Lab 6_WindWaterIce - Lab 6: Lab: Water, Wind and Ice Wind -...

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Lab 6: Lab: Water, Wind and Ice Wind - Eolian Processes Wind is an important agent of erosion in many arid and shore regions of the Earth, and geological processes associated with the wind are called eolian (or aeolian) processes. During wind erosion, small particles are picked up by the wind, bounced along the surface, or rolled, and eventually deposited. Transportation by wind tends to sort the grain sizes of the particles, with fine-grained material being carried farther than coarse- grained material. The most obvious wind-deposited features are dunes, common in some desert areas and seashore regions - places where there is an abundance of sand-sized particles and a prevailing (dominant) wind direction. Formation and movement of sand dunes. Source: Earth: An Introduction to Physical Geology , 7 th ed., Tarbuck & Lutgens, 2002 Wind has extensively modified the surface of Mars through both erosion and deposition. In images having the highest resolution from the Mars Global Surveyor, eolian features predominate. Wind direction and dune types If wind acts in one direction for a large part of the year, this direction is known as the prevailing wind direction . By studying the shape of the deposits left by the wind, the prevailing wind direction can be determined. If any obstacles are in the path of the wind, such as boulders, impact craters, or other surface topography, material will tend to be deposited on the downwind or lee side of the obstacle. If there are no significant obstacles, material may be deposited in piles called dunes which themselves form an obstacle to the wind and further enhance deposition. Dunes may form as lines across the wind direction ( transverse dunes), as lines parallel to the wind direction ( longitudinal
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dunes), or as arcuate piles with the arms of the arcs pointing either upwind ( crescent dunes) or downwind ( barchan dunes). Where the dune forms across the wind, its cross section is distinctly asymmetric with a gentle slope pointing upwind, and a steeper slope pointing downwind. If there is no single prevailing wind direction, irregularly or star- shaped dunes may be formed. Sometimes erosional remnants are left by the wind parallel to the wind direction. These remnants may look similar to longitudinal dunes and are called yardangs. Yardangs may be carved from any consolidated or semiconsolidated material. Viewed from above, their shape resembles inverted boat hulls. They are highest and broadest at the end which faces the direction of the incoming wind, and become lower and narrower toward the lee end. Martian Sand Dunes. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) high resolution image shows a field of dark sand dunes on the floor of Kaiser Crater in southeastern Noachis Terra. The steepest slopes on each dune, the slip faces, point toward the east, indicating that the strongest winds that blow across the floor of Kaiser
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Lab 6_WindWaterIce - Lab 6: Lab: Water, Wind and Ice Wind -...

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