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For other uses, see Dune (disambiguation).
Erg Chebbi, Morocco



Dunes also form under the action of water flow (fluvial processes), and on sand or gravel beds of rivers, estuaries and the sea-bed.

The modern word "dune" came into English from French circa 1790. In ancient times, words cognate to "dune" probably had the meaning of a built-up hill or citadel fortification.[1]


Dune habitats provide niches for highly specialised plants and animals, including numerous rare species and some endangered species. Due to widespread human population expansion, dunes face destruction through land development and recreational usages, as well as alteration to prevent the encroachment of sand onto inhabited areas. Some countries, notably the United States, Australia, Canada, New Zealand, the United Kingdom, and Netherlands, have developed significant programs of dune protection through the use of sand dune stabilization. In the U.K., a Biodiversity Action Plan has been developed to assess dunes loss and to prevent future dunes destruction.

Dune en.svg

Aeolian dune shapes[edit]


"Crescent-shaped mounds are generally wider than they are long. The slipfaces are on the concave sides of the dunes. These dunes form under winds that blow consistently from one direction, and they also are known as barchans, or transverse dunes. Some types of crescentic dunes move more quickly over desert surfaces than any other type of dune. A group of dunes moved more than 100 metres per year between 1954 and 1959 in the China's Ningxia Province, and similar speeds have been recorded in the Western Desert of Egypt. The largest crescentic dunes on Earth, with mean crest-to-crest widths of more than 3 kilometres, are in China's Taklamakan Desert."[2]


"Straight or slightly sinuous sand ridges typically much longer than they are wide are known as linear dunes. They may be more than 160 kilometres (100 miles) long. Some linear dunes merge to form Y-shaped compound dunes. Many form in bidirectional wind regimes. The long axes of these dunes extend in the resultant direction of sand movement."[3]

Linear loess hills known as pahas are superficially similar. These hills appear to have been formed during the last ice age under permafrost conditions dominated by sparse tundra vegetation.




Oval or circular mounds that generally lack a slipface. Dome dunes are rare and occur at the far upwind margins of sand seas.


U-shaped mounds of sand with convex noses trailed by elongated arms are parabolic dunes. These dunes are formed from blowout dunes where the erosion of vegetated sand leads to a U-shaped depression. The elongated arms are held in place by vegetation; the largest arm known on Earth reaches 12 km. Sometimes these dunes are called U-shaped, blowout, or hairpin dunes, and they are well known in coastal deserts. Unlike crescent shaped dunes, their crests point upwind. The bulk of the sand in the dune migrates forward.

In plan view, these are U-shaped or V-shaped mounds of well-sorted, very fine to medium sand with elongated arms that extend upwind behind the central part of the dune. There are slip faces that often occur on the outer side of the nose and on the outer slopes of the arms.

These dunes often occur in semiarid areas where the precipitation is retained in the lower parts of the dune and underlying soils. The stability of the dunes was once attributed to the vegetative cover but recent research has pointed to water as the main source of parabolic dune stability. The vegetation that covers them—grasses, shrubs, and trees—help anchor the trailing arms. In inland deserts, parabolic dunes commonly originate and extend downwind from blowouts in sand sheets only partly anchored by vegetation. They can also originate from beach sands and extend inland into vegetated areas in coastal zones and on shores of large lakes.

Most parabolic dunes do not reach heights higher than a few tens of metres except at their nose, where vegetation stops or slows the advance of accumulating sand.

Simple parabolic dunes have only one set of arms that trail upwind, behind the leading nose. Compound parabolic dunes are coalesced features with several sets of trailing arms. Complex parabolic dunes include subsidiary superposed or coalesced forms, usually of barchanoid or linear shapes.

Parabolic dunes, like crescent dunes, occur in areas where very strong winds are mostly unidirectional. Although these dunes are found in areas now characterized by variable wind speeds, the effective winds associated with the growth and migration of both the parabolic and crescent dunes probably are the most consistent in wind direction.

The grain size for these well-sorted, very fine to medium sands is about 0.06 to 0.5 mm. Parabolic dunes have loose sand and steep slopes only on their outer flanks. The inner slopes are mostly well packed and anchored by vegetation, as are the corridors between individual dunes. Because all dune arms are oriented in the same direction, and, the inter-dune corridors are generally swept clear of loose sand, the corridors can usually be traversed in between the trailing arms of the dune. However to cross straight over the dune by going over the trailing arms, can be very difficult. Also, traversing the nose is very difficult as well because the nose is usually made up of loose sand without much if any vegetation.

A type of extensive parabolic dune that lacks discernible slip faces and has mostly coarse grained sand is known as a Zibar.[4] The term zibar comes from the Arabic word to describe "rolling transverse ridges ... with a hard surface".[5] The dunes are small, have low relief, and can be found in many places across the planet from Wyoming to Saudi Arabia to Australia. Spacing between zibars ranges from 50 to 400 meters and they don't become more than 10 meters high.[6] The dunes form at about ninety degrees to the prevailing wind which blows away the small, fine-grained sand leaving behind the coarser grained sand to form the crest.[7]

Longitudinal (Seif) dunes[edit]

Longitudinal dunes (also called Seif dunes, after the Arabic word for "sword"), elongate parallel to the prevailing wind, possibly caused by a larger dune having its smaller sides blown away. Seif dunes are sharp-crested and are common in the Sahara. They range up to 300 m (980 ft) in height and 300 km (190 mi) in length. In the southern third of the Arabian Peninsula, a vast erg called the Rub' al Khali or the Empty Quarter, contains seif dunes that stretch for almost 200 km and reach heights of over 300 m.



Reversing dunes[edit]



Sub-aqueous dunes[edit]




Lithified dunes[edit]

A lithified (consolidated) sand dune is a type of sandstone that is formed when a marine or aeolian sand dune becomes compacted and hardened. Once in this form, water passing through the rock can carry and deposit minerals, which can alter the color of the rock. Cross-bedded layers of stacks of lithified dunes can produce the cross-hatching patterns, such as those seen in the Zion National Park in the western United States.

A slang term that is used in the Southwestern States (of the U.S.A.) for those consolidated and hardened sand dunes is "slickrock", a name that was introduced by pioneers of the Old West because their steel-rimmed wagon wheels could not gain traction on the rock.

Coastal dunes[edit]

Dunes form where constructive waves encourage the accumulation of sand, and where prevailing onshore winds blow this sand inland. There need to be obstacles—for example, vegetation, pebbles and so on—to trap the moving sand grains. As the sand grains get trapped they start to accumulate, starting dune formation. The wind then starts to affect the mound of sand by eroding sand particles from the windward side and depositing them on the leeward side. Gradually this action causes the dune to "migrate" inland, as it does so it accumulates more and more sand. Dunes provide privacy and shelter from the wind.

Ecological succession on coastal dunes[edit]

As a dune forms, plant succession occurs. The conditions on an embryo dune are harsh, with salt spray from the sea carried on strong winds. The dune is well drained and often dry, and composed of calcium carbonate from seashells. Rotting seaweed, brought in by storm waves adds nutrients to allow pioneer species to colonize the dune. These pioneer species are marram grass, sea wort grass and other sea grasses in the United Kingdom. These plants are well adapted to the harsh conditions of the foredune typically having deep roots which reach the water table, root nodules that produce nitrogen compounds, and protected stoma, reducing transpiration. Also, the deep roots bind the sand together, and the dune grows into a foredune as more sand is blown over the grasses. The grasses add nitrogen to the soil, meaning other, less hardy plants can then colonize the dunes. Typically these are heather, heaths and gorses. These too are adapted to the low soil water content and have small, prickly leaves which reduce transpiration. Heather adds humus to the soil and is usually replaced by coniferous trees, which can tolerate low soil pH, caused by the accumulation and decomposition of organic matter with nitrate leaching.[9] Coniferous forests and heathland are common climax communities for sand dune systems.



Main article: Desertification

Sand dunes can have a negative impact on humans when they encroach on human habitats. Sand dunes move via a few different means, all of them helped along by wind. One way that dunes can move is by saltation, where sand particles skip along the ground like a bouncing ball. When these skipping particles land, they may knock into other particles and cause them to move as well, in a process known as creep. With slightly stronger winds, particles collide in mid-air, causing sheet flows. In a major dust storm, dunes may move tens of metres through such sheet flows. Also as in the case of snow, sand avalanches, falling down the slipface of the dunes—that face away from the winds—also move the dunes forward.

Sand threatens buildings and crops in Africa, the Middle East, and China. Drenching sand dunes with oil stops their migration, but this approach is quite destructive to the dunes' animal habitats and uses a valuable resource. Sand fences might also slow their movement to a crawl, but geologists are still analyzing results for the optimum fence designs.[citation needed] Preventing sand dunes from overwhelming towns, villages, and agricultural areas has become a priority for the United Nations Environment Programme. Planting dunes with vegetation also helps to stabilise them.



Wind ripples on crescent-shaped sand dunes (Barchans) in Southwest Afghanistan (Sistan).



North America[edit]

South America[edit]


World's highest dunes[edit]

Note: This table is partially based on estimates and incomplete information.
Dune Height from Base feet/metres Height from Sea Level feet/metres Location Notes
Duna Federico Kirbus ~4,035/1,230 ~9,334/2,845 Bolsón de Fiambalá, Fiambalá, Catamarca Province, Argentina Highest in the world[16]
Cerro Blanco ~3,860/1,176 ~6,791/2,080 Nasca Valley, Department of Ica, Peru 14°52′05″S 74°50′17″W﻿ / ﻿14.868°S 74.838°W﻿ / -14.868; -74.838﻿ (Cerro Blanco Dune) Highest in Peru, second highest in the world
Badain Jaran Dunes ~1,640/500 ~6,640/2,020 Badain Jaran Desert, Alashan Plain, Inner Mongolia, Gobi Desert, China World's tallest stationary dunes and highest in Asia[17]
Rig-e Yalan Dune ~1,542/470 ~3,117/950 Lut Desert, Kerman, Iran Near World the hottest place (Gandom Beryan)
Average Highest Area Dunes 1,410/430? ~6,500/~1,980? Isaouane-n-Tifernine Sand Sea, Algerian Sahara Highest in Africa
Big Daddy/Dune 7
(Big Mama?)[18]
1,256/383 ~1,870/570 Sossusvlei Dunes, Namib Desert, Namibia / Near Walvis Bay Namib Desert, Namibia according to the Namibian Ministry of Environment & Tourism the highest dune in the world
Mount Tempest ~920/280 ~920/280 Moreton Island, Brisbane, Australia Highest in Australia
Medanoso Dune ~1805/550 ~5446/1,660 Atacama Desert, Chile Highest in Chile

Sand dune systems[edit]

(coastal dunes featuring succession)

Extraterrestrial dunes[edit]

Sand dune on Mars

Dunes can likely be found in any environment where there is a substantial atmosphere, winds, and dust to be blown. Dunes are common on Mars and in the equatorial regions of Titan.

Titan's dunes include large expanses with modal lengths of about 20–30 km. The regions are not topographically confined, resembling sand seas. These dunes are interpreted to be longitudinal dunes whose crests are oriented parallel to the dominant wind direction, which generally indicates west-to-east wind flow. The sand is likely composed of hydrocarbon particles, possibly with some water ice mixed in.[19]

See also[edit]


  1. ^ dune - Definitions from Dictionary.com
  2. ^ "Types of Dunes". Retrieved 8 March 2012. 
  3. ^ "Types of Dunes". Retrieved 23 May 2014. 
  4. ^ Goudie, Ron Cooke; Andrew Warren; Andrew (1996). Desert geomorphology (2. impr. ed.). London: UCL Press. pp. 395–396. ISBN 1-85728-017-2. 
  5. ^ Goudie, Ron Cooke; Andrew Warren; Andrew (1996). Desert geomorphology (2. impr. ed.). London: UCL Press. p. 395. ISBN 1-85728-017-2. 
  6. ^ "USGS Landform Glossary". United States Geological Survey. Retrieved 3 October 2013. 
  7. ^ Nielsen, Ole. "Zibar Dunes". My Opera. Retrieved 3 October 2013. 
  8. ^ Prothero, D. R. and Schwab, F., 1996, Sedimentary Geology, pg. 45–49, ISBN 0-7167-2726-9
  9. ^ Miles, J. (1985). "The pedogenic effects of different species and vegetation types and the implications of succession". European Journal of Soil Science 36 (4): 571. doi:10.1111/j.1365-2389.1985.tb00359.x. 
  10. ^ "Alexandria Coastal Dunefields". UNESCO World Heritage. Retrieved 11 January 2010. 
  11. ^ Sossusvlei
  12. ^ Wahiba Sands
  13. ^ Mann, D. H.; Heiser P. A.; Finney B. P. (2002). "Holocene history of the Great Kobuk Sand Dunes, Northwestern Alaska". Quaternary Science Reviews (Elsevier) 21 (4): 709–731. doi:10.1016/S0277-3791(01)00120-2. 
  14. ^ Smith, S. & Mark, S. (2006). Alice Gray, Dorothy Buell, and Naomi Svihla: "Preservationists of Ogden Dunes". The South Shore Journal, 1. http://www.southshorejournal.org/index.php/issues/volume-1-2006/78-journals/vol-1-2006/117-alice-gray-dorothy-buell-and-naomi-svihla-preservationists-of-ogden-dunes
  16. ^ Sandboard Magazine
  17. ^ "Mystery of world's tallest sand dunes solved" - 24 November 2004 - New Scientist
  18. ^ Big Mama highest dune
  19. ^ Peeking Through the Haze: Titan's Surface, part II - The Planetary Society Blog | The Planetary Society


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