The eolic erosion It is the wear caused by the action of the wind on a surface exposed to it. This wear occurs as a function of the wind speed, the particles it carries and the resistance of the substrate on which it acts..
For each erodible surface there is a minimum wind speed required for erosion to exist. It depends on the size, density and cohesion of the particles that make up the substrate..
If a soil is composed of particles that are loosely cohesive with each other and are lighter, they are blown away by relatively weak winds. While factors such as vegetation, climate, soil characteristics and topography influence the action of wind erosion.
Depending on how these factors are expressed, various types of wind erosion occur, which are effluction, extrusion, detrusion, efflation and wind abrasion. The action of any of these forms or their combination has serious consequences.
Some are the loss of soil and desertification, the deterioration of infrastructure and equipment, and environmental pollution. The latter in turn leads to public health problems.
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Wind erosion begins with the detachment of the particles by the pushing action of the wind. Then, these particles are dragged a certain distance, to be finally deposited (sedimentation).
This process is in turn affected by factors such as climate, vegetation, the shape of the land (topography) and the characteristics of the substrate..
Temperature and humidity are the most relevant elements of the climate in relation to wind erosion. The first affects both the formation of wind currents and the cohesion of the erodible particles..
In the first case, winds are formed when high temperatures in an area heat up the air masses. When they rise, they form an area of low pressure towards which the air masses flow, forming winds..
High temperatures cause the loss of moisture from the soil and rocks, which weakens their cohesion. In addition, the temperature differences between day (high) and night (low) cause expansions and contractions that crack the rocks and facilitate the erosive action of the wind..
Therefore, in dry and hot climates where these high fluctuations between day and night temperatures occur, there is greater wind erosion..
The vegetation cover protects the soil from the dragging of the wind and in the case of tall vegetation, the speed of the winds decreases. In addition, the root system of the plants and their contributions of organic matter, contribute to give cohesion to the soil particles..
Depending on the shape of the land, wind erosion will be less or greater due to the ease of movement of the wind. Thus, on flat terrain without many obstacles, the wind speed is high and its erosive power increases..
For their part, large geographical obstacles reduce the speed of the winds, but if their height is low they can generate turbulence. Turbulence depends on the initial speed of the winds and the shape of the terrain.
These turbulences raise the finest particles to high altitudes and can be transported long distances..
The cohesion or degree of union between the particles that make up the soil, a rock or any surface is fundamental, because when the cohesion is lower, lower winds are required to erode the structure..
On the other hand, the size of the particles susceptible to the action of the wind also influences. In general, it is established that for particles between 0.1 and 0.5 mm, winds of at least 15 km / h at a height of 30 cm are required to move them..
As the particles are larger, higher speed winds are required to move them. On the other hand, the size of the soil particles or rock fragments determines the type of wind erosion that acts.
It is the direct removal of small particles (0.1 to 0.5 mm) by the pressure of the wind, which is pushing these particles by leaps. While the smallest can even be suspended.
In this case, they are thicker particles that cannot be removed directly by the wind. However, the push of the smaller particles causes their displacement.
In this process, it is the particles from the crests of irregularities in the terrain that are removed by the wind. Here the thrust force of the wind is combined with the gravity effect of the slopes.
It consists of the lifting of fine particles from the soil that are incorporated into the turbulence of the wind. In this way they reach high altitudes and are transported long distances..
The finest particles remain in suspension, representing a serious contamination problem. On the other hand, depressions called deflation depressions form in eroded areas..
The erosive effect is generated by the particles that the wind carries and impact on the surfaces. It can be on the ground itself, releasing additional particles, on rocks or on infrastructures.
This horizontal shower of particles acts like sandpaper that wears down surfaces and, when turning in sandstorms, causes serious damage. Sometimes they carve rocks into peculiar shapes, called ventifacts or artifacts made by the wind..
In severe cases, wind erosion ends up dragging the fertile layer of agricultural soils, leaving the thickest particles. This in turn causes the loss of soil fertility and desertification, with the consequent impact on food production..
When the wind has blown away all the fine particles, leaving only the coarse material, the highest level of wind erosion is reached. This coarse-grained material forms a continuous layer that is called desert pavement..
When the transport of soil particles is very large, the subsequent sedimentation can interrupt roads and affect cultivation areas, industrial and urban areas. On the other hand, the abrasive effect of the particles deteriorates equipment and buildings by wearing down materials..
Fine particles in suspension are pollutants and one of the causes of respiratory diseases. In fact, one of the parameters that are measured when defining atmospheric pollution is the particles in suspension, both their quantity and their size..
They are called PM10, PM5 or PM2.5, referring to material particles of 10.5 p 2.5 µm respectively. The smallest ones penetrate deep into the pulmonary alveoli causing serious health problems.
This was a gigantic wind erosion process that became one of the worst ecological disasters of the 20th century. It affected the entire central region of the United States of America, including Texas, Nebraska, New Mexico, Oklahoma, Kansas and Colorado.
This occurred between 1932 and 1939 and was one of the factors that aggravated the Great Depression of the economy at that time. The cause was the combination of a previous period of exceptional rains and an overexploitation of agricultural fields.
This was followed by a long period of severe drought, which left the soils exposed to the action of the wind. Being a region of great plains, the winds reached high speeds generating sand storms that caused the desertification of large areas of the central United States..
As a result of this phenomenon, more than 3 million people abandoned their farms and many emigrated, especially to the west of the country. Deflation depressions were formed in some areas due to a reduction of up to 1 m in depth.
In Argentine Patagonia there are around 4,000,000 hectares of dunes and desert pavements, the most acute phase of wind erosion. By adding other degrees of erosion, the figure of 13,000,000 has been affected.
In this case, the dry climate is combined with overgrazing by sheep and between 1957 and 1988 the wind erosion rate was calculated at 175,000 ha per year. In the semi-arid Pampa with a surface area of close to 24,000,000 ha, it is estimated that 46% of this area is affected by wind erosion..
In this area, deforestation, overgrazing and inadequate agricultural work have led to the action of wind erosion..
The arid regions of North Africa are the largest source of dust in the world, where winds blow large clouds of dust westward as far as the Americas. In fact, in mid-2020 a cloud of dust from the Sahara darkened the skies in various areas of the Caribbean..
In places like Martinique, Guadalupe and Puerto Rico, they decreed a maximum alert for unusual levels of air pollution with suspended particles (PM10). Levels between 400 and 500 µg / m were recorded3, being 10 times more than acceptable.
Although this phenomenon is annual, this time it was pointed out as the most intense in 50 years.
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