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Planetary Geology pdf - NASA

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Gradation<br />

2. Figure 3.4 shows a portion of White Sands, New Mexico, an area affected by aeolian (wind) processes.<br />

The crescent-shaped features are dunes composed of sand. Most sand dunes have a gentle slope on their<br />

windward side and a steeper slope to the leeward side. High velocity winds blow sand up the windward<br />

side to the brink of the dune; sand then slides down the leeward slip face of the dune.<br />

a. Examine the photographs stereoscopically and identify the slip faces on the dunes. From which direction<br />

is the wind blowing?<br />

b. Consider one of the dunes near the center of the photo. Where will its sand go in time?<br />

c. How does the morphology of the sand dunes change across the photo? Use sketches of at least two<br />

dunes to illustrate your answer.<br />

Sketch area<br />

Sketch area<br />

Exercise Three: Geologic Landforms<br />

Seen on Stereoscopic Photos<br />

EG-1998-03-109-HQ Activities in <strong>Planetary</strong> <strong>Geology</strong> for the Physical and Earth Sciences<br />

37

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