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 ?
As the storm moves north, those large waves are expected to erode and in some cases overwash sandy beaches and dunes that serve as protection for coastal communities.
For a moment, I paused to remember the thrill of speeding down a dune.
Luckily, the dunes expand over 30 square miles, and, according to Ranger Myers, 99 percent of the visitors hover around the first three.
Our resort promises an exhilarating experience that our guests are bound to keep reminiscing about," says Niti Ajit Karsandas Hamlai, managing director of Al Nahda Hotels and Resorts the parent company of Dunes by Al Nahda.
Alongside the plans for a second band of sand dunes, other plans to help protect the town and minimise flood risk include replacing timber flood boards between Splash Point and the golf course with steel flood gates, to help direct flood waters from the Garford Road Car Park onto Rhyl Golf Course, as well as other more long term measures at Splash Point.
It feels somehow like a roller coaster, although the thought of the car falling off the dunes doesn't leave your mind.
The first guests were led to Dune Star Camp by expert guide Chantelle Bosch.
However, when the wind at the ocean turns into a breeze off the land, the stored sand can be blown off the dune and back onto the beach.
It's possible that one process plays a more important role than the other in shaping dune swarms, says geomorphologist Christopher Hugenholtz of the University of Calgary in Canada.
The creation of a more unisex environment to reflect the success of the Dune London men's range, which now accounts for 25 per cent of the business in the UK and 15 per cent globally; and providing a designated area for accessories, and day bags in particular, which have seen a growth in sales of over 300 per cent in the last year, truly make this a unique and distinctive destination footwear and accessories store for both men and women.
THOUSANDS of Christmas trees are being used to help prevent the erosion of Merseyside's sand dunes.
Cara's Dune Buggy Dash game follows a simplistic yet addictive format with the user coming back to try and top the high score board.