A ridge is a long, narrow, elevated geomorphology landform, structural feature, or a 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, , Tectonics, or a combination of these in origin and can consist of either bedrock, 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,
Aeolian ridge
Coastal ridges
- Beach ridge
- 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 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
- 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 , flatirons, , and hogbacks.
Glacial ridges
- Moraines and eskers
- Glacier activity may leave ridges in the form of and . An arête is a thin ridge of rock that is formed by glacial erosion.
- Pressure ridge (ice)
- 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
- Oceanic spreading ridge
- 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. Isostasy settling and erosion gradually reduces the elevations moving away from the zone.
- Impact crater
- Large asteroid strikes typically form large 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
- Volcanic crater/caldera ridges
- Large often have a central volcanic crater or caldera or both, bordered by rims that form circular ridges.
See also
