What is a tsunami, how it differs from a tidal wave and what have been the most devastating tsunamis in history. Discover the tsunami risk.
Tsunami
Tsunamis are among the most destructive natural phenomena on Earth . They are gigantic waves that can travel at incredible speeds and devastate entire coastal cities in a matter of minutes. Tsunamis and tidal waves are often confused , but in reality they are not exactly the same thing. In this article we will discover the meaning of the term tsunami, the difference with a tidal wave and some of the greatest events in history linked to this phenomenon.
What is a tsunami?
The term tsunami comes from Japanese (津波) and literally means ” harbor wave “. It is a series of anomalous waves that are generated due to a sudden and violent disturbance of the seabed. This phenomenon can be triggered by various natural causes, including:
- Underwater earthquakes (the most common cause)
- Volcanic eruptions
- Submarine or coastal landslides
- Impact of meteorites or asteroids in the ocean
Unlike normal waves , which are generated by the wind and only affect the surface of the sea, a tsunami involves the entire water column , from the surface to the bottom. This allows the waves to travel at impressive speeds, up to 800 km/h in the open sea. As a tsunami approaches the coast, the speed decreases , but the height of the wave increases dramatically, creating a wall of water that can overwhelm everything in its path.
Difference between tsunami and tidal wave
Many people use the terms tsunami and tidal wave as synonyms, but in reality there is a difference between the two phenomena:
- A tsunami is an underwater earthquake, that is, a movement of the earth’s crust that occurs under the sea or near the coast. If the tsunami is very strong and displaces a large amount of water, it can generate a tsunami .
- A tsunami , on the other hand, is the result of a tsunami (or other causes), that is, a giant wave that propagates through the ocean.
Therefore, while every tsunami can be caused by a tsunami, not all tsunamis generate tsunamis. For example, if an earthquake occurs at sea but does not cause a significant vertical movement of the seabed, no anomalous waves will form.
What was the highest tsunami in the world?
The highest tsunami ever recorded occurred on July 9, 1958, in Lituya Bay, Alaska. A massive earthquake of magnitude 7.8 caused a giant landslide, which sent a huge amount of rock and ice crashing into the water . The impact created a colossal wave that reached a record height of 524 meters!
For comparison, the tsunami at Lituya Bay was taller than the Empire State Building in New York . Fortunately, since it was a sparsely populated area, there were few casualties, but the power of the wave swept away entire forests and changed the landscape forever.
How high was the 2004 tsunami?
One of the most devastating tsunamis in recent history occurred on December 26, 2004 , known as the Indian Ocean tsunami . This tsunami was caused by a magnitude 9.1 undersea earthquake that occurred off the coast of Sumatra , Indonesia .
The waves reached 30 metres high in some areas and hit with devastating force the coasts of Indonesia , Thailand , Sri Lanka , India , the Maldives and even Somalia , thousands of kilometres away.
The toll was tragic: over 230,000 victims in 14 countries . This tsunami is considered one of the worst natural disasters in history.
What was the last tsunami in Italy?
In Italy, tsunamis are very rare compared to the Pacific or Indian Ocean areas, but there have been several episodes in history. The last significant tsunami occurred on October 30, 2016 , following the 6.5 magnitude earthquake that struck central Italy .
Although it did not cause giant waves like those in the Pacific Ocean, the earthquake generated small tsunamis in the Adriatic Sea, with variations in sea level observed along the coasts of Marche and Abruzzo . Fortunately, there were no damages or casualties.
One of the most serious Italian tsunamis dates back to 28 December 1908 , when a strong earthquake of magnitude 7.1 in the Strait of Messina generated a rogue wave that devastated the coasts of Messina and Reggio Calabria, causing over 100,000 deaths .
What are the tsunami risk areas in Italy?
Italy is not among the countries most exposed to tsunamis, but some areas present a medium-high risk, in particular:
- The Strait of Messina (where the 1908 tsunami occurred)
- The eastern coast of Sicily (Catania and Syracuse, due to the risk linked to Etna)
- The Gulf of Naples (due to Vesuvius and the Phlegraean Fields)
- Sardinia and the Tyrrhenian Sea ( for possible earthquakes in the western Mediterranean)
The National Institute of Geophysics and Volcanology (INGV) constantly monitors the tsunami risk in Italy and has activated an early warning system to prevent disasters.
How to protect yourself from a tsunami?
Although the risk is lower in Italy, it is always useful to know the safety measures in case of a tsunami:
- If you are in a coastal area and feel a strong earthquake , move away from the beach immediately.
- Pay attention to natural signs: a sudden retreat of the sea can be a sign of an approaching tsunami.
- Follow the authorities’ directions and reach the higher areas .
- If you are at sea , move away from the coast and head towards deeper water .
Conclusion
Tsunamis are impressive phenomena that can cause enormous devastation , but knowing more about them helps prevent their effects. Although the risk in Italy is lower than in other parts of the world, some areas could be subject to anomalous waves in the event of strong underwater earthquakes. For this reason, it is important to inform yourself and follow the safety rules.
