Tsunami

Tsunami

Tsunami waves are very high waves of immense destructive power.

Geography

Keywords

tsunami, earthquake, seaquake, sea, wave, high wave, tsunami alert, tectonic plate, epicenter, plate tectonics, disaster, nature, geography

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Scenes

A tsunami is a series of sea waves characterized by a very long wavelength and period. It is generated by the sudden change in sea level, which is caused by underwater earthquakes resulting from the movement of subducting tectonic plates.

The upward jolting movement of a tectonic plate can lift the several kilometer thick layer of water above it, causing a gigantic wave to form and travel for thousands of kilometers, carrying the energy of the earthquake across the ocean until it reaches the coast.

Unlike wind-generated waves, tsunamis affect the body of water in a given section of the ocean, meaning that the entire water column, which can be several kilometers thick, moves out vertically in a given part of the ocean.

While the wavelengths of wind-generated waves range between 100 and 200 m (328.1 and 656.2 ft), that of tsunamis can reach up to 500 km (310.7 mi) in a 5–6 km (3.1–3.7 mi) deep open sea. If the depth of the sea is far less than the wavelength, the speed of the wave is determined by the depth of the water.
Therefore, the tsunami travels at a speed of around 800 km/h (497.1 mph) in the open sea, which is the equivalent of an airliner’s speed. However, wave heights do not exceed 1 m (3 ft), so ships do not even notice them.

The damping of waves is inversely proportional to the wavelength; a tsunami can therefore travel thousands of kilometers with a minimal loss of energy.

Its speed significantly decreases in shallower waters near the coast: it slows down to 80 km/h (49.7 mph) in 50 m (164 ft) deep water. Since its energy is constant, it piles up higher and higher. Eventually, when it hits the coast, the devastating tsunami can be tens of meters high. A number of waves can follow one another with a period of 10–20 minutes.

Often, it is not the crest that reaches the coast first, but the trough; the sea thus recedes dramatically, which is a definite sign of a tsunami. Nevertheless, as it only occurs a few minutes before the crest arrives, it may be too late to evacuate the population.

If a tsunami alert is issued right after an earthquake is detected, there is a 30–60 minute window for evacuation until the arrival of the tsunami, even along the nearest coasts. Moving immediately away from the coast and seeking higher ground are crucial for survival.

Narration

A tsunami is a series of sea waves characterized by a very long wavelength and period. It is generated by the sudden change in sea level, which is caused by underwater earthquakes resulting from the movement of subducting tectonic plates.

The upward jolting movement of a tectonic plate can lift the several kilometer thick layer of water above it, causing a gigantic wave to form and travel for thousands of kilometers, carrying the energy of the earthquake across the ocean until it reaches the coast.

Unlike wind-generated waves, tsunamis affect the body of water in a given section of the ocean, meaning that the entire water column, which can be several kilometers thick, moves out vertically in a given part of the ocean.

While the wavelengths of wind-generated waves range between 100 and 200 m (328.1 and 656.2 ft), that of tsunamis can reach up to 500 km (310.7 mi) in a 5–6 km (3.1–3.7 mi) deep open sea. If the depth of the sea is far less than the wavelength, the speed of the wave is determined by the depth of the water.
Therefore, the tsunami travels at a speed of around 800 km/h (497.1 mph) in the open sea, which is the equivalent of an airliner’s speed. However, wave heights do not exceed 1 m (3 ft), so ships do not even notice them.

The damping of waves is inversely proportional to the wavelength; a tsunami can therefore travel thousands of kilometers with a minimal loss of energy.

Its speed significantly decreases in shallower waters near the coast: it slows down to 80 km/h (49.7 mph) in 50 m (164 ft) deep water. Since its energy is constant, it piles up higher and higher. Eventually, when it hits the coast, the devastating tsunami can be tens of meters high. A number of waves can follow one another with a period of 10–20 minutes.

Often, it is not the crest that reaches the coast first, but the trough; the sea thus recedes dramatically, which is a definite sign of a tsunami. Nevertheless, as it only occurs a few minutes before the crest arrives, it may be too late to evacuate the population.

If a tsunami alert is issued right after an earthquake is detected, there is a 30–60 minute window for evacuation until the arrival of the tsunami, even along the nearest coasts. Moving immediately away from the coast and seeking higher ground are crucial for survival.

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