What is the cause of the formation of aeolian forms of relief? The process of formation of the relief

Under the relief we mean the shape of the surface of our planet, which is considered in relation to a certain level. In other words, these are all irregularities in land, sea and ocean floor. Different types of relief differ in their size, age, and also the history of development.

It is especially important to take this into account at the design stage and in the construction of road, rail and other networks. Characteristics of the relief (mountain, hilly, flat, etc.) will significantly affect the amount of work and their cost.

A variety of forms of the earth's surface

All the unevenness of the land is divided into:

1. Mountains. This is a conical shape of the relief, towering above the surrounding terrain. The highest point of the mountain is called the peak, which can be either acute, or have the form of a platform (plateau). The lateral surfaces of such elevations consist of skates. The line that indicates the fusion of mountains with their surrounding terrain is the base, or sole.

2. Excavations. This form of relief is opposite to the mountain and is a closed depression. The lowest point of the excavation is called the bottom. The lateral surfaces of such a relief form are skates, and the line of their merging with the surrounding territory is a cobblestone.
3. Ridges. It is nothing but a hill, stretched in any direction and constantly falling in its height. All ridges have two slopes, which, merging at the top, form a watershed line.
4. The Dell. Such forms of relief are opposite to ridges. They are elongated, constantly falling depressions, which are open at one end. The hollow has two slopes that connect to the line of the watershed, which runs along the bottom of this formation. An example of this form can serve as a valley and a ravine. In the first case, we can speak of a broad hollow, which has gently sloping, sloped stingrays. The ravine is radically different from this formation. It is a narrow hollow, the slopes of which are steep and do not have turf.
5. Saddles. These are places that begin in the confluence of stingrays and are located between two neighboring mountains. Sometimes the saddle is located on the site of the confluence of the watersheds of the ridges. On its territory, as a rule, people build pedestrian paths or roads, calling them passes. From the saddle in the opposite direction go the hazel.

All the above types of relief are basic.

Methods of education

The topography of the surface is the individual convex or concave irregularities that can be observed on the surface of the earth. Its forms differ in size and in origin. So, all terrain on the planet is referred to as mega-, micro-, meso- or nanorelief. And their formation could be caused by water-erosive or volcanic, karstic or glacial, tectonic or eolian processes. Each of the above ways means a certain kind of movement of energy and matter in the depths or on the surface of the earth's crust.

Varieties of relief-forming processes

All factors affecting the formation of the surface of our planet, are divided into endogenous and exogenous. Despite the existing differences, they always act together. However, the predominant role of one of them depends on the characteristics of the relief in a given locality.

As for exogenous factors, they always occur on the surface of the Earth. The zone of action of such processes is the uppermost part of the soil. These factors are the formation of relief, such as erosion and weathering, abrasion and denudation, the impact of glaciers, etc. It is caused by the vital activity of organisms, gravity, the influence of solar radiation and energy. Exogenous factors, acting on the upper layer of the earth's crust, form, as a rule, meso- and microforms of the surface. This is due to their insignificant influence on the geological structures of our planet.

Large forms of relief are formed as a result of endogenous factors. These are processes occurring in the bowels of the Earth, which are caused by gravity and internal energy. Large forms of relief arise and because of certain factors that arise as a result of the rotation of our planet. How do endogenous processes manifest themselves? Their presence is prompted by the activity of mud volcanoes, magmatism, tectonic movements, etc. And all these manifestations are caused by the thermal energy of the planet arising as a result of radioactive decay occurring in the mantle. It should be said that the endogenous processes divided the earth's crust into two types - oceanic and continental.
The influence of internal thermal energy causes the movement of the lithosphere. The map of the relief changes significantly. Faults and folds, mountains and deflections of the upper layer of the earth's crust are formed.

What are the examples of the relief formed as a result of the action of endogenous processes? First of all, these are the crusts of the Earth's crust. They differ in their size and shape, as well as in terms of education time. The deepest of such faults are the largest blocks experiencing horizontal and vertical displacements. Often they are defined by the outlines of the continents. Large blocks of the Earth's crust are literally riddled with small faults. Most often these are river valleys, uplands, and also lowlands. And all these forms, as a rule, make modern vertical movements in one direction or another. So, the Central Russian Upland, where the Kursk, Voronezh and Belgorod Regions are located, has a constant rate of rise from 4 to 6 millimeters per year. But the Oka-Don lowland, on the contrary, falls. The speed of this process is 2 mm per year. It should be noted that the relief and geological structure of the earth's crust are closely related. The ancient movements of the blocks of our planet are reflected in the nature of the occurrence of the rocks in them.

To date, one of the factors affecting the change in terrain is human economic activity. There is a direct impact on the earth's crust during the extraction of minerals, during construction, as well as in the development of fields for the cultivation of agricultural products.

Wind Operation

The impact of air mass flows on the environment can be observed everywhere. The work of the wind is also a relief-forming factor, which has a particularly great influence on the territory of sand deserts. Various irregularities of the earth's surface in this case take place in connection with the effect of the process of deflation. This is the blowing of sand masses.

Also, they are transferred and further deposited (accumulated). Those forms of relief that were formed as a result of wind work are called eolian. And this is not accidental, because Aeolus is the name of the ancient Greek god of the wind. What is the origin of the relief of this kind? It is formed under the influence of the following processes:
- deflation - blowing loose soil;
- Corrosion - grinding and grinding of hard rocks;
- ground transfer by air flows;
- accumulation of materials.

The speed of the wind is directly related to the transport of ground particles located on the surface of the Earth. So, when the flow of air masses moves within one second to a distance of 4.5-6.7 meters, grains of up to 0.25 mm can move. At a higher speed (11.4-13 m / s), their value can be up to 1.5 mm.

Forms of deflationary relief

The processes of blowing loose soil often occur on arable land given to agricultural land. What is the cause of the formation of aeolian relief forms in this case? The deflationary process is due to the loss of the structure of the humus horizon as a result of plowing the land for a long period. The soil begins to be easily blown out, and the scale of this phenomenon reaches up to 125 tons per hectare. The deflationary processes are also taking place in the Russian Central Black Earth region. For example, in 1967 in the south of the Voronezh region a raging dust storm demolished about 60 tons per hectare of soil.

Description of the terrain of territories on which there is partially fixed vegetation is an alternation of the basins of blowing and the partitions located between them. This is the so-called landscape of cellular sands, which is formed when the soil particles are scattered unevenly by air masses of variable direction. In stable winds, the basins acquire a crescent shape and have a definite directivity. They are called so: hole aeolian sands. The largest similar forms have up to seventy meters of depth. They are often found in Arabia, where they are called Fulgi.

Forms of corrosive relief

The sand masses transported by the wind often grind and soak the surface layers of those rocks that occur along the path of their movement. Thus there is an education:
- Corrosive niches;
- "stone pillars";
- eolian "stone mushrooms".

As for the corrosive niches, their formation occurs, as a rule, in easily degradable rocks. They, for example, are marls and sandstones. If loose rocks are covered more dense, then the formation of "stone mushrooms" or "stone pillars" occurs. This is an amazing form of relief in its beauty. They can resemble pillars, towers or mushrooms.

How does this miracle of nature form? Air masses carry together with their flow the smallest weathering products, as well as flocculations of loose material. Large in size sand masses are in contact with rock. In this case, the soil particles act as an abrasive material. They grind and grind the surface of the rock. As a result of this influence, peculiar eolian forms appear in the form of pillars and fungi.

Sometimes the wind blows whole hollows in loose material. These are oval or rounded forms, having from several tens to several hundred meters in diameter. Sometimes the basins of blowing are like furrows. Then they are called yards. Such furrows are often formed along roads or other formations with elongated dimensions.

Accumulation forms

Any of the streams of air masses has its capacity, power and saturation. The first indicator characterizes the amount of sand that the given wind force can move . The power is determined by the actual number of transportable soil particles. And what is the saturation of the wind? This is the ratio of the power of the air flow and its capacity. For small values of this index, deflation processes occur, and for large ones, accumulative ones. Consider the action of the last of them.

What is the cause of the formation of aeolian relief forms of accumulative type? All the same work of the wind carrying particles of sand. When a bush or any other obstacle is encountered on the way of such a mass, a mound of calligraphy is formed. Collecting, the sand completely covers the plant.

There are various examples of relief formed by accumulative processes. But all its forms are divided into two types:
- longitudinal;
- transverse.

Longitudinal forms include sandy ridges, which are called ridge sands. Their formation is due to the action of winds of constant direction. Such a process causes the sand to be blown out of the lowlands with simultaneous ejection of it to the elevations or ridges that form at the same time. At the same time, soil particles move along the direction of wind movement along the crest, which contributes to the constant elongation of this shape.

Among the transverse accumulative eolian formations are barkhans, barchan chains and dunes. Let us consider them in more detail.

Barchanas

In the deserts, it is often possible to find hills of sickle-shaped form, the peaks of which are pointed and facing the prevailing action of air masses. This is the barkhans. What is the cause of the formation of aeolian relief forms of this kind? All the same wind work. Barkhans have asymmetrical slopes. With their gentle side they face the windward side, and the steep side - to the leeward side. Barkhans are mobile forms of sandy relief. Their movement is slow, but constant. During the year it is 50-60 meters. In Karakum, this speed is much higher. It is 12 meters for a month.

What is the cause of the formation of aeolian relief forms of this kind? Of course, the work of frequent and strong winds. However, there are some other factors, under the influence of which there are barkhans. These include:
- a small amount of precipitated precipitation;
- active physical weathering of land rocks;
- small number or total absence of vegetation.

In what conditions is such a relief formed? The climate of the deserts of the tropics and temperate latitudes is very conducive to the emergence of barkhans. The height of such sandy formations, as a rule, is no more than eight meters. But some of the broadest of them can climb up to 40 m.

Barkhan chains

These are the eolian forms of relief, which rise above the surface of the earth by separate ridges. They are a few merged barkhans. Description of the relief of this type often contains an indication of the presence of signs of ripples, located on the windward slopes. These are small, parallel-directed rollers of sand, whose height is within 2-5 cm. The appearance of the ripple marks is caused by the oscillation of air masses.

Dunes

In the extratropical deserts, eolian formations of the transverse form can often be observed. These are the dunes. Under the influence of wind, similar formations can take a longitudinal form. Sometimes dunes resemble dunes in their appearance. However, in contrast, the "horns" of such formations are directed towards the wind. By outlines of contours such dunes are called parabolic.

What else are the eolian forms of relief? They include those dunes that are leaning and pyramidal. Such formations are the largest of the aeolian. You can see them in Central Asia and in the Sahara. Pyramidal dunes are formed when winds blow in different directions. Sometimes such forms reach a height of 150 meters. The leaning dunes are formed near mountain ranges. This is a kind of sandy trail, inspired by air masses on the slope. The leaning dunes often have a height of 200 m.

Other eolian formations

Often the mobility of soil particles restricts vegetation located in the area of their distribution. Thus, in the presence of rare layers of fauna, hilly sands form. Kuchugurs take place in the sand valleys and on the sea coasts. This is the so-called cumulus sands.

In the arid countries, not only sandy, but also stony, as well as clayey deserts are widespread. Here one can observe the formation of various deflationary forms. Thus, the protrusions of rocks in stony deserts are often covered with so-called desert tans. It is a brilliant crust formed as a result of capillary drawing of salt solutions from the stone. Most likely, microorganisms that concentrate hydroxides and oxides of iron, manganese and other chemical elements participate in this process.

On the surface of clay deserts there are loesslike rocks. That is why the relief in this area is composed of closed shallow depressions having an even bottom. They call such formations takyrs. Their surface is covered with a clay crust, which is broken by a whole network of cracks. With rare showers in takyrs, water accumulating the upper layer accumulates.

For the relief of arid regions, there are also drainage depressions. The rainwater collected in them has no way out. Similar depressions can stretch for hundreds of kilometers, reaching a depth of 200 m. Such formations can be seen in the Libyan desert. It is the hollow of Kattar, the absolute mark of which is minus 134 m. In the formation of such forms, not only the wind takes part. A great role here is assigned to lithological and structural-geological conditions. In some places such depressions are buried beneath a layer of sand.

It is interesting that takyrs are constantly deepening. This is due to the fact that the wind destroys and blows the clay crust on their surface. Such deflation processes lead to the formation of clayey sand dunes. Such forms can be found on the territory of Mexico.

The landscape of the subtropical and tropical zones adorns the remnant or island zones, as well as the denudation plains. These forms are formed under other climatic conditions, but still they are most typical for deserts.

In the relief of Central Asia, there are denudational stratified plains, complicated by table-and-bottom elevations. These are island ridges with flat peaks and abrupt steep slopes. Similar forms in Central Asia are called turtles. Their formation, perhaps, was initially facilitated by the erosion of unstable watercourses, and then the main role was assigned to the processes of deflation caused by the operation of the wind.