Issaouane Erg, Algeria. Both star and crescentic dunes can be seen in this orbital photo.

An erg (also sand sea or dune sea) is a large, relatively flat area of desert covered with wind-swept sand with little to no vegetation cover.^[1] The term takes its name from the Arabic word erg ( عرج), meaning "dune field".^[2] Strictly speaking, an erg is defined to be a desert area that contains more than 125 square kilometers of eolian sand^[3] and where sand covers more than 20% of the surface.^[2] Smaller areas are known as dune fields. The largest hot desert in the world, the Sahara, is 9,000,000km² and contains several ergs, such as Erg Chech in Algeria.^[4] Approximately 85% of all the Earth's mobile sand is found in ergs that are larger than 32,000 km².^[3] Image File history File links Size of this preview: 800 × 530 pixelsFull resolution (1000 × 662 pixel, file size: 491 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Erg (landform) ... Image File history File links Size of this preview: 800 × 530 pixelsFull resolution (1000 × 662 pixel, file size: 491 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Erg (landform) ... This article is about arid terrain. ... This article or section does not cite any references or sources. ... Patterns in the sand Sand is a granular material made up of fine rock particles. ... Arabic ( or just ) is the largest living member of the Semitic language family in terms of speakers. ... Square kilometre (US spelling: Square kilometer), symbol km², is an SI unit of surface area. ... Eolian (or aeolian) processes pertain to the activity of the winds. ... For the Frank Herbert novel, see Dune (novel) A diagram showing the formation of a dune with a slipface. ...

Description

Ergs are concentrated in two broad belts between 20° to 40° N and 20° to 40° S latitudes, which include regions crossed by the dry, subsiding air of the trade winds. Active ergs are limited to regions that receive, on the average, no more than 150 mm of annual precipitation.^[2] The largest are in northern and southern Africa, central and western Asia, and Central Australia. In South America, they are areally limited by the Andes Mountains, but they contain extremely large dunes in coastal Peru and northwestern Argentina. The only active erg in North America is in the Gran Desierto de Altar portion of the Sonoran Desert in northwestern Sonora, Mexico, which extends northward into the Yuma Desert of Arizona and the Algodones Dunes of southeastern California. An erg that has been fixed by vegetation forms the Nebraska Sand Hills. The trade winds are a pattern of wind that are found in bands around the Earths equatorial region. ...  Northern Africa (UN subregion)  geographic North Africa, including the UN subregion North Africa or Northern Africa is the northernmost region of the African continent, generally divided politically from Sub-Saharan Africa. ... Categories: Africa geography stubs | Southern Africa ... A world map showing the continent of Africa Africa is the worlds second-largest and second most-populous continent, after Asia. ... Map of Central Asia showing three sets of possible boundaries for the region Central Asia located as a region of the world Central Asia is a vast landlocked region of Asia. ... This article does not adequately cite its references or sources. ... World map showing the location of Asia. ... Central Australia is a term used to describe the area of land surrounding and including Alice Springs in Australia. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... Planes view of the Andes, Peru. ... World map showing North America A satellite composite image of North America. ... The Gran Desierto de Altar is one of the major portions of the Sonoran Desert of Mexico, including the only active erg dune region in North America. ... Map of the Mojave and Sonoran deserts. ... This article is about the Mexican state of Sonora. ... The Yuma Desert is a lower-elevation section of the Sonoran Desert in the southwestern United States and the northwest of Mexico. ... Official language(s) English Capital Phoenix Largest city Phoenix Area  Ranked 6th  - Total 113,998 sq mi (295,254 km²)  - Width 310 miles (500 km)  - Length 400 miles (645 km)  - % water 0. ... Algodones Dunes The Algodones Dunes are located southeast of the Salton Sea in southern California at the border with Arizona and Baja California, Mexico. ... Official language(s) English Capital Sacramento Largest city Los Angeles Area  Ranked 3rd  - Total 158,302 sq mi (410,000 km²)  - Width 250 miles (400 km)  - Length 770 miles (1,240 km)  - % water 4. ... This article or section does not cite any references or sources. ...

Sand seas and dune fields generally occur in regions downwind of copious sources of dry, loose sand, such as dry riverbeds and deltas, floodplains, glacial outwash plains, dry lakes, and beaches. Almost all major ergs are located downwind from river beds in areas that are too dry to support extensive vegetative cover and are thus subject to long-continued wind erosion. Sand from these abundant sources migrates downwind and builds up into very large dunes where its movement is halted or slowed by topographic barriers to windflow or by convergence of windflow. Entire ergs and dune fields tend to migrate downwind as far as hundreds of kilometers from their sources of sand. Such accumulation requires long periods of time. At least 1 million years are required to build ergs with very large dunes, such as those on the Arabian Peninsula, in North Africa, and in central Asia.^[5] Sand seas that have accumulated in subsiding structural and topographic basins, such as the Murzuk Sand Sea of Libya, may attain great thicknesses (more than 1000 m^[6]) but others, such as the ergs of linear dunes in the Simpson and Great Sandy Deserts of Australia, may be no thicker than the individual dunes superposed on the alluvial plain. Within sand seas in a given area, the dunes tend to be of a single type. For example, there are ergs or fields of linear dunes, of crescentic dunes, of star dunes, and of parabolic dunes, and these dune arrays tend to have consistent orientations and sizes.^[7][8] Riverbed Technology, Inc. ... Nile River delta, as seen from Earth orbit. ... This picture shows the flood plain following a 1 in 10 year flood on the Isle of Wight. ... In geology, a sandur is a phenomenon found mostly in Iceland. ... A man-made lake in Keukenhof, Netherlands A lake is a body of water or other liquid of considerable size contained on a body of land. ... The Beach in Calella, Spain. ... Topography, a term in geography, has come to refer to the lay of the land, or the physiogeographic characteristics of land in terms of elevation, slope, and orientation. ... The Arabian Peninsula Emirets towers in United Arab Emirates; the eastern part of Arabian Penisula The Arabian Peninsula (in Arabic: شبه الجزيرة العربية, or جزيرة العرب) is a peninsula in Southwest Asia at the junction of Africa and Asia consisting mainly of desert. ... Ted Colsons expedition across the Simpson Desert in 1936 The Simpson Desert is a desert covering approximately 170,000 square kilometres[1] in central Australia, occupying an area bounded on the west by the Finke River and the Mabel Range, the Adam Range to the north, the Georgina River... Location of deserts in Australia This article is about the Australian desert. ... An alluvial plain is a relatively flat and gently sloping landform found at the base of a range of hills. ...

By nature, ergs are very active. Smaller dunes form and migrate along the flanks of the larger dunes and sand ridges. Occasional precipitation fills basins formed by the dunes; as the water evaporates, salt deposits are left behind. For other uses, see Salt (disambiguation). ...

Individual dunes in ergs typically have widths, lengths, or both dimensions greater than 500 m.^[2] Both the regional extent of their sand cover and the complexity and great size of their dunes distinguish ergs from dune fields.

Extraterrestrial ergs

See also: List of extraterrestrial dune fields

Ergs are a geological feature that can be found on planets where an atmosphere capable of significant wind erosion acts on the surface for a significant period of time, creating sand and allowing it to accumulate. Today at least three bodies, apart from Earth, are known in the solar system to feature ergs on their surface: Venus, Mars and Titan. This is a list of dune fields not on Earth which have been given official names by the International Astronomical Union. ... The eight planets and three dwarf planets of the Solar System. ... View of Jupiters active atmosphere, including the Great Red Spot. ... Eolian (or aeolian) processes pertain to the activity of the winds. ... Patterns in the sand Sand is a granular material made up of fine rock particles. ... Major features of the Solar System (not to scale; from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth and its Moon, and Mars. ...

Venus

Three dune fields have been recognized by the Magellan probe on Venus.^[9] These seem to be mostly transverse dune fields (with dune crests perpendicular to prevailing winds). Magellan spacecraft at Kennedy Space Center The Magellan spacecraft carried out a mission from 1989-1994, orbiting Venus from 1990-1994. ... Adjectives: Venusian or (rarely) Cytherean Atmosphere Surface pressure: 9. ...

Mars

Mars shows very large ergs, especially next to the polar caps, where dunes can reach a considerable size.^[10] Ergs on Mars can exhibit strange shapes and patterns, due to complex interaction with the underlying surface and wind direction. Adjectives: Martian Atmosphere Surface pressure: 0. ...

Titan

Radar images captured by the Cassini spacecraft as it flew by Titan in October 2005 show sand dunes at Titan's equator much like those in deserts of Earth.^[11] The sand dunes are believed to be formed by wind generated as a result of tidal forces from Saturn on Titan's atmosphere. Cassini-Huygens is a joint NASA/ESA/ASI unmanned space mission intended to study Saturn and its moons. ... Titan (, from Ancient Greek Τῑτάν) or Saturn VI is the largest moon of Saturn and the second largest moon in the solar system,[4] after Jupiters moon Ganymede. ...

The images are evidence that these dunes were built from winds that blow in one direction before switching to another and then back to the first direction and so on, causing the sand dunes to build up in long parallel lines. These tidal winds combined with Titan's west-to-east zonal winds create dunes aligned west-to-east nearly everywhere except close to mountains, which alter wind direction.

The sand on Titan might have formed when liquid methane rained and eroded the ice bedrock, possibly in the form of flash floods. Alternatively, the sand could also have come from organic solids produced by photochemical reactions in Titan's atmosphere.^[12]

List of ergs

Erg Chebbi, Morocco

Image File history File links Download high-resolution version (2000x3008, 1963 KB) Version edited by Buchling File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Desert Wikipedia:Featured pictures Erg (landform) Erg Chebbi Wikipedia:Featured pictures/Places/Landscapes Wikipedia... Image File history File links Download high-resolution version (2000x3008, 1963 KB) Version edited by Buchling File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Desert Wikipedia:Featured pictures Erg (landform) Erg Chebbi Wikipedia:Featured pictures/Places/Landscapes Wikipedia... Erg Chebbi Erg Chebbi (Arabic: ‎) is the sole Saharan erg in Morocco. ... Grand Erg Occidental (centre), as seen from space. ... The Kalahari Desert is a large arid to semi-arid sandy area in southern Kgalagadi Africa extending 900,000 km² (562,500 sq. ... The Negev (נגב, Standard Hebrew Négev / Nágev, Tiberian Hebrew Néḡeḇ / Nāḡeḇ; Arabic النقب an-Naqab) is the desert region of southern Israel. ... Erg Chebbi Erg Chebbi (Arabic: ‎) is the sole Saharan erg in Morocco. ... Dune 7, one of the highest sand dunes in the world (ca. ... Map of the Ténéré The Ténéré is a desert region in the south central Sahara. ... Dust storm in Taklamakan from space, June 25, 2005 The Taklamakan (also Taklimakan) is a desert of Central Asia, in the Xinjiang Uighur Autonomous Region of the Peoples Republic of China. ... For the county in Shanxi province, see Xinjiang County. ... Dzungaria (also Jungaria, Sungaria, Zungaria; Mongolian: Зүүнгар Züüngar, Chinese: 準噶爾, Russian: Džungarija) is a geographical region covering approximately 777,000 km², within the Xinjiang Uygur Autonomous Region, northwestern China. ... For the county in Shanxi province, see Xinjiang County. ... The Tengger desert (腾格里沙漠) covers about 36,700 square km and is in the Gansu Province in China. ... Ningxia (Simplified Chinese: 宁夏; Traditional Chinese: 寧夏; Pinyin: Níngxià; Wade-Giles: Ning-hsia; Postal Pinyin: Ningsia), full name Ningxia Hui Autonomous Region (Simplified Chinese: 宁夏回族自治区; Traditional Chinese: 寧夏回族自治區; Pinyin: Níngxià Huízú ZìzhìqÅ«), is a Hui autonomous region of the Peoples Republic of China, located on the northwest Loess... Ordos Desert 1912 The Ordos Desert (Chinese: 鄂尔多斯沙漠; Pinyin: ÈěrduōsÄ« Shāmò) is a desert and steppe region lying on a plateau in the south of the Inner Mongolian Autonomous Region of the Peoples Republic of China. ... Inner Mongolia (Mongolian: ᠥᠪᠦᠷ ᠮᠣᠨᠺᠤᠯᠤᠨ ᠥᠪᠡᠷᠲᠡᠺᠡᠨ ᠵᠠᠰᠠᠬᠤ ᠣᠷᠤᠨ r Mongghul-un bertegen Jasaqu Orun; Chinese: 内蒙古自治区; Hanyu Pinyin: N... As seen from space Dasht-e Lut is a large salt desert in southeastern Iran. ... The Kyzyl Kum (Uzbek: red sand; also called Qyzylqum) is a desert in Kazakhstan and Uzbekistan. ... A NASA satellite image of the Thar Desert, with the India-Pakistan border superimposed is found in canada, united states. ... The Rub al Khali (الربع الخالي), or Empty Quarter, is the largest sand desert in the world, encompassing the southern third of the Arabian Peninsula, including southern Saudi Arabia, and areas of Oman, the United Arab Emirates and Yemen. ... Satellite view of Al-Dahna desert. ... The Nefud or An-Nafud is a desert area in the northern part of the Arabian peninsula, occupying a great oval depression; 180 mi (290 km) long and 140 mi (225 km) wide. ... The Karakum Desert, also spelled Kara-Kum and Gara Gum (“Black Sand”) (Turkmen: Garagum, Russian: Каракумы) is a desert in Central Asia. ... For the ideology of uniting Ural Altaic peoples, see Turanism. ... A four wheel drive in the Gibson Desert The Gibson Desert is a Western Australian desert made up of sandhills and dry grass. ... Location of deserts in Australia This article is about the Australian desert. ... The Great Victoria Desert is a barren, arid and sparsely populated desert ecoregion in southern Australia. ... Ted Colsons expedition across the Simpson Desert in 1936 The Simpson Desert is a desert covering approximately 170,000 square kilometres[1] in central Australia, occupying an area bounded on the west by the Finke River and the Mabel Range, the Adam Range to the north, the Georgina River... Map of the Mojave and Sonoran deserts. ... This article belongs in one or more categories. ... The Jurassic Period is a major unit of the geologic timescale that extends from about 199. ... Red sandstone interior of Lower Antelope Canyon, Arizona, worn smooth due to erosion by flash flooding over millions of years Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock grains. ... This article or section does not cite any references or sources. ... Official language(s) English Capital Lincoln Largest city Omaha Largest metro area Omaha Area  Ranked 16th  - Total 77,421 sq mi (200,520 km²)  - Width 210 miles (340 km)  - Length 430 miles (690 km)  - % water 0. ... The Yuma Desert is a lower-elevation section of the Sonoran Desert in the southwestern United States and the northwest of Mexico. ... Official language(s) English Capital Phoenix Largest city Phoenix Area  Ranked 6th  - Total 113,998 sq mi (295,254 km²)  - Width 310 miles (500 km)  - Length 400 miles (645 km)  - % water 0. ... Algodones Dunes The Algodones Dunes are located southeast of the Salton Sea in southern California at the border with Arizona and Baja California, Mexico. ... Official language(s) English Capital Sacramento Largest city Los Angeles Area  Ranked 3rd  - Total 158,302 sq mi (410,000 km²)  - Width 250 miles (400 km)  - Length 770 miles (1,240 km)  - % water 4. ... Atacama Desert The Atacama Desert of Chile and Peru is a virtually rainless plateau made up of salt basins (salares), sand, and lava flows, extending from the Andes mountains to the Pacific Ocean. ...

References

NASA Earth Observatory is an online publication of NASA where the public can access satellite imagery and scientific information about our planet for free. ... For the Manfred Mann album, see 2006 (album). ... May 18 is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... The USACE gold castle insignia, worn by officers of the Corps The United States Army Corps of Engineers, or USACE, is made up of some 34,600 civilian and 650 military men and women. ... For the Manfred Mann album, see 2006 (album). ... May 18 is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... Everything2, or E2 for short, is a collaborative Web-based community consisting of a database of interlinked user-submitted written material. ... For the Manfred Mann album, see 2006 (album). ... May 18 is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... NASAs Goddard Space Flight Center (GSFC), located in Greenbelt, Maryland, is a major space science laboratory. ... For the Manfred Mann album, see 2006 (album). ... May 18 is the 138th day of the year (139th in leap years) in the Gregorian calendar. ...

External links

• The Bibliography of Aeolian Research