Tsunami waves are so destructive because of their height and energy. They are created by violent underwater seismic movements, causing waves that can reach impressive heights and crash onto the coasts with incredible force, causing considerable damage.
A tsunami often starts when a sudden underwater event displaces a huge volume of water. Typically, this happens as a result of an earthquake beneath the ocean, when a tectonic plate shifts abruptly and pushes up or down tons of water. But that's not all: a landslide, a volcanic eruption under the sea, or even the fall of a meteorite can also be responsible. From that moment on, the displaced water forms waves that move in all directions, like a series of giant ripples that quickly spread across the entire ocean. At this stage, in the open sea, tsunami waves usually remain low and spaced out — sometimes barely visible despite the colossal energy they carry. But be careful, they travel at hundreds of kilometers per hour, which explains why they sometimes reach areas very far from their origin.
Offshore, the tsunami waves are impressive not for their height, often quite low, but for the colossal amount of energy they carry. This titanic energy comes from the initial force of the underwater earthquake or other events such as underwater landslides or volcanic eruptions. At this stage, the wave speed can exceed 700 km/h, almost as fast as a commercial airplane. However, due to their long wavelength, these waves often remain imperceptible to the eye, barely manifesting at the surface. It is only as they approach the shores, when they suddenly slow down due to the rising seabed, that they truly reveal their destructive power.
When a tsunami approaches the shore, the wave encounters increasingly shallow water. As a result, the monstrous energy contained in the wave, which was dispersed over a great depth in open water, condenses into a significantly reduced height. This sudden compression of energy leads to a rapid increase in the height of the wave as the depth decreases. Essentially, it's like squeezing a hose between your fingers to increase the pressure of the water jet. This phenomenon is called shoaling. The result: an initially small wave offshore can become an immense and terrifying wall of water once it reaches the coast, potentially reaching heights of dozens of meters.
When they reach the coasts, tsunami waves can cause a sudden rise in sea level reaching several meters, submerging entire areas in a matter of minutes. This colossal power leads to massive destruction of homes, infrastructure, and other buildings close to the shoreline. Many structures do not withstand the enormous pressure of the water, even those deemed solid against other disasters. In addition to the immediate shock of the wave, the tsunami generates a fast current capable of carrying away vehicles, debris, and various objects, further intensifying the chaos and damage. These currents also transport a large amount of sediment and mud, engulfing farmland and polluting drinking water supplies. The human consequences are equally tragic, as populations caught off guard often struggle to escape in time.
Intense urbanization near the coast inevitably increases the damage caused by tsunamis. When we build directly on the shoreline, buildings, hotels, and tourist infrastructures become easy targets. The problem also lies in the destruction of natural barriers, such as mangrove forests or coral reefs, which normally act as buffers, weakening the force of giant waves. As a result, without these natural shields, the power of the waves strikes homes head-on. Poorly designed ports and dikes can also worsen the situation, often amplifying the effect of incoming waves instead of stopping them.
Before the arrival of a tsunami, the sea can sometimes suddenly retract, temporarily exposing areas that are normally submerged—this phenomenon is an important precursor sign of an impending tsunami for coastal populations.
The underwater earthquake that generated the tsunami of 2004 in the Indian Ocean released an amount of energy equivalent to several tens of thousands of Hiroshima bombs.
Some animals have demonstrated a surprising ability to sense the impending arrival of a tsunami, fleeing coastal areas to move inland — an observation that is still being studied by scientists today.
In the open ocean, a tsunami wave can travel at the speed of a jet plane, up to about 800 km/h, while remaining almost imperceptible at the surface.
It mainly depends on the location of the earthquake and the distance to the coast. A tsunami can hit the nearest shores in just a few minutes after an earthquake or take several hours to reach more distant areas, sometimes allowing for effective alerts and evacuation measures.
Unlike normal waves caused by the wind, which are limited in energy, tsunami waves result from a massive displacement of water caused by underwater earthquakes, volcanic eruptions, or landslides. They have a much longer wavelength, carry immense amounts of energy, and their height gradually increases as they approach the shore.
Some warning signs include a significant seismic tremor near coastal areas, an unusual and rapid retreat of the sea revealing the ocean floor, or a loud and unusual noise coming from the ocean. If you are in a coastal area and notice these signs, seek to reach an elevated area immediately.
Generally, the average height of tsunamis is around a few meters, but during exceptional events, some waves can exceed several tens of meters. For example, during the 1958 tsunami in Lituya Bay, Alaska, a record wave of 524 meters was observed following a massive landslide.
Yes, although complete prevention is impossible, certain measures can minimize destruction: establishing early warning systems, constructing dikes or breakwater systems, creating vegetated buffer zones, and preparing residents through evacuation plans and regular drills.
Although all coastal areas could potentially be affected, the risk varies significantly depending on plate tectonics and the presence of nearby faults or underwater volcanoes. Regions located near oceanic trenches or in areas of high seismic activity are particularly vulnerable to major tsunamis.
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