Beijing time on January 14, according tomedia reports, when people mention the concept of “desert”, most people will think of the Sahara desert ups and downs of sand dunes, the flow of sand dunes to the bottom of the eye. This is the concept of desert described by movies, television shows and popular culture, but it is not. It is true that there is a lot of sand in the deserts of the world, but this raises the question: What is under the golden sand carpet?
In fact, most deserts on Earth are not covered by sand, but by exposed bedrock and desert rock, depending largely on the surrounding terrain, geological formations, and climate patterns.
By the official definition, deserts are characterized by extreme lack of precipitation, and the main reason for the low rainfall is being on the “opposite side of the mountain”, and to understand this, it is important to consider changes in air and water vapor when encountering obstacles. For example, a flow of air from the west, blocked by the north-south toward the mountains, moist, warm air will roll to the bottom of the mountain range, forming a gradual rise to form a cloud, when the air rises, began to cool, in the form of precipitation to release water.
When the air moves to the top of the mountain range, there is essentially no moisture, and there is not much precipitation except for a few clouds, and the east side of the mountain is called a “rain shadow zone” where the air sinks and warms up, but there is no moisture to form. This usually leads to dry and hot winds, which can exacerbate desert formation for thousands or millions of years.
This means that some deserts are not located near mountains, but are the result of unique climate patterns within the mountain region, with high-pressure systems filled with warm, heavy air that cannot rise, cool, and create clouds in subtropical and semi-permanent high-pressure systems, such as the Sahara. In addition, if a high-pressure system is very strong and stable, it will make it difficult for the low-pressure system to move, produce changes in climate patterns, and ultimately, the region has little rainfall and is hit by dry winds and does not benefit from cold front movements.
Although most deserts are characterized by hot, there are also deserts with cold climates, such as the Gobi Desert, the coastal deserts of Antarctica, Peru and northern Chile, where the air is cold and cannot be hydrated and produces precipitation, and although the surface of the Antarctic desert is snow and ice, ice crystals and dry winds create similar conditions. White storms have replaced traditional desert sandstorms.
Over millions of years, these particular climate patterns and topographical factors have left the land virtually free of vegetation, as very little water tends to survive and changing terrain makes it difficult for plant roots to take root and grow. These desert areas are also susceptible to temperature changes because they are easily accessible and lose heat, and unlike cities, jungles and grasslands, sand in the desert does not maintain heat efficiently, so while the day can be very hot, the ground cannot hold it until night, causing temperatures to fluctuate dramatically. This is another obstacle to the prosperity of life.
Where does the sand come from?
While we partly refute the idea that the desert is completely covered with sand, the question is where did the sand come from in the first place? As mentioned earlier, sharp changes in the temperature difference between day and night can cause stress to rocks in an area, causing them to crack and cause fragmentation.
Combined with dry gusts, it is easy to cause erosion, in thousands of years will form a large amount of sand, sand is basically classified by particle diameter, located at the bottom of the desert sand grain diameter is larger, heavier, is a sand structure, located in the surface of the desert is fine sand, sand particles diameter is smaller, similar to silt, can be blown into sand dunes, This in turn contributes to the wind erosion process of the desert bedrock.
In fact, sand is a highly abrasive substance, as the wind blows fine sand onto the rock, some unique structures of the bedrock and exposed rock will be subjecttous by sand wind erosion shape, sand sea is in a changing landscape, shaped by the wind into a variety of recognizable shapes and structures, they can fluctuate over several years.
In short, deserts are not made entirely of sand, but also include sand-based deserts, pebble-dominated deserts, rocky deserts, each type of desert with unique erosion patterns and climatic characteristics. Some deserts are characterized by sand and sand dunes, while some desert areas are barren and barren.
What’s under the sand?
Now that people know where the sand comes from and how the desert is formed, one might guess what is beneath the sand layer. About 80 per cent of the desert is not covered by sand, but rather exposes the bare land below – the bedrock and cracked clay of the dry ecosystem, the area where there is no soil cover and no vegetation to keep the soil, and the desert rock is completely exposed and eroded by wind and sand.
Deserts must not be flat, hills and rock formations are either weathered into flat ground at the bottom of the desert or eroded into residual rocks, depending on the type, color, and hardness of the rocks on the surface of the desert. In addition, as the desert continues to “grow”, the sand layer is not gradually expanding outwards, but the desert edge of the ecosystem gradually desertification, the original soil is blown away by the wind and sand, vegetation reduction can not fix the soil, a large amount of water loss, geological structure suffered from wind and sand erosion.