Aeolian (or Eolian or Æolian) processes pertain to the activity of the winds and more specifically, to the winds' ability to shape the surface of the Earth and other planets. Wind is the flow of Air or other Gases that compose an Atmosphere (including but not limited to the Earth's) EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is Winds may erode, transport, and deposit materials, and are effective agents in regions with sparse vegetation and a large supply of unconsolidated sediments. Vegetation is a general term for the plant life of a region it refers to the Ground cover provided by plants Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of Although water is much more powerful than wind, aeolian processes are important in arid environments such as deserts. A desert is a Landscape or region that receives very little precipitation.
The term is derived from the name of the Greek god, Æolus, the keeper of the winds. For the Click beetle Genus, see Aeolus (beetle. Aeolus ( Greek:, Ailos Modern Greek
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Wind erosion
Wind erodes the Earth's surface by deflation (the removal of loose, fine-grained particles), by the turbulent eddy action of the wind and by abrasion (the wearing down of surfaces by the grinding action and sandblasting of windborne particles). Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind In Fluid dynamics, turbulence or turbulent flow is a fluid regime characterized by chaotic Stochastic property changes In Fluid dynamics, an eddy is the swirling of a Fluid and the reverse current created when the fluid flows past an obstacle Abrasion is mechanical scraping of a rock surface by Friction between rocks and moving particles during their transport in Wind, Glacier, Waves Sandblasting or Bead blasting is a generic term for the process of smoothing shaping and cleaning a hard surface by forcing solid particles across that surface at high speeds
Regions which experience intense and sustained erosion are called deflation zones. Most aeolian deflation zones are composed of desert pavement, a sheet-like surface of rock fragments that remains after wind and water have removed the fine particles. A desert pavement is a Desert surface that is covered with closely packed interlocking angular or rounded rock fragments of pebble and cobble size Almost half of Earth's desert surfaces are stony deflation zones. The rock mantle in desert pavements protects the underlying material from deflation. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided A desert pavement is a Desert surface that is covered with closely packed interlocking angular or rounded rock fragments of pebble and cobble size
A dark, shiny stain, called desert varnish or rock varnish, is often found on the surfaces of some desert rocks that have been exposed at the surface for a long period of time. Desert varnish, or rock varnish is a dark coating found on exposed rock surfaces in Arid environments Manganese, iron oxides, hydroxides, and clay minerals form most varnishes and provide the shine. Manganese (ˈmæŋgəniːz is a Chemical element, designated by the symbol Mn. Altogether there are sixteen known Iron Oxides and oxyhydroxides In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen Clay is a naturally occurring material composed primarily of fine-grained Minerals which show plasticity through a variable range of Water content, and
Deflation basins, called blowouts, are hollows formed by the removal of particles by wind. Blowouts are sandy depressions in a sand Dune ecosystem (psammosere caused by the removal of sediments by Wind. Blowouts are generally small, but may be up to several kilometers in diameter.
Wind-driven grains abrade landforms. Grinding by particles carried in the wind creates grooves or small depressions. Depression in Geology is a Landform sunken or depressed below the surrounding area Ventifacts are rocks which have been cut, and sometimes polished, by the abrasive action of wind. Ventifacts are rocks that have been abraded pitted etched grooved or polished by wind-driven sand
Sculpted landforms, called yardangs, are up to tens of meters high and kilometers long and are forms that have been streamlined by desert winds. A yardang is a wind-abraded ridge found in a desert environment The famous sphinx at Giza in Egypt may be a modified yardang. A Sphinx is a Zoomorphic mythological figure which is depicted as a recumbent lion with a human head You may have been looking for the Great Pyramid of Giza. For the three pyramids of Giza visit the Giza pyramid complex.
Transport
Particles are transported by winds through suspension, saltation, and creep. In Chemistry, A suspension is a Heterogenous fluid containing Solid particles that are sufficiently large for Sedimentation. For definition and other use disambiguation see Saltation In Geology, saltation (from Latin, saltus, "leap" Downhill creep, or commonly just creep, is the slow downward progression of rock and Soil down a low grade slope it can also refer to slow deformation
Small particles may be held in the atmosphere in suspension. An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere " Upward currents of air support the weight of suspended particles and hold them indefinitely in the surrounding air. Typical winds near Earth's surface suspend particles less than 0. 2 millimeters in diameter and scatter them aloft as dust or haze. Dust is a general name for minute Solid particles with Diameters less than 500 micrometers. Haze is traditionally an atmospheric phenomenon where dust smoke and other dry particles obscure the clarity of the sky
Saltation is downwind movement of particles in a series of jumps or skips. For definition and other use disambiguation see Saltation In Geology, saltation (from Latin, saltus, "leap" Saltation normally lifts sand-size particles no more than one centimeter above the ground, and proceeds at one-half to one-third the speed of the wind. A saltating grain may hit other grains that jump up to continue the saltation. The grain may also hit larger grains that are too heavy to hop, but that slowly creep forward as they are pushed by saltating grains. Surface creep accounts for as much as 25 percent of grain movement in a desert.
Aeolian turbidity currents are better known as dust storms. A turbidity current or density current is a current of rapidly moving sediment-laden water moving down a slope through air water or another fluid Air over deserts is cooled significantly when rain passes through it. This cooler and denser air sinks toward the desert surface. When it reaches the ground, the air is deflected forward and sweeps up surface debris in its turbulence as a dust storm. Debris (ˈdeɪbriː/ /dɛˈbriː is a word used to describe the remains of something that has been otherwise destroyed
Crops, people, villages, and possibly even climates are affected by dust storms. A village is a clustered human settlement or community, larger than a hamlet, but smaller than a Town or City. Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of Some dust storms are intercontinental, a few may circle the globe, and occasionally they may engulf entire planets. A globe is a three- Dimensional scale model of Earth ( terrestrial globe) or other spheroid celestial body such as a planet star or moon When the Mariner 9 spacecraft entered its orbit around Mars in 1971, a dust storm lasting one month covered the entire planet, thus delaying the task of photo-mapping the planet's surface. Mariner 9 (Mariner Mars '71 / Mariner-I was a NASA space probe orbiter that helped in the exploration of Mars and was part of the Mariner program.
Most of the dust carried by dust storms is in the form of silt-size particles. Silt is Soil or rock derived Granular material of a Grain size between sand and clay Deposits of this windblown silt are known as loess. Loess is a homogeneous typically non stratified porous Friable,slightly coherent often calcareous fine-grained Silty pale yellow or buff windblown ( aeolian The thickest known deposit of loess, 335 meters, is on the Loess Plateau in China. The Loess Plateau ( also known as the Huangtu Plateau is a Plateau that covers an area of some 640000 km² in the upper and middle of China 's China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National In Europe and in the Americas, accumulations of loess are generally from 20 to 30 meters thick. The Americas are the lands of the Western hemisphere or New World, consisting of the Continents of North America and South America
Small whirlwinds, called dust devils, are common in arid lands and are thought to be related to very intense local heating of the air that results in instabilities of the air mass. A dust devil is a strong well-formed and relatively long-lived whirlwind, ranging from small (half a meter wide and a few meters tall to large (over 10 meters wide and over Dust devils may be as much as one kilometer high.
Deposition
Wind-deposited materials hold clues to past as well as to present wind directions and intensities. These features help us understand the present climate and the forces that molded it. Wind-deposited sand bodies occur as sand sheets, ripples, and dunes. In physical Geography, a dune is a Hill of Sand built by Aeolian processes.
Sand sheets are flat, gently undulating sandy plots of sand surfaced by grains that may be too large for saltation. They form approximately 40 percent of aeolian depositional surfaces. The Selima Sand Sheet, which occupies 60,000 square kilometers in southern Egypt and northern Sudan, is one of the Earth's largest sand sheets. This article is about the country of Egypt For a topic outline on this subject see List of basic Egypt topics. Sudan (officially the Republic of Sudan) ( السودان al-Sūdān is a country in northeastern Africa. The Selima is absolutely flat in some places; in others, active dunes move over its surface. In physical Geography, a dune is a Hill of Sand built by Aeolian processes.
Wind blowing on a sand surface ripples the surface into crests and troughs whose long axes are perpendicular to the wind direction. A capillary wave is a Wave travelling along the interface between two fluids whose dynamics are dominated by the effects of Surface tension. A crest is the point on a Wave with the greatest positive value or upward displacement in a Cycle. In Geometry, two lines or planes (or a line and a plane are considered perpendicular (or orthogonal) to each other if they form congruent The average length of jumps during saltation corresponds to the wavelength, or distance between adjacent crests, of the ripples. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. In ripples, the coarsest materials collect at the crests. This distinguishes small ripples from dunes, where the coarsest materials are generally in the troughs.
Wind-blown sand moves up the gentle upwind side of the dune by saltation or creep. Sand accumulates at the brink, the top of the slipface. When the buildup of sand at the brink exceeds the angle of repose, a small avalanche of grains slides down the slipface. This article refers to the natural event For other uses see Avalanche (disambiguation An avalanche is an abrupt and rapid flow of snow often Grain by grain, the dune moves downwind.
Accumulations of sediment blown by the wind into a mound or ridge, dunes have gentle upwind slopes on the wind-facing side. A mound is a general term for an artificial heaped Pile of Earth, Gravel, Sand, rocks A ridge is a geological feature that features a continuous elevational crest for some distance The downwind portion of the dune, the lee slope, is commonly a steep avalanche slope referred to as a slipface. Dunes may have more than one slipface. The minimum height of a slipface is about 30 centimeters.
Some of the most significant experimental measurements on aeolian sand movement were performed by Ralph Alger Bagnold, a British engineer who worked in Egypt prior to World War II. Ralph Alger Bagnold, FRS ( April 3 1896 &ndash May 28 1990) was the founder and first commander of the British Army 's This article is about the country of Egypt For a topic outline on this subject see List of basic Egypt topics. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including Bagnold investigated the physics of particles moving through the atmosphere and deposited by wind. He recognized two basic dune types, the crescentic dune, which he called "barchan," and the linear dune, which he called longitudinal or "sief" (Arabic for "sword"). A barchan Dune is an arc-shaped sand ridge comprising well-sorted sand
See also
References
- Eolian Processes (HTML). In Geology, cross-bedding refers to inclined sedimentary structures in a horizontal unit of rock WEELS ("Wind Erosion on European Light Soils" was a research project funded as part of the EU Environment and Climate Programme, intended to develop a small-scale USGS (1997). Retrieved on 2006-11-01. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 996 - Emperor Otto III issues a deed to Gottschalk Bishop of Freising which is the oldest known document using the name Ostarrîchi
External links
- The Bibliography of Aeolian Research
- Facts about wind erosion and dust storms on the Great Plains hosted by the UNT Government Documents Department
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