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A tsunami is a destructive natural disaster that can result
in the loss of lives and property. It is a series of long, high waves that
are generated when there is a disturbance in the ocean's water. The
disruption can come from various sources, including meteorites, volcanic
eruptions, landslides, and earthquakes in the sea. Tsunamis differ from
normal underwater flow because they have an extended wavelength and can be
caused by various factors. This article will explain what causes tsunamis
and how the entire process occurs.
To understand the cause of tsunamis, it is essential to have knowledge about
plate tectonics, which are huge plates that form the top layer of the earth.
Two plates on the seafloor, the asthenosphere, and lithosphere, are in
constant motion towards each other, moving at a speed of 2 to 4 inches
annually. Their movement occurs along the fault line, which can cause
earthquakes or volcanic eruptions.
The meeting point of the two plates is known 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. When subduction occurs
underwater, deep trenches are left along the seafloor. The lighter plate is
lifted abruptly, 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.
When the 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 incredible speed. The real speed of the waves is calculated by
multiplying the depth of the water with gravitational acceleration. Studies
reveal that water waves can even travel at a speed of 800 kilometers per
hour, which 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. 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. The water now needs some space to occupy, so it
raises, creating a wave of 15, 25, or even 40 meters in height. This is due
to the increasing compression caused by water from the part of the wave left
behind. This water wall finally lands at the coast at a speed of 30 to 50
km/hr and causes a lot of destruction.
Before a tsunami hits, the water level on the coast 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 touch
of the tsunami wave that arrives first. 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. Tsunamis have nothing special; they are just like normal waves. |
