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Barchan

February 16, 2024

For the village, see Barchan, Iran. For the military operation, see Barkhane.

A barchan or barkhan dune (from Kazakh бархан [bɑɾˈχɑn]) is a crescent-shaped dune. The term was introduced in 1881 by Russian naturalist Alexander von Middendorf,[1] based on their occurrence in Turkestan and other inland desert regions. Barchans face the wind, appearing convex and are produced by wind action predominantly from one direction. They are a very common landform in sandy deserts all over the world and are arc-shaped, markedly asymmetrical in cross section, with a gentle slope facing toward the wind sand ridge, comprising well-sorted sand.

Typical shape
Barchan in the Namib Desert.

This type of dune possesses two "horns" that face downwind, with the steeper slope known as the slip face, facing away from the wind, downwind, at the angle of repose of the sand in question, approximately 30–35 degrees for medium-fine dry sand.[2][3][4] The upwind side is packed by the wind, and stands at about 15 degrees. Barchans may be 9–30 m (30–98 ft) high and 370 m (1,210 ft) wide at the base measured perpendicular to the wind.

Simple barchan dunes may appear as larger, compound barchan or megabarchan dunes, which can gradually migrate with the wind as a result of erosion on the windward side and deposition on the leeward side, at a rate of migration ranging from about one meter to 100 meters per year. Barchans usually occur as groups of isolated dunes and may form chains that extend across a plain in the direction of the prevailing wind. Barchans and mega-barchans may coalesce into ridges that extend for hundreds of kilometers. Dune collisions[5][6] and changes in wind direction spawn new barchans from the horns of the old ones and govern the size distribution of a given field.[7]

As barchan dunes migrate, smaller dunes outpace larger dunes, catching-up the rear of the larger dune and eventually appear to punch through the large dune to appear on the other side. The process appears superficially similar to waves of light, sound, or water that pass directly through each other, but the detailed mechanism is very different. The dunes emulate soliton behavior, but unlike solitons, which flow through a medium leaving it undisturbed (similar to waves passing through water), the sand particles themselves are moved. When the smaller dune catches up the larger dune, the winds begin to deposit sand on the rear dune while blowing sand off the front dune without replenishing it. Eventually, the rear dune has assumed dimensions similar to the former front dune which has now become a smaller, faster moving dune that pulls away with the wind.[8]

Barchan dunes have been observed on Mars, where the thin atmosphere produces winds strong enough to move sand and dust.[9] Marine barchan dunes appear underwater as sands shift their way across the seabed.[10][11]

See also edit

References edit

  1. ^ "Barchan - sand dune".
  2. ^ Pye, Kenneth; Haim Tsoar (2008). Aeolian Sand and Sand Dunes. Springer. pp. 138. ISBN 9783540859109.
  3. ^ Alvarez, Carlos A.; Franklin, Erick M. (2017-12-18). "Birth of a subaqueous barchan dune". Physical Review E. 96 (6): 062906. arXiv:1712.07162. Bibcode:2017PhRvE..96f2906A. doi:10.1103/PhysRevE.96.062906. PMID 29347350. S2CID 25558699.
  4. ^ Alvarez, Carlos A.; Franklin, Erick M. (2018-10-19). "Role of Transverse Displacements in the Formation of Subaqueous Barchan Dunes". Physical Review Letters. 121 (16): 164503. arXiv:1810.11074. Bibcode:2018PhRvL.121p4503A. doi:10.1103/PhysRevLett.121.164503. PMID 30387641. S2CID 53231618.
  5. ^ Hersen, Pascal; Douady, Stéphane (2005). "Collision of barchan dunes as a mechanism of size regulation". Geophysical Research Letters. 32 (21): L21403. Bibcode:2005GeoRL..3221403H. doi:10.1029/2005GL024179. ISSN 0094-8276.
  6. ^ Assis, W. R.; Franklin, E. M. (2020-09-28). "A Comprehensive Picture for Binary Interactions of Subaqueous Barchans". Geophysical Research Letters. 47 (18). arXiv:2009.12671. Bibcode:2020GeoRL..4789464A. doi:10.1029/2020GL089464. ISSN 0094-8276. S2CID 221970569.
  7. ^ H. Elbelrhiti; P. Claudin & B. Andreotti (2005). "Field evidence for surface-wave-induced instability of sand dunes". Nature. 437 (September 29): 720–723 Abstract. Bibcode:2005Natur.437..720E. doi:10.1038/nature04058. PMID 16193049. S2CID 4411463.
  8. ^ Schwämmle, V. & H.J. Herrmann (2003). "Solitary wave behaviour of sand dunes". Nature. 426 (December 11): 619–620 Abstract. doi:10.1038/426619a. PMID 14668849. S2CID 688445.
  9. ^ See for instance:
  10. ^ Couldrey, Amelia J.; Benson, Thomas; Knaapen, Michiel A.F.; Marten, Kerry V.; Whitehouse, Richard J.S. (30 September 2020). "Morphological evolution of a barchan dune migrating past an offshore wind farm foundation" (PDF). Earth Surface Processes and Landforms. 45 (12): 2884–2896. Bibcode:2020ESPL...45.2884C. doi:10.1002/esp.4937. S2CID 225400184.
  11. ^ Snieckus, Darius (23 October 2020). "Shifting sands: R&D gurus report in on scour of 'marching' seabed dunes". Recharge. from the original on 1 November 2020.

External links edit

 
Wikimedia Commons has media related to Barchan.
  • Dune types—Great Sand Dunes National Park
  • The Bibliography of Aeolian Research

February 16, 2024
barchan, village, iran, military, operation, barkhane, barchan, barkhan, dune, from, kazakh, бархан, bɑɾˈχɑn, crescent, shaped, dune, term, introduced, 1881, russian, naturalist, alexander, middendorf, based, their, occurrence, turkestan, other, inland, desert. For the village see Barchan Iran For the military operation see Barkhane A barchan or barkhan dune from Kazakh barhan bɑɾˈxɑn is a crescent shaped dune The term was introduced in 1881 by Russian naturalist Alexander von Middendorf 1 based on their occurrence in Turkestan and other inland desert regions Barchans face the wind appearing convex and are produced by wind action predominantly from one direction They are a very common landform in sandy deserts all over the world and are arc shaped markedly asymmetrical in cross section with a gentle slope facing toward the wind sand ridge comprising well sorted sand Typical shapeBarchan in the Namib Desert This type of dune possesses two horns that face downwind with the steeper slope known as the slip face facing away from the wind downwind at the angle of repose of the sand in question approximately 30 35 degrees for medium fine dry sand 2 3 4 The upwind side is packed by the wind and stands at about 15 degrees Barchans may be 9 30 m 30 98 ft high and 370 m 1 210 ft wide at the base measured perpendicular to the wind Simple barchan dunes may appear as larger compound barchan or megabarchan dunes which can gradually migrate with the wind as a result of erosion on the windward side and deposition on the leeward side at a rate of migration ranging from about one meter to 100 meters per year Barchans usually occur as groups of isolated dunes and may form chains that extend across a plain in the direction of the prevailing wind Barchans and mega barchans may coalesce into ridges that extend for hundreds of kilometers Dune collisions 5 6 and changes in wind direction spawn new barchans from the horns of the old ones and govern the size distribution of a given field 7 As barchan dunes migrate smaller dunes outpace larger dunes catching up the rear of the larger dune and eventually appear to punch through the large dune to appear on the other side The process appears superficially similar to waves of light sound or water that pass directly through each other but the detailed mechanism is very different The dunes emulate soliton behavior but unlike solitons which flow through a medium leaving it undisturbed similar to waves passing through water the sand particles themselves are moved When the smaller dune catches up the larger dune the winds begin to deposit sand on the rear dune while blowing sand off the front dune without replenishing it Eventually the rear dune has assumed dimensions similar to the former front dune which has now become a smaller faster moving dune that pulls away with the wind 8 Barchan dunes have been observed on Mars where the thin atmosphere produces winds strong enough to move sand and dust 9 Marine barchan dunes appear underwater as sands shift their way across the seabed 10 11 See also editGreat Sand Dunes National Park and Preserve American national park in Colorado United States Sastrugi also known as Zastruga Sharp irregular grooves or ridges formed on a snow surface about snowforms of similar mechanismReferences edit Barchan sand dune Pye Kenneth Haim Tsoar 2008 Aeolian Sand and Sand Dunes Springer pp 138 ISBN 9783540859109 Alvarez Carlos A Franklin Erick M 2017 12 18 Birth of a subaqueous barchan dune Physical Review E 96 6 062906 arXiv 1712 07162 Bibcode 2017PhRvE 96f2906A doi 10 1103 PhysRevE 96 062906 PMID 29347350 S2CID 25558699 Alvarez Carlos A Franklin Erick M 2018 10 19 Role of Transverse Displacements in the Formation of Subaqueous Barchan Dunes Physical Review Letters 121 16 164503 arXiv 1810 11074 Bibcode 2018PhRvL 121p4503A doi 10 1103 PhysRevLett 121 164503 PMID 30387641 S2CID 53231618 Hersen Pascal Douady Stephane 2005 Collision of barchan dunes as a mechanism of size regulation Geophysical Research Letters 32 21 L21403 Bibcode 2005GeoRL 3221403H doi 10 1029 2005GL024179 ISSN 0094 8276 Assis W R Franklin E M 2020 09 28 A Comprehensive Picture for Binary Interactions of Subaqueous Barchans Geophysical Research Letters 47 18 arXiv 2009 12671 Bibcode 2020GeoRL 4789464A doi 10 1029 2020GL089464 ISSN 0094 8276 S2CID 221970569 H Elbelrhiti P Claudin amp B Andreotti 2005 Field evidence for surface wave induced instability of sand dunes Nature 437 September 29 720 723 Abstract Bibcode 2005Natur 437 720E doi 10 1038 nature04058 PMID 16193049 S2CID 4411463 Schwammle V amp H J Herrmann 2003 Solitary wave behaviour of sand dunes Nature 426 December 11 619 620 Abstract doi 10 1038 426619a PMID 14668849 S2CID 688445 See for instance Nemiroff R Bonnell J eds March 3 2008 Sand Dunes Thawing on Mars Astronomy Picture of the Day NASA Nemiroff R Bonnell J eds April 20 2009 Flowing Barchan Sand Dunes on Mars Astronomy Picture of the Day NASA Couldrey Amelia J Benson Thomas Knaapen Michiel A F Marten Kerry V Whitehouse Richard J S 30 September 2020 Morphological evolution of a barchan dune migrating past an offshore wind farm foundation PDF Earth Surface Processes and Landforms 45 12 2884 2896 Bibcode 2020ESPL 45 2884C doi 10 1002 esp 4937 S2CID 225400184 Snieckus Darius 23 October 2020 Shifting sands R amp D gurus report in on scour of marching seabed dunes Recharge Archived from the original on 1 November 2020 External links edit nbsp Wikimedia Commons has media related to Barchan Dune types Great Sand Dunes National Park The Bibliography of Aeolian Research Retrieved from https en wikipedia org w index php title Barchan amp oldid 1176775413, wikipedia, wiki, book, books, library,

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