What Controls the Shape and Motion of Sand Dunes?
ES1603  Controls on Dune Formation
USGS
Dust storm in Senegal, Africa.
Richard Frear, USGS
Sand Dunes in Death Valley, California.

1. Which of the images shows sediments in motion? What is causing it to move?


Peter Kresan, University of Arizona
Sand dunes in Algodones, California.
USGS
Close-up photograph of desert soil in China.

2. What accounts for the absence of dunes in the image to the right?


Wind Erosion Research Unit, USDA
Dunes accumulating against hay bales in Pratt County, Kansas.
Wind Erosion Research Unit, USDA
Dust blowing over a field in the central plains of North America.

3. Why are dunes forming against the hay bales but not in the open field?


Wind Erosion Research Unit, USDA
Irrigated cropland in the central plains of North America.
Wind Erosion Research Unit, USDA
Sand dunes in the Sahara Desert of Africa.

4. Which of the images was taken in an area with abundant water?

5. Suggest two reasons for the presence of dunes in Image B but not in Image A.


6. From these images, predict the conditions required for dune formation.


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