Geological process of wind group-4 spav 1st year planning

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The School of Planning and Architecture, Vijayawada

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Geological Process of Wind (erosion, transportation and deposition) : 

Geological Process of Wind (erosion, transportation and deposition) GROUP MEMBERS : PARIKSHIT MEHTA RAJIV MENON K DEEPAK KUMAR HANSDAAH GEOLOGY & HYDROLOGY DEPT. OF PLANNING SCHOOL OF PLANNING AND ARCHITECTURE VIJAYAWADA GUIDED BY:- PROF. SARATH BABU

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Some geological 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.

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Although water is a much more powerful eroding force than wind, Aeolian processes are important in arid environments such as deserts.

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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).

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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.

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Deflation basins, called blowouts, are hollows formed by the removal of particles by wind. Blowouts are generally small, but may be up to several kilometres in diameter. Wind-driven grains abrade landforms. Grinding by particles carried in the wind creates grooves or small depressions.

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The velocity of wind increases with height above the surface, hence wind is only able to carry very fine particles such as clay and silt in suspension. Particles .the size of a grain of sand are rolled or skipped along the surface in the wind’s bed load. Particles which are larger than the size of a grain of sand are usually not transported by wind. This lifting up and removal of loose materials by wind is called deflation

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Deflation may be difficult to notice as entire surfaces are being lowered at the same time.

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WIND TRANSPORTATION This process results in the formation of ripples and sand dunes. Typically, the size of the transported sediment is fine sand (<1 mm) and smaller, because air is a fluid with low density and viscosity, and can therefore not exert very much shear on its bed.

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Aeolian sediment transport is common on beaches and in the arid regions of the world, because it is in these environments that vegetation does not prevent the presence and motion of fields of sand. A plume of dust blows off of the Sahara Desert and sails over Atlantic Ocean towards the Canary Islands.

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Very fine material may be carried in suspension in the air - But larger particles may be moved by 2 methods surface creep & saltation

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1.) SURFACE CREEP - material is rolled along the surface - accounts for 20% of wind transport

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2.) SALTATION - The asymmetrical bouncing of sand grains - Accounts for 80% of wind transport - Cause of shifting sand dunes

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WIND 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 moulded it. Wind-deposited sand bodies occur as sand sheets, ripples, and dunes.

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Sand sheets are flat, gently undulating sandy plots of sand surfaced by grains that may be too large for siltation. They form approximately 40 percent of Aeolia depositional surfaces. The Selma Sand Sheet, which occupies 60,000 square kilometre in southern Egypt and northern Sudan, is one of the Earth's largest sand sheets.

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The Selma is absolutely flat in some places; in others, active dunes move over its surface.

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loess: a deposit of wind-blown silt and clay composed of un weathered, angular grains of quartz, feldspar, and other minerals weakly cemented by calcite - have a high porosity, typically near 60% Vertical road cuts in loess Vicksburg, Mississippi

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Sand Dunes sand dunes: mounds of loose sand grains heaped up by the wind, most likely to develop in areas with strong winds that generally blow in the same direction

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sand grains found in dunes are commonly well-sorted and well-rounded because wind is very selective as it moves sediment

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Sand Dunes slip face: the steep downwind slope of a dune wind ripples: small, low ridges of sand produced by saltation of the grains Wind ripples on sand surface - Monument Valley, Utah

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GEOLOGICAL PROCESS CHART

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