Desert, mainly refers to the barren areas where the ground is completely covered by sand, the vegetation is very sparse, the rain is scarce, and the air is dry. Deserts are also called "sand curtains", which are areas of drought and water shortages and few plants. Desert areas are mostly sandy beaches or dunes, and rocks under the sand often appear. Some deserts are salt flats, completely devoid of vegetation. Deserts are generally aeolian landforms. There are sometimes valuable deposits in the desert, and many oil deposits have been discovered in recent times. Deserts have few inhabitants, and resource development is relatively easy. The desert has a dry climate, and it is also a happy home for archaeologists, where many human relics and earlier fossils can be found.
1.Overgrazing Due to excessive grazing by local herdsmen, the supply of grassland production is insufficient, so that many high-quality grass seeds are eaten before they can grow into seeds or when the seeds are mature. In addition, like goats, which account for more than half of the total number of livestock, they move very quickly, and are good at peeling off the bark of sandy shrubs, shaving grass roots, and trampling, making the grassland production less and less, forming desertified land, and creating a vicious circle.
2.Unreasonable woodcutter picking
Main use: firewood
2.Classification
Most desert classifications are based on rainfall days per year, total rainfall, temperature, and humidity. In 1953, Peveril Meigs divided the dry areas on the earth into three categories: the extra-dry areas are areas with no vegetation at all (annual precipitation below 100mm, no rainfall throughout the year, no periodic rainfall), and its area accounts for 4.2% of the global land area. %; Dry area refers to the area with seasonal grass but no trees (evaporation is larger than precipitation, annual precipitation is below 250mm), its area accounts for 14.6% of the global land; semi-dry area has 250-500 mm Rain, is a zone where grass and low trees can grow. The extra-dry and dry areas are called deserts, and the semi-dry areas are called steppes.
1.Tradewinds Desert
Trade winds are winds that emanate from the subtropical high pressure and converge toward the equatorial low pressure area. The dry trade winds dissipated the clouds, allowing more sunlight to heat the land. The Sahara Desert, the largest desert in the world, is mainly formed by the action of the hot and dry trade wind (locally known as the Hamadan wind), and the temperature during the day can reach 57°C.
2.Mid-latitude deserts
Mid-latitude deserts (or temperate deserts, see Temperate desert climates) are located between 30° and 50° latitude. The Sonoran Desert in southwestern North America and the Tengger Desert in China are both mid-latitude deserts.
3.Rain Shadow Desert
Rain Shadow Desert is a desert on the edge of mountains. Because the mountain is so high, it creates a rain shadow effect, forming a desert in the leeward side of the mountain.
4.Coastal deserts
Coastal deserts are generally located on the west coast of the mainland near the Tropic of Cancer and the Tropic of Cancer. Due to the passing of cold currents, the temperature and humidity are lowered, and there is a lot of fog in winter, which blocks the sun. The reasons for the formation of coastal deserts are: land influence, ocean influence and weather system influence. The Atacama Desert, a coastal desert in South America, is the driest desert in the world, and it often rains more than 1 mm every 5 to 20 years. The Namib Desert in Africa has many crescent-shaped dunes and is often windy.
5.Ancient deserts
Geoarchaeologists have found that the Earth's climate has changed a lot, with periods in geological history drier than it is now. 12,500 years ago, about 10% of the terrestrial deserts between 30°N and 30°S latitude were widespread. 18,000 years ago, 50% of this area was desert, including what is now tropical rainforest. Fossils deposited in deserts have been found in many places, and the oldest is 500 million years old. The Nebraska Sand Hills in the United States are the largest ancient sand seas in the Western Hemisphere. It now has an average annual precipitation of 500 mm, the sand has been stabilized by vegetation, but dunes up to 120 meters can still be seen. The Kalahari Desert is also an ancient desert.
6.Saline desert
All kinds of saline-alkali soils are formed under certain natural conditions, and the essence of the formation is mainly the redistribution of various soluble salts in the horizontal and vertical directions on the ground, so that the salt gradually accumulates on the soil surface of the salt-collecting area. Accumulate, such as UAE, etc.
7.Alien Desert
Mars is the only non-Earth planet in the solar system that has been found to have wind shaped landforms, and there are sand dunes on Mars. But if you just look at dryness, almost all alien celestial bodies discovered now are covered in "deserts".
Deserts pose major challenges to the living environment of human beings, mainly including land degradation, biological community decline, climate deterioration, destruction of living facilities and construction projects, and serious environmental pollution. Therefore, controlling sandstorm hazards and preventing desertification are closely related to human survival and development.
