Yardang

A Yardang (or Jardang, occasionally wind cusp ) is a geomorphological, erosion tabular form in unconsolidated sediments (mainly lacustrine sediments in shallow stratified ).

The explorer Sven Hedin has Yardangs first named and described, as he crossed the Chinese Lop Nor desert in 1903. The word Yardang he derived from the Uighur word Yar, that with a steep wall of sand (English: ridge or steep banks ) may be translated.

Formation

Fundamental to the emergence

Yardangs arise from the interaction of deflation, wind touches ( corrasion ) and at times the onset of water erosion. The final shape is formed by corrasion, ie by wind touches the constantly blowing wind from one direction; entrained by the wind sand sands out the structures from the underground. Initial forms of Yardangbildung are eg gutters by runoff events, large drying cracks, but also tectonic adjustments and crevices. These disturbances of the wind can start its concentrated on streets abrasive action. It created layer step-like formations, which are caused by changing resistance of the sediments.

In these processes creates a streamlined ( drop-shaped ) body with wide and narrow Luv Lee.

Process of morphogenesis

The steep windward side is formed by Kornimpakt, updraft and counter flow. At the back and flank the air is accelerated, at the widest point, the boundary layer is lifted and underneath it a counterflow, in the Lee form vortices when the currents meet. These erode the Yardang from behind. Is the streamline shape reached acts on the Yardang almost exclusively deflation, because the boundary layer is not lifted.

Dimensions and shapes

The ratio of length to width is approximately 4:1. Yardangs come in orders of magnitude from the range of centimeters to several tens of meters ( in some cases even larger) on.

Occurrence

Known occurrences on earth are the Yardang fields in Iran (these are called Shar = Lut Desert Cities ), the Yardangs the Lop Nor desert and the particularly pronounced Yardangs in the Sahara, which are found between the Hoggar, Aïr and Adrar des Iforas.

Although the planet Mars has a very thin atmosphere, Yardang structures could be detected in many regions of the planet, were allowed to form over a long period by wind erosion. This sheds light on the dynamics of the wind conditions on the Martian surface.

So Mensae were from the European Mars Express spacecraft in the region Aeolis discovered next mesas Yardangs and near the Martian equator, west of the Tharsis region, pronounced Yardang structures; these are (Greek back of the Furies ) sector dominated by volcanic area of the Eumenides Dorsum. Another site that caused by wind erosion structures located near the shield volcano Olympus Mons, the highest mountain in the solar system.