Why are there deserts? 5. Why is there a desert?

To put it simply, it's caused by the tree being cut down.

When the earth first started, it seemed that there were no deserts! But because the place is so dry, coupled with the destruction of human beings, the water resources in some places are wasted! Without water, it's a desert!

l) Unreasonable farming.

2) Overgrazing.

3) Unreasonable woodpicking.

Chinese name: desert.

English name of desert: sandy desert; desert

Definition 1: The product of a dry climate on the earth's surface, generally with an average annual rainfall of less than 250mm, sparse vegetation, less surface runoff, and obvious wind action, resulting in a unique landform pattern. Such as all kinds of sand dunes, wind erosion and bad ground, etc.

Discipline: Geography (first-level discipline); Desertology (secondary discipline).

Definition 2: An area covered by quicksand and sand dunes.

Discipline: Soil Science (first-level discipline); Soil Erosion and Soil and Water Conservation (Secondary Discipline).

Causes: Desertification can be understood as a kind of desertification, that is, after the destruction of vegetation, the ground loses cover.

Desert. Under the action of arid climate and high winds, the green fields gradually turn into desert-like landscapes. Land desertification occurs mainly in arid and semi-arid areas.

The key factor in the formation of the desert is the climate, but in the edge of the desert, the native vegetation may be grassland, which is desertified due to human reasons, and these human factors are mainly the following aspects: (l) unreasonable agricultural reclamation. Whether in desert areas or native grassland areas, once reclaimed, the land will be desertified.

From 1958 to 1962, a one-sided understanding of large-scale agriculture was carried out, and in pastoral areas, semi-agricultural and pastoral areas, and agricultural areas were indiscriminately cultivated, and in 1966 and 1973, a one-sided emphasis was placed on grain as the key link, saying that "herdsmen do not suffer from the loss of grain." As a result, the phenomenon of indiscriminate reclamation of pastures appeared in pastoral areas, resulting in the rapid development of desertification of pastures. Due to the serious wind erosion, after the reclamation of the desert area, the yield can still maintain twenty or thirty kilograms in the first two years, and it is difficult to recover even the seeds later, so it is only to abandon the cultivation and open up a new piece of land, which leads to "one acre of wasteland and three acres of desertification". According to statistics, 1.2 million hectares of grassland have been reclaimed in Ordos alone, resulting in 1.2 million hectares of grassland desertification to varying degrees.

2) Overgrazing. Due to the overabundance of livestock, the grassland grass production is insufficient, so that many high-quality grass species cannot grow.

Desert. The seed or seed is eaten when it is ripe. In addition, like goats, which account for more than half of the total number of livestock, they are very fast, good at stripping the stems and bark of sandy shrubs, gouging grass roots, and trampling, so that the grassland produces less and less grass, forming desertified land, causing a vicious circle.

3) Unreasonable woodpicking. Historically, wood mining has been one of the important factors responsible for the formation of quicksand in irrigated oases and dryland agricultural areas in China. For example, it is estimated that a family of five needs more than 700 kilograms of firewood per year, and each household needs 5,000 kilograms if Artemisia is extracted, which is equivalent to most or all of the Artemisia oleifera produced by more than 3 hectares of fixed and semi-fixed sand dunes.

According to statistics, 200,000 hectares of Bala grassland has been desertified by the Yikezhao League alone, and you ask why there is a desert. Together, part of the earth is dry, but it is very small, and now it is not caused by human waste of water and indiscriminate logging, and if human beings do not correct it, it will not take long for the earth to become a ball of sand.

It is because of the long-term action of the wind that causes the land to desertify.

Deserts are not naturally formed, but man-made.

For example, in the United States from 1908 to 1938, due to the deforestation of more than 900 million acres, large areas of grassland were destroyed, and as a result, large areas of green space were turned into deserts.

The Soviet Union's 1954-1963 reclamation campaign severely damaged the steppes of Central Asia, bringing desert disasters instead of arable land.

The Sahara Desert has caused great harm to mankind, engulfing farmland, villages, railways, roads and other transportation facilities.

According to historical records, the ancient city of Loulan on the Silk Road in China was swallowed by the desert. At present, mankind is doing everything possible to prevent and control desertification, such as planting trees, planting grass and fixing sand, and setting up sand barriers, all of which have achieved very good results.

Famous ones are the Libyan Desert, the Raibyanai Desert, the Obari Desert, the Eastern Desert and the Western Great Desert of Algeria, the Shesh Desert, the Juf Desert, the Avana Desert, the Bilma Desert, etc.

The larger area is called the "sand sea", and the sand sea is composed of complex and regular sand dunes of various sizes, with tall fixed dunes, low mobile dunes, and large areas of fixed cherry high and semi-fixed dunes.

Fixed sand dunes are mainly found in the southerly near the grassland and along the Atlantic coast. The western part of Algeria from Libby Ridge to the west is the Quicksand Zone. Shifting sand dunes are constantly moving downwind. In the Sahara Desert, a record of 9 metres of movement of mobile dunes has been observed.

The desert is terrible for the following reasons:

1. The desert has a continuous high temperature, and the desert will cause a large amount of water to flow and lose in the continuous high temperature, resulting in shock in the human body;

2. There is underflowing sand in the desert, and the underflowing sand in the desert is very hidden and almost impossible to find, once it falls into the quicksand, it will suffocate people and die;

3. There are highly poisonous desert scorpions and rattlesnakes in the desert, once you are not careful to be injured by desert scorpions or rattlesnakes, you will be poisoned and lead to death;

4. The desert is vast, once you get lost in the desert, you will be covered by the desert;

5. The large temperature difference between day and night in the desert will make people's body temperature regulation unbalanced and lead to various diseases.

Many people are curious about why there is so much sand in the desert? Deserts cover about one-third of the earth's surface, and the weather in deserts is particularly arid, so why does the desert have sand, let's take a look.

First of all, many deserts on Earth are located behind high mountains or in basins surrounded by mountains. The former is the Nevada Desert behind the Rocky Mountains in the United States, the latter in the Taklamakan Desert in China and the Gurbantunggut Desert in the Junggar Basin. These desert sands have a common feature – they are closely related to the nearby or surrounding high mountains.

Second, some deserts can form deserts without high mountains, such as the Horqin Sandy Land in Inner Mongolia, China. The sources of sand in these areas are closely related to the fluvial action of geological time. If an area is located on a large alluvial plain formed in geological time, and the climate happens to be in an arid region, then under the action of long-term winds, the material that makes up the alluvial plain will be classified, so that more and more sand will accumulate on the surface to form a desert.

Thirdly, in geological time, some deserts were neither behind high mountains nor on large alluvial plains, so what about the sand of the deserts above? It is known that during geological time there were rocks that were mainly composed of sand, such as sandstone. The physical weathering of sandstone can easily produce fine sand.

In the Ordos Plateau of China, Cretaceous dune rocks are widely distributed. It is believed that the sand in the Mu Us Desert of the Ordos Plateau was weathered by the rocks of the sand dunes of the Early Cretaceous.

Fourth, deserts are also found on the west coast of the continent near the Tropic of Cancer and the Tropic of Capricorn, forming coastal deserts such as the Atacama Desert in South America and the Namibe Desert in Africa. Desert formation in these areas is influenced by land, ocean currents, and weather systems. The climate is extremely arid, and the sand sources of the coastal desert are related to the long-term erosion of the bedrock coast by waves and the physical weathering of the local bedrock.

The above is about why there is sand in the desert, in the final analysis, the final ** of sand is related to the detrital material produced by the crushing of rocks on the earth, I hope the above content can help everyone.