Tsunami and Process of Its Occurrence
Natural disasters, which cause large-scale destruction, are quite often localized. Because of this, some natural phenomena can be poorly studied since they do not exist in the sphere of some people’s habitation. This category of cataclysms includes tsunamis, which can occur only near the coastline and when several conditions coincide. However, because of this, a collision with them becomes more dangerous since an unprepared person will not respond correctly. Simultaneously, tourism development made it possible for people to get into an unfamiliar and potentially dangerous environment. Thus, studying various natural phenomena and the mechanisms of their work is necessary and allows a person to prepare for a sudden encounter. The purpose of this paper is to develop this thesis through the process of scientific analysis of the process of tsunami occurrence since this phenomenon best fits into the category of dangerous but extremely specific cataclysms.
A tsunami has several specific characteristics that distinguish it from other similar phenomena. First, it can only occur at the coastline, which is hinted at by the name itself, borrowed from the Japanese language and meaning “coastal wave” (Tsunami). Accordingly, regions located close to water suffer most from it. Secondly, the reasons for the occurrence of this phenomenon are extremely specific. Most tsunami occurs in the so-called Ring of Fire in the Pacific Ocean due to the peculiarities of tectonic activity (What Causes a Tsunami?). Finally, in forecasting and determining tsunamis, one has to rely heavily on indirect methods. In turn, this leads to difficulties in alerting the population. It is all the more important to investigate the tsunami on your own.
First of all, one needs to understand that a tsunami is a series of high waves. As in the case of circles on the water, diverging from a stone thrown into a pond, an external force must be applied for a tsunami to occur (Tsunamis). Tsunamis are most often divided into three types: caused by underwater earthquakes, landslides, and volcanic eruptions (tsunamis). In addition, human activity and the fall of heavenly bodies are distinguished among the much less common causes. For example, the fall of an asteroid 66 million years ago, which caused the death of dinosaurs, also gave rise to a massive tsunami, the wave height of which reached 1.5 kilometers (Kornei). However, the tsunami propagation process almost always follows the same scenario, making it easier for ordinary people to prepare for them.
In almost all cases, the factor shaping the first waves is a change in the ocean floor’s topography. For example, due to the movement of tectonic plates, there is a sharp difference in heights at the bottom. This leads, in turn, to a sharp dip or rise in the water column, which forms divergent waves (Tsunami). However, it should be noted that most earthquakes occurring in the ocean cannot generate large enough waves. According to geological data, only earthquakes with a magnitude of 7.6 and above can be considered truly dangerous (What Is It About an Earthquake). This fact corresponds to the fact that a sharp drop in the water level is necessary for the appearance of hazardous waves. Thus, an earthquake generates a series of waves that diverge from the epicenter at a tremendous speed, reaching almost 1000 kilometers per hour (Tsunami). However, the waves still do not have a sufficiently high height and are located at a great distance from each other.
An increase in wave height occurs when they reach a gradual decrease in seabed depth closer to the shore. In this case, the speed of the waves decreases, due to which the distance between them diminishes and, at the same time, the amplitude increases. The highest waves are generated near steep banks and in wedge-shaped bays, where focusing can occur. High waves move ashore and hit them, flooding huge areas (Tsunami). One of the most dangerous moments in the context of a tsunami is the presence of more than one wave. Many people assume that after the first flooding, they are no longer in danger. Moreover, the water level often drops sharply, exposing a much larger coastal area than usual. However, since each tsunami consists of many waves, it is necessary to wait for usually several hours before returning to the areas affected by the tsunami.
Earthquakes are the overwhelming cause of this phenomenon, which is why researchers often consider them. Landslides of the seabed or volcanic eruptions occur much less frequently and practically do not have any specific features. However, two factors associated with the early signs of a tsunami are worthy of note. In the event of a landslide, the water level in the localized area decreases. Consequently, the first sign of a tsunami of this kind may be an abnormal drop in the coastal water level (Tsunami). As in the case of tsunamis due to earthquakes, this is only a sign of an impending wave. In volcanic eruptions, two options are possible: a landslide due to surface shear or contact of hot magma with cold water, which causes an explosion of steam, forming waves. In both cases, the further development of the tsunami follows the scenario already described.
Thus, the critical factor leading to almost all tsunamis is a sharp change in the bottom level. They do not pose a significant danger in the open ocean, but they gain strength, approaching shallow water and increasing in height. In addition, it must be remembered that a tsunami is a whole series of waves, so it is hazardous to go ashore after the first wave leaves. Understanding exactly how a tsunami is formed can allow a person to prepare themselves, especially when visiting shores in earthquake-prone areas.
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“Tsunamis.” National Oceanic and Atmospheric Administration, 2018, Web.
“What Causes a Tsunami?” Pacific Tsunami Museum, Web.
“What Is It About an Earthquake That Causes a Tsunami?” USGS, Web.