Ventifact

Ventifacts are rocks that have been polished by sand transported by the wind to a characteristic, often keel- like form ( Wind Cut ).

Formation

Ventifacts arise either from rock fragments that have already been extracted from the rock composite of pending, or from larger particles (eg sand or gravel ) embedded in loose rock. They are operated mechanically by the corrasion of the wind. The sand is fluidized by reptation and saltation and acts on the rock piece as an abrasive. The prevailing wind direction facing side of the stone ( windward side ) is sanded and smoothed, while the side facing away from the wind ( leeward side ) remains largely unchanged. This results in more or less sharp burrs or edges.

Ventifacts of rocks of low hardness can already occur within a few decades.

According to the number and training of ground surfaces, a distinction Einkanter, Two Kanter and More Kanter; but very often are irregular shapes. Several edges form off when:

• Grind winds from different directions the stone from different sides
• The stone is a singly or multiply its location changes during the course of the process, for example by Solifluction
• Mapped out in carved stone structures carved out

Dissemination

Ventifacts occur almost exclusively in low vegetation or free areas ( deserts ). Depending on the prevailing climatic conditions, it can be either to dry or cold deserts. On the basis of subsequent climate changes (eg warming at the end of the Ice Age ) may ventifacts also occur as a relic in areas where they would not occur today. Therefore ventifacts are for example in the moraine landscape of northern Germany, that was during the recent, the Weichsel glaciation, a cold desert or steppe ( periglacial ), very widespread. Since there also is glacial sediment at the ventifacts, one also speaks of windgeschliffenem attachment.

As a special case can arise ventifacts also Eiskantern or at least from pre-ground by the ice stones.

The conditions for generating ventifacts are also given on Mars. Jake Matijevic ( rock) is an example of such a form of erosion on Mars.