Basic forms of sand dunes. Desert dunes. View from space

Is it possible to imagine all the beauty of the East if, closing your eyes for a second, you do not see the desert stretching to the horizon. Tons of hot sand, from which hot air rises, distorting the picture. A caravan of slow-moving camels loaded with oriental textiles and other goods, a high sun and intense thirst that torments travelers. Such an association does not arise by chance, because when it comes to the desert and sand dunes ah, this colorful picture involuntarily arises. What is a dune? What does this word mean, and where else, besides the eastern deserts, are such natural sand embankments located, we will try to figure it out in this article.

Correct Definition

A dune is a natural mound of sand that lives its own life, which, in strong winds, can move up to several tens of meters, changing its shape almost beyond recognition. From the side where the wind rules the show, the dune looks like a silk fabric that someone has very carefully spread out. She is sloppy. Sometimes you can see the absolutely flat surface of the dune, and sometimes its surface becomes like the surface of the ocean, slightly upturned by small ripples of barely noticeable waves. It is also not uncommon for sand patterns to be twisted in a spiral or in a chaotic manner on the gently sloping sand dunes. The other side of such a natural hill is a steeper slope, where millions of small grains of sand fall down from the very top. This is how the dune moves, driven by gusts of wind. In scientific articles, encyclopedias and other "smart" books aimed at development and self-education, one can come across the wording that a dune is a positive landform. This interpretation is due to the fact that all natural bulges that rise relative to sea level, which are located on our planet: mountains, hills, dunes - are considered to be striving in a positive direction (in this case, up).

Where can be found in nature

Sand dunes are located not only in deserts, they can delight with their incredible miraculous beauty, lying in the steppes, forests, in areas open to the wind and in coastal zones rivers, lakes, seas and oceans. If we talk specifically about the desert, then calling its huge dunes sandy hills does not turn the tongue, but in the steppes this wording is quite suitable. Still, the scale of the Sahara or the Karakum does not allow the use of this term, it is small and does not reach the huge size of the world's largest deserts. The wording "giant sand dune" is more appropriate here.

The danger posed by the sand hills and other most beautiful places on the planet

In addition to their splendor and incredible breathtaking beauty, sand mounds harbor hidden threats. It is worth noting that the dune is a place where you must always be on the alert. In nature, this happens all the time - most charming places our planet hide many dangers, sometimes even deadly. For example, Paradise Island Queimada Grande, not far from the Brazilian Sao Paulo, has long been closed not only for local life, but also for tourists. This is because the most venomous snake in the world (the island botrops) has completely conquered this place for itself from people. Another example is the road over the precipice in Bolivia. A narrow serpentine of clay, stones and landslides attracts millions of tourists to look at the beauty of the Amazon. It is considered aerobatics to overcome such a road of death on a bicycle. About 300 people die there every year, but the place does not lose its popularity. Beauty is a terrible force.

What is the danger of sand dunes? What is so terrible in store for people this bewitching element? It's simple - they can meet there quicksand. There is no way to determine their specific location, they look exactly the same as the entire surface of the sandy area. From ancient times to this day in the East and Africa there is one tradition: when a caravan with provisions sets off through the desert, a Tuareg always runs ahead of it - a boy of 7-10 years old. This guy is the guide of the entire caravan. First, he makes a path and finds out if the road is fraught with danger in the form of quicksand. Then he returns to the caravan and shows the safe way. The main advantage of the Tuareg is its light weight. It is believed that even if you get into quicksand, then there is a chance to get out alive and unharmed. To do this, you need to be calm, do not make sudden movements, try to lie on your back, spreading your arms.

Nature creates masterpieces

We must pay tribute to nature, which knows how to create its own unique masterpieces, like the most skilled craftsman. Sand dunes should be recorded among her best works, and the answer to the question "what is a dune" will be laconic - "natural masterpiece".

Dune

Dune

a positive form of relief of the sands of non-desert areas created on the coasts of seas, lakes and rivers, within the limits of outwash periglacial plains. There are transverse, longitudinal and parabolic dunes. The shape of the latter (non-desert dunes) is inverse to the shape dunes: the steep leeward (or leeward) slope of the sand fall is convex in plan, and the windward slope is shaped like horns pointing upwind, giving the dunes a parabolic shape. Often the horseshoe of a parabolic dune is not symmetrical: one horn may be longer than the other. Relative height dunes vary from a few to hundreds of meters. Dunes can be bare or covered with vegetation. Abroad, the term "dune" is any relief of sands created by the wind in deserts, on low sea shores, in floodplains, regardless of vegetation and climatic conditions.

Geography. Modern illustrated encyclopedia. - M.: Rosman. Under the editorship of prof. A. P. Gorkina. 2006 .

a sand hill formed as a result of aeolian (wind) activity. Dunes are common wherever loose sands come to the surface, and the wind speed is sufficient to move them. They tend to form when sand builds up against an obstacle such as a bush or a rock; then the dune itself becomes an obstacle and gradually increases in size as the sand winds up. The dunes are up to 300 m high. Their dimensions are determined by the volume of incoming sand, wind speed and steepness of the slopes.
In areas where the direction of the wind is constant, the dunes acquire characteristic outlines: gentle windward and steep leeward slopes, and in plan - the shape of a crescent. Max Speed dune movements - approx. 30 m per year. On the coast Baltic Sea recorded the movement of one dune by 13 km in 60 years. There were cases when the dunes covered settlements and forests, sometimes as a result of their further movement, previously buried objects were dug up. Moving dunes are fixed with artificial plantings of pine and sown with grass. Dunes are found along the shores of the seas, lakes and rivers, in the beds of dry streams and in deserts. Aeolian forms of deserts are classified as dunes.

Encyclopedia Around the World. 2008 .

See what "dune" is in other dictionaries:

dune- uh. dune f. This is the name of coastal sandbanks rising above the water. Vavilov 1856. Sand hills formed on low banks seas, lagoons. rivers, lakes under the influence of wind and continuously moved by it. ALS 2. Suddenly nature ... ... Historical Dictionary of Gallicisms of the Russian Language

Hill, dune Dictionary of Russian synonyms. dune n., number of synonyms: 3 dune (4) hill (61) ... Synonym dictionary

- "DUNE" (Dune) USA, 1984, 140 min. Fantastic. An adaptation of Frank Herbert's sci-fi bestseller about Planet Dune from 10991. Cast: Kyle MacLachlan (see MacLachlan Kyle), Francesca Annis, Brad Dourif, Sting, Dean Stockwell, Linda Hunt, Max… … Cinema Encyclopedia

Y, well. (German Dune). Coastal sand hill, wind-blown drift. dune pertaining to a dune, dunes. || Wed dune, drumlin. Dictionary foreign words L. P. Krysin. M: Russian language, 1998 ... Dictionary of foreign words of the Russian language

dune- — EN dune A low mound, ridge, bank, or hill of loose, windblown granular material (generally sand, sometimes volcanic ash), either bare or covered with vegetation, capable of… … Technical Translator's Handbook

dune- dune Düne - a hump of a wind-blown dog. Beyond the cordon, D. is a wild term for all forms of landscape relief, like the creation of a fiery wind ... Girnichiy encyclopedic dictionary

dune- Sandy landform created by the activity of the wind in deserts, on low sea shores in different climatic conditions→ Fig. 98… Geography Dictionary

This term has other meanings, see Dune (meanings). "Sand dune" redirects here; see also other meanings ... Wikipedia

A sand hill formed as a result of aeolian (wind) activity. Dunes are common wherever loose sands come to the surface, and the wind speed is sufficient to move them. They tend to form when sand... ... Collier Encyclopedia

dune- kopa statusas T sritis ekologija ir aplinkotyra apibrėžtis Vėjo supustytas smėlio kalva arba kalvagūbris dykumose, smėlėtuose pajūriuose, paežerėse, paupių, zandrinėse lygumose. atitikmenys: engl. dune; Dunes vok. Dunen, f rus. dune, f; dunes… Ekologijos terminų aiskinamasis žodynas

Think all sand dunes are alike? Think again! Below are some ways to tell sand dunes apart.

Sand dunes are amazing creations nature. These are mounds, consisting of loose grains of sand, raised by the wind and collected in one place, forming a small hill. Sand dunes cannot appear without sand and wind. Most dunes form in deserts and sandy beaches. Huge sand dunes in the Sahara desert are called sand seas. Understanding the types of sand dunes and their formation contributes to the development of infrastructure facilities such as gas and oil fields. It also helps control the movement of the sand. The five main types of sand dunes are stellar, linear, parabolic, dune, and reversible sand dunes. The speed, turbulence, and direction of the wind determine the shape of the sand dunes. In addition, the amount of sand available also affects their type. For example, star dunes only form when there is a large number of sand.

stellar

Star sand dunes are pyramidal in shape. They form in places with multidirectional and strong wind regimes. In addition, their formation requires a large amount of sand. Star dunes grow up and out. They have three or more ridges that radiate from a central point. The gliding surface of stellar sand dunes continues to change with the flow of the wind. Apart from the pyramid shape, the star dunes are the tallest dunes on Earth. For example, the star dunes in the Badyn Jaran Desert in China reach 500 meters in height. Another example of star dunes is found in the Great East Erg of the Sahara Desert. In other deserts, star dunes form near topographical barriers around the edges sandy seas. Star dunes make up 8.5% of all sand dunes in the world. Other places where star dunes occur include Mexico, as well as the eastern Rubal Hali, located on the Arabian Peninsula.

Linear

Linear sand dunes are the longest type of sand dunes on the planet. They can extend for 120-200 km, for example, in the Sahara desert. In addition, they are straight, regular and serpentine in shape. A characteristic feature of linear sand dunes is the ridge. The dunes appear to be isolated and large symmetrical peaks. Kilometers of gravel, sand and rocky intermediate corridors separate them from each other. In addition to the straight shape, some linear sand dunes combine to form a Y-shape. Linear sand dunes require strong winds from both directions. Simply put, linear dunes form in bidirectional wind patterns. Most of them spawn in desert areas where there is barren land between the dunes. Also, linear dunes have long axes that extend in the direction of sand movement.

Parabolic

A parabolic sand dune is an inverted crescent-shaped dune that has vegetation-bound tips. Sometimes it seems that they are U-shaped. The ends of the parabolic dune indicate the direction of the wind. On the other hand, a steep slip surface points to the leeward side. The longest known parabolic dune ever recorded has a trailing arm nearly 12 km long. Parabolic dunes form when vegetation begins to appear at the ends of a sand dune. Their formation requires a moderate amount of sand and strong winds. Most parabolic sand dunes form near coastal areas and are typically found in coastal deserts.

dunes

The dunes are crescent-shaped dunes. They have a steep, slippery slope and the ends point away from the wind. The dunes are separated from each other and are constantly moving across the surface of the barren deserts. In most cases, the formation of dunes occurs where there are limited areas of sand. In fact, deserts that have many dunes are inland and open. Barchans are the most common type of sand dune compared to others, found both on Earth and on Mars. They are wider than long ones and can be 9-30 m long and 370 m wide.

Barkhans form where the wind blows consistently from one direction. They move faster across desert surfaces than any other dune, which is why dunes are the fastest moving sand dunes. The speed of their movement can be from 1 to 100 meters per year. For example, in Chinese province The Ningxia dune group moved 100m annually between 1954 and 1959. The Western Desert in Egypt also has dunes crossing the desert at a speed close to the dunes in Ningxia. The largest dunes on Earth are located in the Taklamakan Desert, China. Barchans are also found on sea beaches.

Reversible

Reversible sand dunes can be found in areas where the wind periodically reverses its direction. Wind blowing in opposite directions has a balanced combination of duration and strength. An example of reversible sand dunes is found in Algodona, California. These dunes form where rainfall is plentiful. Reversible sand dunes can move horizontally for a limited distance due to seasonal shifts in wind direction. They have two sliding surfaces: primary and secondary. The secondary sliding surface points in the opposite direction from the primary primary sliding surface. Reversible sand dunes grow vertically.

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The relief of our planet is amazingly diverse. In this article we will talk about dunes. How and where are they formed? And what are these picturesque natural formations?

Eolian relief. Dunes are...

Geography studies not only countries and cities. The sphere of interest of this science also includes the relief - the totality of all the irregularities on the surface of the planet Earth. Geomorphology (a special branch of geography) studies its main forms, genesis, and distribution.

The relief is different. Almost all the forces and phenomena observed in our world are involved in the process of its formation. So, some forms of relief arise under the influence of the internal energy of the Earth, others are formed by permanent or temporary watercourses. But the dunes are nothing more than a classic product of the work of the wind.

A dune is one of the forms of the so-called eolian relief. This term comes from the name of the ancient Greek character, the demigod Aeolus. According to myths, he is the main lord of the winds.

Eolian processes are accompanied by the transfer of small sandy, clayey or silty particles over certain distances, their accumulation and distribution over the earth's surface. The most suitable conditions for these processes are in the zone of deserts and semi-deserts, where the sediment material is not fixed by the root systems of plants.

The main forms of the eolian relief are dunes and dunes. These are sandy natural formations that differ from each other in shape, size, and also the place of their formation. Barchans are formed exclusively in deserts, have a crescent shape and reach a height of 60-70 meters. In turn, the dunes are a smaller form of relief, widely found along the shores of lakes, seas and major rivers. They will be discussed in more detail below.

Dunes - what is it? Formation and main types of dunes

If there are bushes, boulders, remnants of walls on the coast of the sea or any large body of water, then this is an excellent prerequisite for the formation of the described landform. What are dunes? These are, in simple terms, sandy hills created by the wind. Tiny grains of sand accumulate over time near some obstacle. This is how dunes are formed, the shape of which in plan depends on the wind rose of a particular area.

The heights of the dunes, as a rule, range from 20 to 40 meters. In some parts of the planet, real sand giants are found up to 100-150 meters (for example, on the shores, their windward slope is usually gentle (about 10-15 degrees), and the leeward slope is about twice as steep. Single dunes are quite rare. Most often they form elongated chains of hills of sand.

Depending on the shape, dunes are divided into three types:

• horseshoe-shaped (formed when the wind blows in approximately the same direction all year round);
• transverse (formed in places with big amount sand);
• stellar (the most picturesque dunes, formed in places where the wind often changes its direction).

dune movement

These amazing natural formations are also moving! This happens, again, under the influence of the wind. He rolls grains of sand from one slope to another, forcing the dunes to change their position in space. Their speed of movement is low - about 20-30 meters per year.

It is important to note that dune movement is a real problem. After all, wandering sandy hills destroy crops in the fields, fall asleep roads, pastures and even entire villages. People are trying to fight this phenomenon by fixing the sands. To do this, grasses, trees and shrubs are planted on the windward slopes of dunes and dunes. With their root systems, plants keep grains of sand from further "journeys".

The most famous dunes of the planet

France, Namibia, Russia, Wales and Australia - what do all these countries have in common? That's right - the dunes! Each of them has its own "miracle of sand". Let's talk about them in order.

Dune Pyla (France) is the highest in Europe. It is located on the shores of the Arcachon Gulf of the Atlantic and has a height of 130 meters. This place is very popular among tourists. Interestingly, every year Pila moves several meters deep into the centuries-old pine forest.

"Big Daddy" (Namibia) - the highest dune (304 meters). The conquest of this orange-red sandy mountain is a must for any tourist who comes here.

Efa height (Russia) - the most interesting natural object located on the Kaliningrad region. Max Height this dune - 64 meters. A special hiking trail leads to its top.

Dune Inislas (Wales) - one of picturesque places in this part of Britain. Moreover, Inislas does not look lifeless at all, it is almost completely covered with beautiful herbs and wildflowers. In addition, the dune is unusually mobile and constantly changes its shape.

Mount Tempest (Australia) is considered the second highest dune in the world (285 meters). It is located in the northeast of the country, near the city of Brisbane. The dune attracts the attention of not only travelers, but also professional photographers, because from its top a wonderful view of the Australian coast opens.

Conclusion

So, the dunes are a landform of eolian origin. That is, its main "builder" and "sculptor" is the wind. Dunes form on the shores large reservoirs, are characterized by small size and mobility.

Dry and seemingly endless deserts are more than just heat, dry sand and the absence of life. In fact, deserts are an amazingly beautiful part of our planet, hiding many mysteries. This collection contains interesting, unusual and beautiful pictures the most beautiful deserts in the world. We have already written about many of them separately, so I advise you to follow the links in the articles and read more about these wonderful corners of the world.

Let's start with a landscape of the Nile River Valley in Egypt and a road interrupted by a sand dune:

And here are the amazing crops with spot irrigation in the desert of Jordan:

The following landscape was captured in the Huacachina oasis in Peru. This settlement was built near a small natural lake in the middle of the desert and is very popular not only among residents of nearby cities, but also among visiting tourists.

Laguna in national park Lencois Maranhensis in Brazil, one of the most beautiful places on the planet. This is about 1000 square kilometers of soft white sands with oases of colored lakes evenly distributed over them.

Sand dunes of Rub al-Khali on the border of Oman, UAE, Saudi Arabia and Yemen. This place can be added to the list of not only the most unusual deserts, but also the most unusual borders of the world.

Giant sand dune and climbing wanderer in Namibia:

Withered acacia trunks and surreal landscapes on the Sossusvlei Plateau in the Namib Desert:

The following photo was taken in the Egyptian National Park called White Desert. Once upon a time, this desert was the bottom of the ocean, and after the water left, it became one of the most beautiful places not only in Egypt but all over the world

This beautiful shot was taken in the desert in the south of the Australian continent:

The Takla Makan Desert in China is considered one of the largest sandy deserts in the world:

Another beautiful scenery from China, the oasis of Yueyaquan Lake in the Gobi Desert:


Aerial view of a dry river bed in the Sonoran Desert in Mexico


Ivanpah solar power complex in the Mojave Desert in California, USA:


Camel caravan in the Sahara desert in Niger. The Sahara is one of the most big deserts world, actually covering 30% of the territory of the entire African continent. On top of that, it is the hottest place in the world, where temperatures often exceed 50 degrees Celsius.

We return again to the Rub al-Khali desert and its strange formations. The picture shows a bizarre network of dunes, inspired by the winds blowing in a certain sequence for many centuries.


Pinnacles Desert and its bizarre pillars, Australia:


Lake Ouem el Ma in the desert of Libya:


Again national park Lencois Maranhensis in Brazil:


Bareina desert village in Mauritania:


The Namib Desert meets Atlantic Ocean, Namibia:


arid landscapes