Causes of sandstorms, tsunamis and earthquakes

Modern science explains the causes of earthquakes as follows:

Because the earth is constantly moving and changing, it gradually accumulates huge energy, causing sudden rupture of rock strata or dislocation of original faults in some fragile areas of the crust. This is an earthquake.

Most earthquakes occur in the earth's crust.

Earthquakes are divided into tectonic earthquakes, volcanic earthquakes, subsidence earthquakes and induced earthquakes.

Tectonic earthquake refers to that under the action of tectonic movement, when the local stress reaches and exceeds the strength limit of rock stratum, the rock stratum will suddenly deform or even rupture, and the energy will burst out at once.

Tsunami refers to the huge waves of hundreds of kilometers caused by submarine earthquakes, volcanic eruptions, underwater landslides and collapses. Its performance in coastal areas is that the sea water rises sharply, suddenly forming a "water wall", which, accompanied by rumbling noise, instantly invades coastal land, engulfs fertile fields and towns, and then the sea water suddenly recedes, or rises first and retreats, and sometimes appears repeatedly, causing huge loss of life and property. Before the arrival of tsunami waves, local tsunamis are often accompanied by strong earthquakes or earthquake disasters. China is also a country with frequent storm surges. The tide level anomalies expressed by storm surges, earthquakes and tsunamis have been called tsunamis, sea overflows or great tsunamis in past dynasties. In recent 20 years, Chinese academic circles have decided to call the tidal level anomalies caused by storms and earthquakes storm surges and tsunamis respectively. In addition, sometimes disasters caused by astronomical, storm, earthquake and other abnormal tidal levels are collectively referred to as "tidal disasters". But in most cases, the so-called tidal disaster is customarily referred to as storm surge disaster. The initial elevation of the water surface near the tsunami source in the ocean is only 1 to 2 meters. When this wave moves in the deep sea, the wavelength can reach tens to hundreds of kilometers, the period can reach 200 minutes, and the most common thing is that it can reach the speed of nearly 1000 kilometers per hour. Therefore, the tsunami will not cause disaster in the deep sea, and it is even difficult to detect such fluctuations. However, when the tsunami wave enters the continental shelf, its depth becomes shallow sharply and its energy is concentrated, resulting in its amplitude increasing. If the continental shelf is very narrow, tsunami waves with almost the same speed from the sea surface to the seabed will carry huge energy to the shore or harbor, and the wave height will suddenly increase. At this time, there may be a huge wave with an amplitude of 20-30 meters, which will cause the peak to roll back. This huge wave rushed there, and it was in ruins. It is in these places that the tsunami has become the greatest threat to life and a terrible natural phenomenon.

Relevant research points out that the formation of sandstorms must meet four conditions: first, the dust on the ground is the material basis for the formation of sandstorms; The second is strong wind, which is the dynamic basis of sandstorm formation and the dynamic guarantee of sandstorm long-distance transportation; Thirdly, the unstable air state is an important local thermal condition, and sandstorms often occur in the afternoon and evening, which shows the importance of local thermal conditions; Fourthly, in the arid climate, sandstorms mostly occur in northern spring, which is a good evidence that sandstorms will not occur for a period of time after rainfall. In the desert fringe in spring, due to long-term drought, there is little vegetation coverage on the surface, and when there is strong wind, the dust on the surface is easily blown up and transported away. However, due to the large particle size of sand, it is not easy to form suspension movement (suspension movement is a necessary condition for small particles to ensure long-distance transportation), so it can not be transported over a long distance, which is also the main reason why there is only dust and little sand blowing in areas far away from dust. If the gale lasts for a long time, the suspended floating dust can be transported far away, and sandstorms will appear in the passing areas; When the wind speed decreases to a certain extent, the floating dust will fall, and there will be dust-falling weather in the local area. If it rains at this time, the so-called "mud rain" will form.

According to the four conditions required for the formation of sandstorms, the loess plateau, the vast desert and the land destroyed by human factors in the process of desertification, the land reclaimed in late spring in the north and the infrastructure under construction (such as roads) provide sufficient material sources for the occurrence of sandstorms; In spring, the drought in the northern region increases the possibility of sandstorms; The generation of gale is a complex atmospheric phenomenon, which is mainly the result of cold front activity or the adjustment of latitude and longitude circulation. It can be seen that the occurrence of sandstorm is the result of the joint action of many complex factors. The destruction of nature by human activities leads to the intensification of land desertification, which plays an extremely important role in the occurrence of sandstorms. In recent years, global drought and other abnormal weather phenomena have also played an inestimable role in the occurrence of sandstorms. Therefore, human activities only play a certain role in the production of sandstorms, and it cannot be said that sandstorms are caused by human factors.