| Dunes - Reversing Dunes | |||
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Reversing dunes are dune ridges that form perpendicular to the wind direction. The location of the active slip face changes sides (reverses) on the dune when the wind changes direction. Reversing dunes commonly possess major and minor slip faces that are oriented in opposite directions. Most reversing dunes occur in fields of crescentic dune mounds or ridges. Reversing dunes occur in deserts with bimodal wind patterns. Large collections of reversing dunes are found in Great Sand Dunes National Park, Colorado, and the desert areas of California. Other reversing dunes are found in western Africa, the Arabian Peninsula and the Gobi Desert (China). |
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Winds and Dune Formation A bimodal wind regime is a pattern of winds from two directions that are nearly opposite each other. In some places, the winds change direction seasonally. Dune ridges form as the wind blows from one direction during much of the year. The slip face forms on the downwind, or lee side, of the dune. When the wind reverses, the dune changes to form a slip face on the opposite side (downwind from the new wind direction). Reversing dunes tend to grow taller rather than moving forward across the landscape. |
 Bimodal wind patterns in Great Sand Dunes National Park. Prevailing winds are from the southwest, but opposite winds can emerge from the mountain passes. (Source: Great Sand Dunes National Park) |
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Last
updated 03/23/10.