Essay About Earthquakes As Main Topic For Humanity
Today, our team of professional writers wants to tell about such natural disaster as earthquake. Our planet changes every day thanks to internal processes, which permanently occur deeply in the Earth. These changes are most often slow and gradual. Precise measurements show that some places of the Earth’s surface rise, while others fall. Even the distances between the continents do not remain consistent. Vast areas, many densely populated areas and even entire countries such as Japan are under the threat of earthquakes. The greatest danger of earthquakes is in their suddenness and inevitability. However, scientific advances of recent years offer real opportunities not only to predict earthquakes, but also influence their course. It will be discovered about the reasons, mechanism of earthquake’s appearance and methods of its prediction in this essay about earthquakes.
Earthquakes are an important part of our environment and it cannot be rightly considered that any region of world is “free” of them. Seismologists work in all developed and many developing countries. They are interested in reasons of earthquake’s appearance and its mechanism. By studying the waves, which pass through the Earth during earthquakes, scientists recreate the essential details of the Earth’s internal structure. Techniques, which were developed for such study, have proven useful also in search of oil and other minerals. Important social and economical problems usually take place in countries, where earthquakes occur frequently. Therefore, engineers and architects should solve specific tasks. Thus, seismology serves as practical activity of human and also the knowledge of fundamental laws of nature.
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Ancient And Modern Explanations of Earthquake’s Cause
In searches of earthquakes’ causes, Aristotle addressed to the bowels of Earth. He believed that atmospheric vortices intruded into the ground full of voids and cracks. He thought that fire enhanced the vortices and they looked for a way out. Thus they caused earthquakes and sometimes volcanic eruptions. These ideas had existed for many years, even in spite of the fact that he did not provide any arguments in favor of his hypothesis and simply gave vent for his rough fantasy. An interesting similarity observed about the causes of earthquakes in the mythology of different nationalities. It was considered that huge animal, hidden deeply in the earth caused earthquakes. The ancient Indians considered that elephant was the cause of earthquakes while Dayaks of Sumatra considered that huge ox caused them. Earthquakes were often regarded as punishment, which was sent down by the angry gods. In Greek mythology, angry Poseidon, lord of the seas, caused the earthquakes. In Europe of 18-th century, clergy tried to inculcate the moralistic view of earthquake to the people.
However, it will be examined also modern explanations of earthquake’s cause in this earthquake essay. The science about earthquakes, seismology is although young, but made substantial progress in the knowledge of its object of study. At the cost of efforts of several researchers’ generations, specialists know very well now, what happens during the earthquake and how it manifests on the surface of Earth. Nevertheless, superficial phenomena are the result of those things, which happen in the debts. Attention of specialists focuses now on the knowledge of underlying processes in the bowels of Earth, processes, which lead, accompany and follow after the earthquake.
The theory of earthquakes as geophysical process is still in development. Although, physical and mathematical modeling is widely used in studies of such kind, knowledge of various natural phenomena associated with earthquake is largely based on the observations on the Earth’s surface. Science geology made the correct conclusions that mainly young places of the Earth’s surface are shaken. In the second half of 19-th century a scientific statement was selected, according to which ground was divided into the ancient mountain formations and growing dynamic mountain structures. It turned out that growing mountain ranges – the Alps, Pyrenees, Carpathians, Himalayas and Andes are the areas of powerful earthquakes while ancient shields (Bohemian massif) are the areas, where powerful earthquakes are absent.
Explanations of earthquakes’ occurrence will appear understandable once we consider that our planet is always in movement and these movements mainly happen in key core of Earth-lithosphere. The thickness of crust is influenced on many factors. The thickness is above 35 km under the continents at that deep “roots” almost always accompany big mountains, which are higher than degree of the ground’s subsoil. It turns out that thickness of horst in Tibet is more than 70 km. Forces act under the lithosphere that impel the structures surpass at a speed, generally, couple of centimeters per year. It is not understandable how to explain the reason of plates’ movement. For example, gradual currents of hot plastic substance in surface can cause underlying forces. These currents are the result of thermal convection in conjunction with the dynamic effects of the Earth’s rotating. In some areas, new substance rises to the top from ground’s subsoil, pushing structures apart (this happens in Mid Atlantic Ridge); elsewhere glides one by the other (as along San Andreas Fault in California). There are areas, which are called as subduction zones, where one plate after the collision pushes for another (for example, in the ocean off the west coast of South and Central America, off the coast of Alaska and Japan). Permanent movement of plates in any direction makes stone stratum to fissure, thus creating earthquakes. Earthquakes, which are caused by the movement of plates, have name of tectonic earth tremors. Although such earthquakes usually appear on the borders of structures, a small fraction of them occurs within them. Other earthquakes, such as on the Hawaiian Islands, have volcanic and human origin (filling the reservoirs, pumping water into wells, mining operations and large explosions) quite rarely cause such earthquakes.
Mechanism of Earthquake’s Appearance
It will be also revealed about the mechanism of earthquake’s appearance in this essay about earthquake. Orogenic, volcanic and seismic processes geographically gravitate to each other. However, they occur not simultaneously and always with different duration. In addition, special regions with only seismic activity exist. For example, many regions in Central Asia are characterized by high seismicity, but do not have any volcanoes. Volcanoes and earthquakes occur at one and the same territory, but rarely both in Kamchatka and Chile.
Many seismologists, saying about the mechanism of earthquakes, adhere to the theory of elastic release or elastic recoil. They link the occurrence of earthquake with sudden release of elastic strain’s energy. The rupture or shear of rocks with sudden rapid displacement (elastic recoil) happens in the result of extensive movements near the area of fault and accumulation of tensions reaching the value, which is marginal for the rocks’ strength. This is the way, how seismic waves occur. Thus, very slow and long-term tectonic movements during an earthquake transform in seismic movements, which differ high speed and are the result of the rapid discharge of the accumulated elastic energy. This discharge occurs in only 10-15 seconds (rare for 40-60 seconds).
Destruction of rocks in a limited area, which is located at a certain depth from the surface of the Earth, appears at the origin of earthquake. In a connection with emerged weakening the development of dislocation happens to the hearth or hypocentral part of earthquake’s area. Destruction occurs in that part, where the rock is less lasting. It may be in faults between the blocks. Due to some underlying processes individual parts of crust rise and go down. Plastic deformations occur in the earth’s crust at slow displacement.
Can We Predict Earthquakes?
The interest of government agencies in earthquake prediction is extremely high. Precise forecast of earthquakes can save human lives. Successful prediction of earthquakes is very rare because there are many unclear things about them. Nevertheless, the ability of accurate prediction is so important that many scientists, mainly in the USA, Japan and China are engaged in researches on prediction of earthquakes. A number of signs are adopted in one of the essays on earthquakes as a possible basis of the forecast. The following methods are the most reliable and important:
- Statistical methods;
- Allocation of seismically active zones, which have not long experienced an earthquake;
- Study of rapid shifts of the earth’s crust;
- Study of changes in the speed ratio of the longitudinal and transverse waves;
- Changes of the magnetic field and electrical conductivity of rocks;
- Changes in the composition of gases coming from the deep;
- Registration of precede shocks (“foreshocks”);
- Research of centers’ distribution and in time and space.
Statistical methods are simple. They are based on the analysis of seismological history of the area: data on the number, size and frequency of recurrence of earthquakes. Assuming that the seismicity of the area does not change over time, it is possible from these data to estimate the probability of future earthquakes. Statistical projections do not help to predict a particular place and a particular time of the earthquake. Thus, they are not very useful in view of prior events of security. On the other hand, they are very important for engineers who need to design structures for a period of 50-100 years of existence.
The principle of another method - the allocation of seismically active zones without earthquakes is logical. It is based on the definition in the seismically active zones of the areas, where there was not so long shocks and depletion of energy. It is there, where we can expect catastrophic earthquake. This method is verified and valid. However, it does not provide accurate forecast. It cannot call day, week or month, when an event will occur. Nevertheless, it does not mean that such studies do not matter. It will provide timely preparation in threatened areas and should be considered in all regulations for buildings and industrial facilities.
An increase of earth crust’s speed also indicates about the impending earthquake. This method of research is used in the USA, Japan. The earth’s surface rapidly rose before some earthquakes (rapidly in geological sense, with the speed of several millimeters per year), then the movements stopped and devastating earthquake occurred.
A lot of attention is paid to the method of speed ratio of the longitudinal and transverse waves. The speed of seismic waves depends on the stress state of rocks, through which the waves propagate. The speed also depends on the content of water and other physical characteristics of rocks. As changes of these physical characteristics are harbingers of earthquakes, they can also be considered as harbingers of seismic waves’ speed.
The intension of magnetic field and electrical conductivity increases before individual earthquakes. The Earth's magnetic field may experience local changes due to rock deformation and crustal movements. Special magnetometers have been developed in order to change small variations of magnetic field. These changes were observed before earthquakes in most areas of magnetometers’ installment. The most essential methods of prediction were discussed in this essay on earthquakes.
Natural disasters were always the problem of panic for humanity. Humanity feared such global disaster. You can read all information about this feeling in essay on fear. Even now, modern mankind suffers from earthquake. The era of antiquity and modern world differently told about the causes of earthquake. In common words, rapid movement of plates is the common reason of earthquakes. Fortunately, people have learned how to predict earthquakes. It was told about the most influential methods of prediction in this essay. Not all methods are saving, but it can be rightly considered that humanity made a big step in problem of earthquakes.