![Vihren Pirin IMG 0859](https://upload.wikimedia.org/wikipedia/commons/3/37/Vihren_Pirin_IMG_0859.jpg)
A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The lines along the crest formed by the highest points, with the terrain dropping down on either side, are called the ridgelines. Ridges are usually termed
hill
A hill is a landform that extends above the surrounding terrain. It often has a distinct summit.
Terminology
The distinction between a hill and a mountain is unclear and largely subjective, but a hill is universally considered to be not a ...
s or
mountain
A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually highe ...
s as well, depending on size. Smaller ridges, especially those leaving a larger ridge, are often referred to as spurs.
Types
![Pyynikki ridge4](https://upload.wikimedia.org/wikipedia/commons/e/e9/Pyynikki_ridge4.jpg)
There are several main types of 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
A dissected plateau is a plateau area that has been severely eroded such that the relief is sharp. Such an area may be referred to as mountainous, but dissected plateaus are distinguishable from orogenic mountain belts by the lack of folding, ...
terrain, the stream drainage valleys will leave intervening ridges. These are by far the most common ridges. These ridges usually represent slightly more
erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...
resistant rock, but not always – they often remain because there were more
joints
A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...
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
The Ridge-and-Valley Appalachians, also called the Ridge and Valley Province or the Valley and Ridge Appalachians, are a physiographic province of the larger Appalachian division and are also a belt within the Appalachian Mountains extending ...
, 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
The Black Hills ( lkt, Ȟe Sápa; chy, Moʼȯhta-voʼhonáaeva; hid, awaxaawi shiibisha) is an isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, United States. Black ...
, where the ridges form concentric circles around the
igneous
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...
core. These ridges are sometimes called
hogback ridges.
;
Oceanic spreading ridge: In
tectonic
Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...
spreading zones around the world, such as at the
Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates the North ...
, 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 crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact crater ...
s bordered by circular ridges.
;Volcanic crater/caldera ridges: Large
volcano
A volcano is a rupture in the Crust (geology), crust of a Planet#Planetary-mass objects, planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and volcanic gas, gases to escape from a magma chamber below the surface.
On Ear ...
es often leave behind a central
crater/
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 ...
bordered by circular ridges.
;Fault ridges:
Faults often form
escarpment
An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations.
The terms ''scarp'' and ''scarp face'' are often used interchangeably with ''esca ...
s. 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
Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class o ...
ridges.
;Moraines and eskers:
Glacial
A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betwe ...
activity may leave ridges in the form of
moraines and
esker
An esker, eskar, eschar, or os, sometimes called an ''asar'', ''osar'', or ''serpent kame'', is a long, winding ridge of stratified sand and gravel, examples of which occur in glaciated and formerly glaciated regions of Europe and North Ame ...
s. An
arête
An arête ( ) is a narrow ridge of rock which separates two valleys. It is typically formed when two glaciers erode parallel U-shaped valleys. Arêtes can also form when two glacial cirques erode headwards towards one another, although frequ ...
is a thin ridge of rock that is formed by glacial erosion.
;Volcanic subglacial ridges: Many
subglacial volcanoes create ridge-like formations when
lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
erupts through a thick glacier or
ice sheet
In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at La ...
.
;
Shutter ridge A shutter ridge is a ridge which 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. Shutter ridges occur exclusively at strike- ...
s: 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)
In volcanology, a pressure ridge or a tumulus (plural: tumuli), and rarely referred to as a schollendome, is sometimes created in an active lava flow. Formation occurs when the outer edges and surfaces of the lava flow begin to harden. If the ad ...
: A specific case of
pressure ridge, also known as a
tumulus
A tumulus (plural tumuli) is a mound of earth and stones raised over a grave or graves. Tumuli are also known as barrows, burial mounds or ''kurgans'', and may be found throughout much of the world. A cairn, which is a mound of stones bu ...
, 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. 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
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes—deposition of sand, wave erosion planing down rock out ...
as barriers to sea travel. Examples include
Capitol Reef National Park
Capitol Reef National Park is an American national park in south-central Utah. The park is approximately long on its northsouth axis and just wide on average. The park was established in 1971 to preserve of desert landscape and is open all ye ...
and the
San Rafael Reef
The San Rafael Reef is a geologic feature located in Emery County in central Utah, part of the Colorado Plateau. Approximately 75 miles (120 km) long, it is the name given to the distinctive eastern edge of the San Rafael Swell. Composed pr ...
. The usage may have originated with sailors during the
Australian gold rushes to describe the gold-bearing ridges of
Bendigo, Australia
Bendigo ( ) is a city in Victoria, Australia, located in the Bendigo Valley near the geographical centre of the state and approximately north-west of Melbourne, the state capital.
As of 2019, Bendigo had an urban population of 100,991, maki ...
.
See also
*
*
*
Interlocking spur
An interlocking spur, also known as an overlapping spur, is one of any number of projecting ridges that extend alternately from the opposite sides of the wall of a young, V-shaped valley down which a river with a winding course flows. Each of t ...
*
*
*
Ridge detection
In image processing, ridge detection is the attempt, via software, to locate ridges in an image, defined as curves whose points are local maxima of the function, akin to geographical ridges.
For a function of ''N'' variables, its ridges are ...
*
Ridge (differential geometry)
In differential geometry, a smooth surface in three dimensions has a ridge point when a line of curvature has a local maximum or minimum of principal curvature. The set of ridge points form curves on the surface called ridges.
The ridges of a g ...
*
References
{{Reflist
External links
Norsk Geologisk Tidsskrift Volume 69 Universitetsforlaget, 1989, page 40 https://books.google.com/books?id=dXK7AAAAIAAJ
Physical Geography: Introduction To Earth page 164
Montane ecology
Erosion landforms
Slope landforms
Ridges
A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The line ...
Oronyms