Dunes


Also found in: Dictionary, Thesaurus, Medical, Legal, Wikipedia.

Dunes

 

sand reliefs formed by the wind.

Usually the term “dunes” is applied to all sand build-ups regardless of zonal and climatic conditions; in the USSR the term refers only to forms of nondesert sand relief: on the shores of seas and lakes, on river terraces, in morainic aprons, and so forth. In contrast to the barchans developed in deserts, dunes (in this sense) have a convex form on the steep side, not on the sloping side, and the “tails” are located behind the dunes, on the windward side. The sloping side faces upwind and has an angle of inclination of 8°-20°; the downwind side approaches the angle of repose of dry (32°-33°) or moist sand (up to 40°). Dunes range from 5 to 30 m high and more [on the Courland Spit in the Baltic Sea (in Lithuania) a dune 58 m high is known; in Les Landes, on the coast of the Bay of Biscay (in France) there is one 97 m high]. Dunes may shift in the direction of the prevailing wind at a speed of 10 m a year, depending on the weight of the sand and the wind velocity.

The evolution of nondesert dunes, with a prevailing wind direction, is expressed in the gradual transition from coastal or riverside dune banks, which as a rule are transverse to the wind, into staple-shaped, parabolic, and hairpin-shaped forms. Under seasonal winds directed at angles of less than 90°, spear-shaped dunes form. In areas with convective or interfering wind patterns, rounded, ridge-like dunes develop, with a scattering from the center toward the periphery. Moreover, with time simple shapes turn into complex ones. The movement of denuded dunes, which cause great harm to the economy, is being combatted by the planting of wooded vegetation (mostly pines).

B. A. FEDOROVICH

References in periodicals archive ?
Tim Parker, President of Northwest Green Products, said, "Bandon Dunes is a jewel in our community.
Even if they disagree, "both papers are providing convincing evidence that the generation of small dunes in a field is a very important ingredient to explain the structure of barchan corridors," says Eric Parteli of the University of Erlangen-Nuremberg in Germany.
But in the 1950s the local rabbit population was decimated by the myxomytosis epidemic, allowing vegetation to get the upper hand on the dunes.
The scientists, who worked in the remote Tengger desert of Inner Mongolia, used a bulldozer to flatten 160,000 square metres of sand dunes in 2008 and over the next three-and-a-half years, they watched the dunes rebuild by closely tracking the winds.
Andrew Brockbank, countryside manager for the National Trust at Formby, said: "Our dunes are moving inland as the coastline retreats at a rate of around four metres a year.
The Countryside Council for Wales (CCW) aims to create small, new areas of bare, open sand and dune slacks, which will boost the survival chances of some of the sand dunes' rarest plants and insects - including petalwort, sand wasps, mining bees and rare beetles.
Outside the boundaries of the parks, two of the major threats to the plant are the alteration of the natural flow of sand along the shoreline and the destruction of dunes caused by real estate development.
sanctaerosae encountered on the dunes on calm, warm evenings (Mar.
Carter's basic design changes from sand dunes to battlefield trenches and back again with splendid lighting, while French's costumes contribute important atmospheric details.
The Dunes VS-O Lifecycle and VS-O Desktop applications enable SMEs to automate and access two critical data center services so that they can free up IT staff to perform more critical tasks," said John Humphreys, vice president, Enterprise Virtualization Software at IDC.