dune

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dune,

mound or ridge of wind-blown sand formed in arid regions and along coasts. Dunes are common in most of the great deserts of the world. Often a dune begins to form because material is deposited by the wind as it encounters a bush, a rock, or other obstacle to impede its flow. Dunes that are not stabilized by vegetation have a tendency to migrate, driven by the prevailing wind. These free-moving dunes are of two main kinds, transverse and longitudinal, and the characteristic form is maintained in migration. Transverse dunes usually form where wind blows quite constantly from one direction across expanses of loose sand; the windward slope is typically gentle, and the lee side, where the sand blown over the crest seeks its natural angle of repose, is steep. Such dune ridges have a tendency, especially with increasing distance from the source of sand, to break up into individual small hills. One of the commonest forms of these hills is the symmetrical, crescent-shaped, transverse dune called a barkhan; examples can be found at Pismo Beach, Calif., and near Arequipa, Peru. Longitudinal dunes are ridges, with about the same slope on both sides, elongated in the direction of the prevailing wind. They are especially well developed in the African deserts and are also seen in Arizona and in the Imperial Valley, Calif. Coastal blowout dunes, which are approximately U-shaped with their open ends upwind, form along shores where vegetation cover is locally broken. Examples are the dunes along the southern and eastern shores of Lake Michigan. Dunes reaching a height of more than 500 ft (150 m) exist in the Great Sand Dunes National Park and Preserve, Colo.; gleaming white dunes of gypsum sand are formed in White Sands National Park, N.Mex. Sand dunes may cause destruction as they migrate; in France on the coast of the Bay of Biscay they destroyed villages and farmland. In some areas of Europe and the United States this danger has been checked by planting vegetation and by erecting barriers. One value of dunes is their absorption of rain, which helps to raise the level of the water table and thus produces oases in some areas and provides accessible sources of water through rather shallow wells.
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dune

[dün]
(geology)
A mound or ridge of unconsolidated granular material, usually of sand size and of durable composition (such as quartz), capable of movement by transfer of individual grains entrained by a moving fluid.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

dune

a mound or ridge of drifted sand, occurring on the sea coast and in deserts
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Sand dunes are home to rare plants and animals, but these important habitats have declined by a third since 1900 in the UK.
Using the funding, government conservation agency Natural England has teamed up with the National Trust, Plantlife, The Wildlife Trusts and Natural Resources Wales to create more dynamic sand dune landscapes.
The area is characterised by the presence of high sand dunes. The area also is believed to be similar to Savanna environment which made it an attractive place for inhabitants before it went dry.
space agency NASA's MRO HiRise camera team based in the University of Arizona showcases a unique sand dune formation that pretty much looks like the Starfleet logo of the hugely popular sci-fi franchise.
Jalil, an expatriate, said that young people love to come to the Sealine area to enjoy the beautiful landscape, especially the unique combination of sand dunes and sea.
Police determined that he had fallen asleep for a few seconds before the car swerved into the sand dunes and flipped over several times.
Officials flatten sand dunes to check reckless off-roaders
According to the researchers, this ancient sand would be an excellent place to search for the molecular evidence of life on Mars, as sand dunes on Earth have been shown to support microbial life.
While the town saw an inch or two, the sand dunes on its outskirts were covered in snow.
The winning photo of sand dunes at West Wittering BENJAMIN GRAHAM
Sand dunes are a threatened habitat in Wales, and the dunes at Whitford are home to some really quite scarce species.
Then, a friend in Boulder told me about her family's trip to see the giant sand dunes at a little-known national park just north of the New Mexico border.