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 ?
Conservationists say dunes are naturally mobile and need to be moving to be effective habitats.
Nicola Hutchinson, from wildlife charity Plantlife, said: "This project will radically revitalise our ailing dunes and the wealth of wildflowers they harbour."
Looking closely at sand formation gives scientists an idea on factors such as Martian winds, the planet's thin atmosphere, temperature and also how topography affects the sand dunes on Planet Mars.
He noted that tourists had come from neighbouring countries to join in the Khawa Dune challenge festivities.
Checkpoint activations included Gulf News Reach handing out fresh juices and refreshments to Al Jazira Poultry Farm handing out eggs to weary travellers for a quick snack to recharge before attempting to conquer some of the UAE's highest sand dunes.
Villeneuve confirmed plans to adapt 'Dune' for film during an interview with Quebec publication La Presse, published May 9.
"Sand dunes by their very nature are notoriously unstable and digging large holes or tunnels in them can be extremely dangerous or even fatal.
Some Dunites, including Carl Beckstead, even moved to Halcyon later in life; others, such as Ella Young, lived in Halcyon while continuing to maintain the "Dunite Philosophy." As Gavin Arthur firmly believed and reiterated in his publication, the Dune Forum, the physical location of a person was not what determined whether he or she could be considered a "Dunite." Instead, the dunes were "symbolic of a state of mind, open, untrammeled by the cross-currents of metropolitan life." (37) In many ways, members of the Halcyon community represented this state of mind, as they continued their own social experiment within their communal experiment.
We set off straight ahead, following the very visible path through the sand as it curved here and there through the grassy dune bluffs.
The previous day, a ranger had told me that if I walked to the end of the creek, Star Dune's distinctive ridges would be in plain sight.
Dune's next product, which recently earned a EUR 3m grant from the EC 2020 Horizon program, will expand the company's surgical oncology portfolio to include a soft tissue biopsy system with its first indication in breast tissue.