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 ?
NASA's Mars Reconnaissance Orbiter (MRO) has revealed that movement in sand dune fields on the Red Planet occurs on a surprisingly large scale, about the same as in dune fields on Earth.
Large variation of edaphic and climatic conditions in dune fields has brought about a large variation also in the functioning and structure of the forest ecosystem, including the physiological status of Scots pine.
The southern Strait of Georgia dune field consists of large subaqueous, symmetrical dunes that have wavelengths of 150 to 300 m and wave heights of 2 to 3 m covering an area of 7 k[m.
The dune field is three km long by two km deep and runs from the western edge of the busy beach at Playa del Ingles - the second largest resort in Europe after Benidorm.
At about 5000 BP, probably as a direct result of the monsoon shift, the most hydrologically fragile segments of the area (pediment, playas and dune field lakes) dried out, while the depletion of soil water reserves had been completed, at least locally, by about 3500 BP.
So as Curiosity traverses Gale's dune field it will have a chance to get a good look at these features up close, hopefully giving us our first close-up images of their ponderous shuffle across the crater floor.
The landing site, although surrounded by a vast dune field, reveals a landscape carved almost entirely by three different liquid erosion events - rainfall, flooding and seepage," Griffith (http://www.
The preserve, which is part of the second largest dune field in the continental United States and possibly in all of North America, will be incorporated into the Guadalupe Mountains National Park.
These grindstone quarries are typically located where there are suitable sandstone outcrops on the edge of large tracts of sand plain, dune field or stony 'gibber' desert - areas where sandstone slabs are otherwise scarce.
As the AUV tracked above the bottom at a particularly dynamic area of the reef called Hydrographers Passage, about 200 km off the mainland, a vast sandy dune field supporting an extensive community of the luminescent, suspension feeding brittle stars (relatives of sea stars) came into view for the first time.
As dome dunes migrate into the heart of the dune field, they fuse together in long rows and become stretched by the wind.