Ridge

A ridge is a long, narrow, elevated geomorphologic landform, 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, 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.[1][2][3]

This article is about the geography and geology concept. For other uses, see Ridge (disambiguation).
"Ridgeline" redirects here. For other uses, see Ridgeline (disambiguation).
A mountain ridge in Japan
A stratigraphic ridge within the Appalachian Mountains.
The edges of tuyas can form ridges.
Pirin Mountain main ridge – view from Koncheto knife-edge ridge towards the pyramidal peaks Vihren and Kutelo

Types
The Pyynikki Ridge in Tampere, Finland

There are several main types of 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.
Stratigraphic ridge
In places such as the Ridge-and-Valley Appalachians, long, even, straight ridges are formed because they are the uneroded remaining edges of the more resistant dipping strata that were folded laterally. Similar ridges have formed in places such as the Black Hills, where the ridges form concentric circles around the igneous core. These ridges are sometimes called hogback 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. Isostatic settling and erosion gradually reduces the elevations moving away from the zone.
Crater ridges
Large meteorite strikes typically form large impact craters bordered by circular ridges.
Volcanic crater/caldera ridges
Large volcanoes often leave behind a central crater/caldera bordered by circular ridges.
Fault ridges
Faults often form escarpments. Sometimes the tops of the escarpments form not plateaus but slope back so that the edges of the escarpments form ridges.
Dune ridges
In areas of large-scale dune activity, certain types of dunes result in sand ridges.
Moraines and eskers
Glacial activity may leave ridges in the form of moraines and eskers. An arête is a thin ridge of rock that is formed by glacial erosion.
Volcanic subglacial ridges
Many subglacial volcanoes create ridge-like formations when lava erupts through a thick glacier or ice sheet.
Shutter ridges
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.
Pressure ridge (lava)
A specific case of pressure ridge, 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.[4] An ice pressure ridge develops in an ice cover as a result of a stress regime established within the plane of the ice.

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[5] and the San Rafael Reef. The usage may have originated with sailors during the Australian gold rushes to describe the gold-bearing ridges of Bendigo, Australia.[6]

See also
Wikimedia Commons has media related to Ridges.

References
  1. Nystuen, J.P. (ed.). Rules and recommendations for naming geological units in Norway, Norsk Geologisk Tidsskrift 69, supplement 2. Oslo, Norway. p. 111.
  2. Huggett, R.J. (2011). Fundamentals of geomorphology (3rd ed.). New York, New York: Routledge. p. 516. ISBN 978-0203860083.
  3. Neuendorf, K.K.E.; Mehl, J.P. Jr.; Jackson, J.A., eds. (2005). Glossary of Geology (5th ed.). Alexandria, Virginia: American Geological Institute. p. 554. ISBN 978-0922152896.
  4. "How Volcanoes Work - lava flow features". www.geology.sdsu.edu. Retrieved 2019-01-13.
  5. "Capitol Reef National Park – Geology". Capitol Reef National Park web site. U.S. National Park Service. 2007. Retrieved January 17, 2009.
  6. Van Cott, John W. (1990). Utah place names : a comprehensive guide to the origins of geographic names : a compilation. Salt Lake City, Utah: University of Utah Press. p. 65. ISBN 9780874803457. Retrieved 2 June 2022.
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