Aeolian forms of relief: what is the Barkhan dune?


Aeolian forms: What is Barkhan’s dune?

Barkhan dunes are crescent-shaped dunes created by the action of the wind and are common in sandy deserts in many parts of the world. The term Barkhan or Barchans was introduced by the Russian biologist Alexander von Middendorf in 1881 in relation to crescent-shaped dunes in Turkestan and other desert regions. Barkhans are crescent-shaped and are created by the action of wind from one direction. Barkhane can also be found on larger rocks and bushes that act as anchors that hold the central area in place while the peaks are blown away by the wind.

How are Barkhani formed and where are they located?

Barkhan dunes can form when there is large amounts of sand in the desert and a constant wind is blowing from one direction. However, if the wind direction changes significantly, the dune crescent can be destroyed. The Sahara and Gobi deserts in Africa and Asia are the most significant places where Barkhan dunes can be found.

Composition of Barkhans

The Barkhans are strikingly asymmetrical in cross-section, including a slight slope facing the sand embankment, consisting of uniform grains of sand. The Barkharn dunes have two “horns” in the wind direction. The steeper slope, also known as the sliding surface, is located downwind and is usually set at a sand wind angle of about 30-35 degrees for standard fine, dry sand. The top of the dune is filled with wind and stands at approximately 15. Barkhan dunes can be 9-30 meters high and have a base width of 370 meters, measured perpendicular to the wind. Simple Barkhan dunes are more like mega Barkhan dunes or complex Barkhan dunes, which due to erosion on the windward side slowly migrate in the wind direction and move it to the sheltered side. The speed of Barkhanen migration can be slow, with an annual migration rate of between 1-100 meters, depending on the size of the dune, as smaller dunes move faster.

Properties of Barkhan sand dunes

Barkhan dunes usually appear as individual units and can form chains that stretch across the plain in the direction of the blowing wind. Megabarkhani and Barkhanen can be combined and shaped hooves that stretch for hundreds of miles. The size distribution of Barkhan dunes in a given area is determined by changes in the collision of wind and dunes that produce new Barkhans from the horns of old dunes.

Migration of Barkhans

Due to dune migration, larger dunes are separated by smaller dunes by holding the rear end of the larger dune and then leading through the large dune to the opposite side. These processes take place superficially and mimic the behavior of solitons, but instead of moving through the medium and leaving it undisturbed, as happens in solitons, sand particles move in dunes. As the smaller dune approaches, the larger one, the wind begins to deposit sand on the dune from the back, while the sand blows from the front dune without filling up. Eventually, the front dune becomes smaller and moves independently much faster than the back dune.



Source link