An earthquake is one of the natural phenomena that occur on the planet that used to be intimidating events of sacred significance for people in the ancient times. The current scientific studies in the field of seismology apply advanced technologies and knowledge to explain the physical changes and movements in the crust related to earthquakes. These efforts are necessary because earthquakes are considered to be among the most dangerous phenomena associated with massive destruction, and they cannot be controlled. For this reason, scientists try to evaluate the matter from different angles and establish the ways to avoid damage when it is possible. The current paper describes the main causes and most common effects of earthquakes.
In order to discuss the present subject, it is important to define the main notion. Earthquakes are described as the energy suddenly released in the mantle or crust that creates vibrations of different sizes and continuance of a local character. The nature of earthquakes was described from a scientific point of view only in the nineteenth century. However, not all reasons of earthquakes have been determined. For example, according to Robert Mallet, the founder of seismology, earthquakes are results of subterranean explosions. In his work, published in 1862, Mallet covered the Basilicata earthquake, but he lacked information to describe the phenomena and its causes. Later, another scientist, Rudolph Hoernes, made an effort to classify earthquakes according to the natural forces due to which they emerge. Therefore, earthquakes are classified into the following three main types: earthquakes that occur due to the collapse of the roofs of cavities within the earth’s crust, earthquakes that appear when volcanic eruptions lead to explosions, and earthquakes that arise because of the crustal movements of the fault planes. A fault plane is the surface where blocks of the earth slip. A fault block is usually moved by gravity, and it may sink between other faults. As a result of such movement, a topography of a place changes, and may it may be easily recognized by mountain ranges. For example, crustal movements are common for the North American Basin.
The movement of plates is the most common cause of earthquakes. Plates can move differently; for instance, they may pass each other. For instance, such activity is typical for the California region. On the western coast of America, earthquakes emerge because of the movement of plates that overrun each other. This type of movement is also regarded to as tectonic movement. In addition, volcanic activity leads to earthquakes as well (for example, the Krakatoa volcanic eruption). Moreover, the contraction and expansion of gases under pressure may cause earthquakes. The reasons mentioned above are the main natural causes of this phenomenon.
The twentieth century introduced another type of earthquakes. Military activities and nuclear weapons testing that take place underground affects the earth. Thus, if a nuclear bomb explodes, it creates vibrations that lead to small local earthquakes. These earthquakes are felt within the radius of a few miles. It is easy to find the hypocenter of such earthquakes as they have a distinctive character and sound. If one country tests nuclear weapons, other countries may feel tremors that result from explosions. These earthquakes are small in comparison to natural earthquakes and do not have a similar destructive power as they do not create foreshocks and aftershocks (quakes that happen before and after the mainshock that is the largest earthquake of a sequence). It should be noted that aftershocks could occur weeks and even years after the main quake, depending on its magnitude.
In order to evaluate the effects of earthquakes and describe them, it is necessary to measure the relative size of vibrations and quakes. The energy that is released during an earthquake corresponds to the scale developed by Richter. Another scale is presented by Mercalli, who measured earthquakes by observing the destruction. Richter’s scale is logarithmic, and every next number is ten times higher than the previous one. Therefore, number one and two are used to indicate earthquakes that can only be detected by special technology, and only the people who are extremely sensitive to movements can feel them. Earthquakes that correspond to number three of the Richter’s scale are felt indoors by people, and they can be mistaken for large passing vehicles. Fourth degree earthquakes disturb trees and even crack walls. Fifth degree earthquakes affect the structure of weak buildings. When earthquakes that correspond to number five strike, people see walls collapsing and the cracking of the ground. The sixth degree reflects the power of earthquakes that are able to destroy whole structures and cause landslides. The seventh degree describes earthquakes that cause the destruction of bridges, visible waves of the surface, and force objects to move. The earthquakes with the epicenter in the sea can be even more destructive than earthquakes that occur on the surface due to tidal waves (tsunamis). Tsunamis are forceful waves that can destroy cities and bring death to people who live close to the coastline.
Apart from the destructive effects mentioned above, earthquakes may be constructive events that contribute to the development of the economies of various countries. For example, in some cases, when plates move, they may bring forward fertile layers of the ground that were hidden before. Such changes may increase crop production and create more opportunities for the agricultural industry. As it was stated before, earthquakes change topography and may create gulfs and bays, which may, for example, benefit fishing industry. Therefore, earthquakes are not entirely devastating events.
Among destructive earthquakes of the past, one of the most vivid examples is a volcano earthquake known as Krakatoa that happened in 1883.The volcano’s activity destroyed half of the mountain and produced sea waves that affected tide gauges half way around the world; air waves that traveled three times around the globe before they ceased. Such power had a negative impact on the environment and emphasized the importance of seismologic studies.
The future perspective regarding the issue of earthquakes is more optimistic. Scientists cooperate in order to develop technology that could decrease the negative consequences of earthquakes. Presently, architects around the world build earthquake-resistant structures. Seismologists help to predict earthquakes and save lives by means of evacuation. Another option is to create technology that could modify weather and control earthquakes. This opportunity is not available as of now, but it could be quite helpful if designed properly.
In conclusion, earthquakes are sudden dangerous occurrences that have mostly negative effects and may lead to loss of lives. There are a few main reasons of earthquakes. Most earthquakes occur because of the movements of plates. Other earthquakes may be caused by volcano activity. In addition, some earthquakes happen because of human activity (for example, nuclear weapon testing). Earthquakes have a negative impact on cities and town as they destroy structures and lead to fatalities. Moreover, earthquakes may change the topography of different areas. Among positive effects is the change of the ground layers, which may benefit the growth of crops. In some cases, new bays appear that allow to lead fishing activities. Earthquakes require further research and studies.
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