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Eolian (or aeolian 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. Winds may erode, transport, and deposit materials, and are effective agents in regions with sparse vegetation and a large supply of unconsolidated sediments. Although water is much more powerful than wind, æolian processes are important in arid environments such as deserts. Wind, tacuinum sanitatis casanatensis (XIV century) Given a difference in barometric pressure between two air masses, a wind will arise between the two which tends to flow from the area of high pressure to the area of low pressure until the two air masses are at the same pressure, although...
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 water or other liquid. ...
This article is about arid terrain. ...
The term is derived from the name of the Greek god, Æolus, the keeper of the winds. This article or section does not cite its references or sources. ...
Wind Erosion Wind erodes the Earth's surface by deflation, by 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 sand blasting of windborne particles). Image File history File links Size of this preview: 398 × 600 pixel Image in higher resolution (900 × 1356 pixel, file size: 842 KB, MIME type: image/jpeg) Monument showing effects of wind erosion Image ID: theb1564, Historic C&GS Collection Credit: NOAA National Geodetic Survey Source: [1] File history Legend...
Image File history File links Size of this preview: 398 × 600 pixel Image in higher resolution (900 × 1356 pixel, file size: 842 KB, MIME type: image/jpeg) Monument showing effects of wind erosion Image ID: theb1564, Historic C&GS Collection Credit: NOAA National Geodetic Survey Source: [1] File history Legend...
The National Geodetic Survey is the successor agency in the United States to the U.S. Coast and Geodetic Survey. ...
Survey markers, or survey monuments, are objects placed to mark key survey points on the earths surface. ...
Severe soil erosion in a wheat field near Washington State University, USA. For erosion as understood by materials science, see Erosion (materials science) For erosion as an English analogy, see Erosion (figurative) For erosion as an operation of Mathematical morphology, see Erosion (morphology) Erosion is the displacement of solids (soil...
In fluid dynamics, turbulence or turbulent flow is a flow 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. ...
Glacially abraded rocks in western Norway near Jostedalsbreen glacier. ...
Sandblasting 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. ...
Most æolian 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. Almost half of Earth's desert surfaces are stony deflation zones. The rock mantle in desert pavements protects the underlying material from deflation. 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. Manganese, iron oxides, hydroxides, and clay minerals form most varnishes and provide the shine. General Name, Symbol, Number manganese, Mn, 25 Chemical series transition metals Group, Period, Block 7, 4, d Appearance silvery metallic Atomic mass 54. ...
Iron oxide pigment There are a number of iron oxides: Iron oxides Iron(II) oxide or ferrous oxide (FeO) The black-coloured powder in particular can cause explosions as it readily ignites. ...
Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: OH− It has a charge of −1. ...
The Gay Head cliffs in Marthas Vineyard are made almost entirely of clay. ...
Deflation basins, called blowouts, are hollows formed by the removal of particles by wind. Blowouts are generally small, but may be up to several kilometers in diameter. Blowouts are sandy depressions caused by removal of material by wind. ...
Wind-driven grains abrade landforms. Grinding by particles carried in the wind creates grooves or small depressions. Ventifacts are rocks which have been cut, and sometimes polished, by the abrasive action of wind. Ventifact at Ventifact Ridge in Death Valley Ventifacts are rocks that have been abraded, 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. The famous sphinx at Giza in Egypt may be a modified yardang. A yardang near Meadow, Texas (USDA photo by J.E. Stout). ...
The Great Sphinx of Giza, with the Pyramid of Khafre in the background For other uses, see Sphinx (disambiguation). ...
Pyramids of Giza in 1960s Egypt: Site of Giza or Al Jizah (top center). ...
Transport Particles are transported by winds through suspension, saltation, and creep. Flour suspended in water In chemistry, a suspension is a colloidal dispersion (mixture) in which a finely-divided species is combined with another species, with the former being so finely divided and mixed that it doesnt rapidly settle out. ...
In geology, saltation (from Latin, saltus, leap) refers to a bouncing-like motion when alluvium is dislodged from the streambed, travels in a parabolic path through the stream water, and then impacts back on to the bed. ...
The slow prgoression of rock and other debris down a low grade slope; it can also refer to slow deformation of such materials as a result of prolonged pressure and stress. ...
Small particles may be held in the atmosphere in suspension. 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.
Saltation is downwind movement of particles in a series of jumps or skips. 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.
Æolian turbidity currents are better known as dust storms. 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. A sandstorm approaching Al Asad, Iraq, just before nightfall on April 27 2005. ...
Crops, people, villages, and possibly even climates are affected by dust storms. Some dust storms are intercontinental, a few may circle the globe, and occasionally they may engulf entire planets. When the Mariner 9 spacecraft arrived at Mars in 1971, the entire planet was enshrouded in global dust. Mariner 9 launch Mariner 9 was a NASA space probe orbiter that helped in the exploration of Mars and was part of the Mariner program. ...
Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ...
Most of the dust carried by dust storms is in the form of silt-size particles. Deposits of this windblown silt are known as loess. The thickest known deposit of loess, 335 meters, is on the Loess Plateau in China. In Europe and in the Americas, accumulations of loess are generally from 20 to 30 meters thick. Silt is soil or rock derived granular material of a specific grain size. ...
This article or section does not cite its references or sources. ...
The Loess Plateau is a plateau that covers an area of some 640,000 km² in the upper and middle parts of Chinas Yellow River. ...
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. Dust devils may be as much as one kilometer high. A dust devil in the Mojave Desert. ...
Deposition
 The edge of a slipface on a sand dune in Death Valley National Park 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. Image File history File links Size of this preview: 450 × 600 pixel Image in higher resolution (768 × 1024 pixel, file size: 106 KB, MIME type: image/jpeg) The edge of a slipface on a sand dune in Death Valley National Park. ...
Image File history File links Size of this preview: 450 × 600 pixel Image in higher resolution (768 × 1024 pixel, file size: 106 KB, MIME type: image/jpeg) The edge of a slipface on a sand dune in Death Valley National Park. ...
Death Valley and Panamint Range The salt lake at Badwater, Death Valley is the lowest point in western hemisphere. ...
For the Frank Herbert novel, see Dune (novel) Mesquite Flat Dunes in Death Valley National Park In physical geography, a dune is a hill of sand built by eolian 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 eolian 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. The Selima is absolutely flat in some places; in others, active dunes move over its surface.
Wind blowing on a sand surface ripples the surface into crests and troughs whose long axes are perpendicular to the wind direction. The average length of jumps during saltation corresponds to the wavelength, or distance between adjacent crests, of the ripples. 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. 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. 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 eolian sand movement were performed by Ralph Bagnold, a British engineer who worked in Egypt prior to World War II. 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"). Ralph A. Bagnold (April 3, 1896 - May 28, 1990), during World War II, was the founder and first commander of the British Armys Long Range Desert Group. ...
A barchan dune is an arc-shaped sand ridge, comprised of well-sorted sand. ...
See also Cross bedding is a geological term referring to the way a sedimentary deposit is affected by water currents, during its formation. ...
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 model of wind erosion at the level of individual farms and fields, based on research at three test sites in Lower Saxony, Skania...
References For the Manfred Mann album, see 2006 (album). ...
November 1 is the 305th day of the year (306th in leap years) in the Gregorian Calendar, with 60 days remaining. ...
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