Earth and Moon

Wind erosion

Wind erosion

Compared to water, wind is a less intense erosive agent, but in dry regions it acquires a very special importance. In these arid zones, the wind has formed the deserts, which constitute a very large surface throughout the Earth.

The constant wind forms structures as well known as the dunes, but also produces other very particular and sometimes spectacular forms in the rocks of the regions where it acts with greater intensity.

The erosive action of the wind

The wind, by itself, does not have enough force to produce weathering effects. What it can do is transport particles that, when they collide with the ground, wear it down. This type of erosion is usually slow and, for it to occur, the territory must be bare, since the vegetation decreases or cancels the effect.

Wind erosion occurs, then, in arid areas, such as deserts and high mountains. These also have another essential feature: the large temperature differences. This causes the rock to break and wind erosion can act more effectively.

Corrosion is the abrasion suffered by rocks when they are fricted by the impacts of the sandy particles that are transported by the wind. When these particles hit the rocks they undergo a transformation, taking on a rounded appearance. When the wind loses strength, it gradually deposits the materials transported, which usually results in the accumulation of particles of similar size and weight.

DesertContinent PlaceSurface (km2)
SaharaAfricaNorthern half 9.100.000
LibyaAfricaNE of the Sahara1.680.000
Australian AustraliaCentral region1.550.000
ArabicAsiaArabian Peninsula1.300.000
Deserts of the Earth

Deserts and dunes

Generally, an area whose annual average rainfall is less than 250 mm and where, in most cases, evaporation exceeds precipitation as a result of a high average temperature is called desert. Due to the lack of moisture in the soil and in the atmosphere, the sun's rays strike strongly. Temperatures during the day can reach 55 ° C in the shade; During the night, the desert floor radiates heat to the atmosphere and temperatures can drop to freezing.

The dunes are like mountains of sand that form in the deserts, although they also do so on the edge of the lakes and the sea, where the winds are strong and tend to blow in only one direction. The dune fields extend over thousands of square kilometers in the deserts of North Africa, on the Arabian peninsula and in Central Asia.

The wind, when moving the grains of sand, causes the height growth of the dunes, as well as their transfer. A growing dune can move up to 30 m per year. The face that opposes the wind is always longer and less steep than the opposite face.

The deposits of ancient dunes that are buried are transformed into sandstone, which has an asymmetric stratification, called cross stratification, which reveals the direction of the wind that originated it.

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