismic), in ...
, also known as a ''tumulus'', usually develops in lava flows, especially when slow-moving lava beneath a solidified crust wells upward. The brittle crust usually buckles to accommodate the inflating core of the flow, thus creating a central crack along the length of the tumulus. ;Volcanic crater/caldera ridges: Large volcanoes often have a central
crater Crater may refer to: Landforms *Impact crater, a depression caused by two celestial bodies impacting each other, such as a meteorite hitting a planet *Explosion crater, a hole formed in the ground produced by an explosion near or below the surfac ...
or
caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...
or both, bordered by rims that form circular ridges. ;Volcanic subglacial ridges: Subglacial volcanic eruptions can create volcanic ridges, known as '' tindars'', that vary from tens of meters up to 250 meters in height. Tindars are a piles of volcanic ash that have been generated by explosive subaqueous eruptions in a glacial meltwater-filled vault or lake within a glacier or ice sheet.


See also

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References

{{Reflist Montane ecology Erosion landforms Slope landforms Ridges Oronyms