The barkhan dune has its etymology in the Russian language of Turkistan. Russian naturalist, Alexander von Middendorf is credited with introducing the word for these crescent-shaped sand dunes into scientific literature in 1881.
Barkhans face the wind and are produced by wind action predominately from one direction. They are very common, crescent or arc-shaped, and are characteristic of sandy deserts all over the world. They are markedly asymmetrical in their cross section with a gentle slope facing toward the wind sand ridge comprised of well-sorted sand.
This type of dune possesses two "horns" that face downwind, with the steeper slope, known as the slip face, on the downwind side, away from the wind. The angle of repose of sand is approximately 30–35 degrees for medium-fine dry sand. The upwind side is packed by the wind and stands at about 15 degrees. Barkhans may be 9–30m (30–100 feet) high and 370m (1,214 feet) wide at the base measured perpendicular to the wind.
Of course, our dune is not presently in a sandy desert. However, you are currently standing on the bottom of a prehistoric ocean which was covered with sand and gravel. It is easy to imagine the blowing sand moving across the area after the glaciers had scraped along the surface and disturbed the soil.
The lee side of the dune, sheltered from the wind and exposed to the morning sun, has become home to a small clump of bushes and trees. In the absence of deforestation, these trees will eventually work their way up the slope and hide the face of the dune. Cultivation has reduced the length of the "horns" somewhat but the essence of the arc is still well-defined.
NOTE: The formation is on private property and should be observed only from the parking area beside the highway. Please do not enter the property in order to answer the questions.
In order to log this cache, please email the cache owner the answers to the following questions:
(Please do not post your answers on the cache page. Cachers who have not sent their answers to the CO will have their logs removed.)
1) What was the direction of the prevailing wind which created this dune?
2) How does the dune develop its horns?
3) Assuming that the dune is a right-angle triangle, and given an approximate 10m height of the face with a 15 degree angle of the upwind-side of an average dune, what is the estimated length of the upwind-side of dune? (The upwind-side of the dune is visible as you approach the cache site from either direction on the highway.)
4) Optional: Please feel free to post a picture of the dune as it is viewed in the various seasons.