Quicksand is simply sand that can flow like a liquid, that is, sand that can flow. This is a natural phenomenon. It often appears in the desert with unstable foundation. When a heavy object is placed on the sand, it will sink to the bottom like the bottom.

Formation principle

Once the surface of quicksand is disturbed, it will "liquefy"

Bourne of the University of Amsterdam in the Netherlands met a local shepherd while on vacation in Iran. Pointing to quicksand, he told Bowen that once a camel sank in the village and disappeared immediately. Bern was skeptical about this and immediately studied it after returning to China. He carefully watched and analyzed dozens of movies describing the scene of quicksand eating people, and found that the descriptions of quicksand in these movies were simply full of mistakes. Later, Bourne mixed fine sand, clay and salt water in the laboratory and reconstructed a miniature indoor quicksand model for research.

After repeated experiments, researchers led by Berne found that it takes several days to make sand as sticky as toffee, but it is easy to lose its viscosity as long as proper pressure is applied to its surface. Once the surface of quicksand is disturbed by movement, it will "liquefy" quickly, the sand on the surface will become loose and soft, and the shallow sand will flow down quickly. This migration sinks objects moving on quicksand. However, with the increase of sinking depth, the sand and clay falling from the upper layer to the bottom layer gradually gather, which will form a thick sediment layer, which will increase the viscosity of the sand rapidly and prevent the object from sinking further.

Objects whose density is less than quicksand will float on quicksand.

It is also found that when an object sinks into quicksand, the sinking speed depends on the density of the object itself. The density of quicksand is generally 2g/ml, while that of human is 1g/ml. At this density, the human body will not be destroyed when it sinks into quicksand, and it will often stop when it sinks to the waist. The researchers also found that even some objects whose density is much higher than quicksand can float on quicksand. In the experiment, the researchers put an aluminum basin with a density of 2.7 g/ml on top of quicksand. Although its density is higher than that of quicksand, it can still stay on the surface of quicksand calmly because of its buoyancy and surface tension. The situation changed when scientists began to gently shake the aluminum container. The container is a little heavy. When they shook hard, the container slowly sank to the bottom of the sand.

It takes the strength to lift a car to pull your feet out of quicksand.

It is believed that people trapped in quicksand can't move generally, and the sand with increased density sticks to the lower body of the human body falling into quicksand, which causes great pressure on the human body and makes it difficult for people to make efforts. Even Hercules can hardly drag the trapped people out of quicksand at once. According to the researchers' calculation, it takes about 654.38+ million newtons to pull out a trapped person's foot at a speed of one centimeter per second, which is about the same as the force to lift a medium-sized car. So unless there is a crane to help, it is difficult to pull people out of quicksand at once. The study also pointed out that according to the calculation of this force, if you pull hard, the human body will be torn off by powerful force before the quicksand "lets go". The danger caused by this move is much higher than letting him temporarily stop in quicksand.

The quicksand samples taken from the Sahara desert are semi-solid composed of sand and salt water, and these particles are loosely packed together. The accumulation of sand makes it have a seemingly stable surface, but even with a small pressure, the whole framework of quicksand will collapse immediately. Thick "mortar" accumulates at the bottom, which can stick to all objects and make them unable to move; Ultrafine particles in quicksand are more dangerous-it makes quicksand have great clamping force and can kill people.

If you are caught in quicksand, the wisest thing to do is not to struggle in quicksand, but to pour your feet back and forth patiently and slightly, so that the "mortar" will loosen and not stick to you tightly. If the camel was indeed swallowed by the quicksand in the Sahara desert, Bonn thought that the camel must have struggled to escape, and the result was completely submerged by the quicksand.

Sandstorm is a general term for sandstorm and sandstorm. It refers to a severe sandstorm weather phenomenon in which strong winds blow and drag a large amount of sand and dust on the ground into the air, making the air particularly turbid and the horizontal visibility less than one kilometer. Among them, sandstorm refers to a sand-laden storm formed by strong winds blowing a large number of sand near the ground; Sandstorm is a storm formed by strong winds, which brings a lot of dust and other particles into the sky.

Formation condition

The weather situation favorable to strong winds or strong winds, favorable distribution of dust sources and favorable air instability conditions are the main reasons for the formation of sandstorms or strong sandstorms. Strong wind is the driving force of sandstorm, and the source of sandstorm is the material basis of sandstorm. Unstable thermal conditions are conducive to the increase of wind power and the development of strong convection, thus carrying more dust and winding it higher.

In addition, drought and lack of rain in the early stage, warming weather and rising temperature are the special weather and climate background for the formation of sandstorms; The convective cells before the ground cold front develop into clouds or squall lines, which is a small and medium-sized system conducive to the development and strengthening of sandstorms. The topographic condition conducive to the increase of wind speed, that is, the narrow tube effect, is one of the favorable conditions for the formation of sandstorms.

The main component of soil and yellow sand is silicate. When there is less rain and the temperature gets warmer, the silicic acid on the silicate surface loses water.

In this way, the surface of silicate soil micelles and sand particles will be negatively charged and repel each other, becoming aerosols that cannot be aggregated together, thus forming sand blowing, that is, sandstorms. Sandstorms are essentially silicate aerosols with negative charges.

In short, the formation of sandstorms requires these three conditions:

One is the dust on the ground. It is the material basis for the formation of sandstorms.

The second is the strong wind. This is the dynamic basis for the formation of sandstorms and the dynamic guarantee for the long-distance transportation of sandstorms.

Third, the air state is unstable. This is an important local thermal condition. Sandstorms often occur in the afternoon and evening, which shows the importance of local thermal conditions.

Mirage, referred to as mirage for short, is a natural phenomenon formed by refraction and total reflection of light, and a virtual image formed by refraction of light reflected by objects on the earth through the atmosphere.

Formation condition

Mirages are closely related to the geographical location, geophysical conditions and meteorological characteristics of those places at a specific time. The abnormal distribution of temperature is the meteorological condition for the formation of most mirage.

As far as the formation of taking down the slug is concerned. In summer, when the sun burns in the desert, the sand is burnt. Because of the small specific heat of sand, the temperature of low-level air near sand rises rapidly, while the temperature of high-level air is still very low, thus forming an abnormal distribution of temperature. Due to thermal expansion and contraction, the density of hot air in the lower layer near the sand is small, and the density of cold air in the upper layer is large, so that the refractive index of air is small and the air in the upper layer is large. When the light reflected by a distant higher object enters the sparse air in the lower layer from the dense air in the upper layer, it is constantly refracted, and its incident angle gradually increases, which is equal to the critical angle, and total reflection occurs. At this time, if people look against the reflected light, they will see the cockroaches below.

Because of the dark color of asphalt pavement, it has strong absorption ability in the hot summer sun, and it will also form the distribution characteristics of cold and dense upper air and hot and dense lower air, so it will also form underflow.

A mirage in the desert is a refraction phenomenon when sunlight meets air with different densities. In the desert, the sand is baked by the sun during the day, and the temperature on the surface of the sand layer rises rapidly. Due to the poor heat transfer performance of air, when there is no wind, the vertical temperature difference over the desert is very significant, with high air density in the upper layer and low air density in the lower layer. When sunlight enters the low-density air layer from the high-density air layer, the speed of light changes, and after the refraction of light, the oasis in the distance appears in front of people. On the sea or river, this kind of "mirage" phenomenon happens from time to time.

A mirage is an optical illusion, a virtual image formed by the refraction of light reflected by objects on the earth through the atmosphere. Phantom is a mirage for short. According to the principle of physics, a mirage is because different air layers have different densities, and the refractive index of light in air with different densities is different. That is, because the density between the cold air on the sea surface and the warm air at high altitude is different, the light is refracted.