What is Tsunami
A tsunami is a sequence of long and high waves generated when there is water disruption in the ocean. The disturbance can originate from different sources such as meteorites, volcanic eruptions, landslides, and earthquakes in the sea (“How a tsunami wave works,” para 1). However, the common causes of tsunamis are earthquakes or volcanic activities. A tsunami differs from normal underwater flow because these current flows occur due to the gravitational force between the sun and moon that results in tides. Additionally, tsunamis are not like tides because they have an extended wavelength. This paper explains what causes a tsunami and how the whole process occurs.
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Understanding how earthquakes occur requires knowledge about plate tectonics. These are huge plates that form the top layer of the earth. On the seafloor, there are two plates’ asthenosphere and lithosphere that are in constant motion towards each other. These plates move at a speed of 2 to 4 inches annually (Valdes par. 3). Their movement occurs along the fault line, and they are the ones that cause earthquakes or volcanic eruptions.
The meeting point of the two plates is referred to as the plate boundary. When the plates move towards each other, the heavier one can slip under the lighter one through a process known as subduction (Valdes par. 4). When subduction occurs underwater, there are deep trenches left along the seafloor. The lighter plate is lifted abruptly as, the heavier plate sinks, causing the ocean floor to tremble. The center of the earthquake is where the first rocks are broken to generate the first seismic waves. When the two plates snap, tons of rocks are thrown up with a lot of force. This force also pushes the water above sea level, forming the first wave of a tsunami.
Hitting the Water
When water is pushed upwards, it is acted upon by the gravitational force that further pushes the energy in the water parallel to the sea level. The energy then moves through the deep sea, going far from the initial point of disturbance. The force that is created by the seismic vibrations gives the tsunami unbelievable speed. The real speed of the waves is calculated by multiplying the depth of the water with gravitational acceleration. Stud reveals that water waves can even travel at a speed of 800 kilometers per hour; this is almost the speed of a jet. The ability of the tsunami to maintain its high speed is determined by the depth of the sea (Valdes par. 6). Therefore, the speed is high in deep water than in shallow water.
As the wave approaches the coastline, it decreases in speed to almost 50 km per hour. Since the other part of the wave left behind is still traveling at high speed in the deep sea, it approaches the front very fast, causing water traffic jams in the ocean (Iswadi 38). The water now needs some space to occupy, so it raises, creating a wave of 15, 25, or even 40 meters in height (Yoshida 185). This is due to the increasing compression caused by water from the part of the wave left behind (Yoshida 185). This water wall finally lands at the coast at a speed of 30 to 50 km/hr and causes a lot of destruction.
It is observed that before a tsunami hits, the water level on the cost shore drops. A person observing at the beach will notice the falling and rising of the water. Sometimes, water might drain away completely. This is followed by the tough of the tsunami wave that arrives first (Valdes par. 7). The wave works just like a tide, such that it goes out and then comes in. Similarly, as the tsunami nears the coastline, water goes away from the beach; this occurs to feed the wave effect. “The wave of a tsunami is short enough to have a fast effect in minutes, but long to carry a lot of energy” (Maximiliano 372). Hence, tsunamis have nothing special; they are just like normal waves. However, their features and impacts are overwhelming. When water drains at the beach after the first wave hits, people are advised to avoid entering the beach because there are still other waves coming (Maximiliano 372).
Therefore, people should stay at a distance of about 1.5 kilometers away from the coast shore to avoid the waters.
as little as 3 hours
Tsunamis are powerful and can cause death and massive destruction of property. Previously research reveals that tsunamis have killed more than 100,000 people (“How a tsunami wave works,” par. 3). For instance, in 1992 and 1993, several tsunamis hit Japan, Indonesia, and Nicaragua with a combined death rate of more than 5,000 (“How a tsunami wave works,” par. 3). An earthquake happened on July 17, 1998, off the coast of Papua New Guinea, producing three waves of about 9 to 12 meters high. The wave inhabited many villages around the island and killing many people and leaving thousands of them homeless and with injuries.
“How A Tsunami Wave Works | National Oceanography Centre.” Noc.ac.uk. N.p., 2021. Web.
Iswadi. “Acehnese literature post-conflict and tsunami: between the reflection of humanity and political cleanser.” Proceedings of EEIC 2 (2019): 37-41.
Maximiliano, Oportus. “Ex post analysis of engineered tsunami mitigation measures in the town of Dichato, Chile.” Natural Hazards 103.1 (2020): 367-406.
Valdes, Robert, Nathan, and Lamb. “How Tsunamis works.” HowStuffWorks. N.p., 2021. Web.
Yoshida, Keisuke. “Estimation of hydrodynamic forces acting on concrete blocks of toe protection works for coastal dikes by tsunami overflows.” Applied Ocean Research 80 (2018): 181-196.