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 Monument, 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.

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.

dune

a mound or ridge of drifted sand, occurring on the sea coast and in deserts
References in periodicals archive ?
Playing the game as Cara, the user is propelled along sand dunes in an attempt to outrun a sand storm, along the way you can collect stars and bonuses to boost your score.
In March, a Bedlington man was trapped beneath sand when a dune he had been digging in collapsed on him at Druridge Bay.
Terry Clark, White Marlin's President and CEO commented, "The acquisition of these core producing properties from Dune Energy is another step forward in our plan to increase investor value and net income from our Texas and Louisiana Gulf Coast strategic asset focus.
Two types of dune protecting systems installed (to guard against trampling); and
London, January 13 ( ANI ): A study has revealed how prevailing winds create sand dunes on Earth.
When a dune grows to about 100 meters long, it amasses enough sand on its upwind side for an incipient dune to develop.
The 2,500 square feet store features the new retail concept from Dune London.
tv, a global provider of HTML5 set-top box (STB) software and Dune HD, a global leader in full HD media players and connected boxes, announce a new cost-effective consumer platform aimed at carriers and retailers.
These are an ideal seed bed for rare plants and are home to endangered dune insects.
Today, the warren is home to a number of plants and invertebrates which specialise in the dune environment.
IT AIN'T HEAVY: Six-year-old Luke Hilton treks up the dunes with his tree
At Kenfig, Bridgend, just 2% of the dune system is now bare sand, down from about 40% in the mid 1940s.