Causes of a tsunami: signs of occurrence and danger of a tsunami

2024 Author: Henry Conors | [email protected]. Last modified: 2024-02-12 02:47

Over the past decade, the number of natural disasters on the globe has more than doubled. The most dangerous natural phenomena include tsunamis - huge deadly waves.

Do you think you know enough about this? Then try answering these simple questions:

name the causes of the tsunami;
list the signs by which you can determine its approach;
tell me what to do to avoid being hit by the killer wave.

Didn't work? Then read this article carefully, perhaps this information will someday help save your life.

What is a tsunami?

It will be about the tsunami - the causes and consequences of this phenomenon should be known to modern society. The well-known term came to us from Japan, and it is not surprising because it is this country that most often suffers from killer waves. Tsunami in Japanese is denoted by two characters: 津 - "bay, port, bay" and 波 - "wave". Therefore, in direct translation, thisthe word means "wave in the bay". These are huge waves that originate in the depths of the ocean and crash on the shore with great destructive force.

The damaging factors of a tsunami can be defined as primary and secondary. Primary include:

wave hit;
air wave preceding flooding;
hydrodynamic pressure;
secondary are:
complete flooding of the area;
stranding ships;
destruction of buildings, roads, bridges, power lines and other objects in the path of the wave;
death of all life;
soil erosion, destruction of agricultural plantations;
fires.

Where is this phenomenon most common?

The causes of tsunamis are most often associated with geological activity. With the greatest probability, a similar phenomenon can be found on the Pacific coast. This is primarily due to the high geoactivity of this basin. Over the past millennium, these territories have been hit by killer waves more than 1000 times. At the same time, this phenomenon was observed several times less frequently in the Indian and Atlantic Oceans.

On the territory of Russia, the most dangerous, in terms of tsunamis, are the coasts of the Kuriles and Kamchatka, as well as Sakhalin Island.

Killer Wave Parameters

Considering the causes of a tsunami, it is worth first of all to talk about what parameters such waves are characterized by, how they can bemeasure. Like any other wave, a tsunami has a length, height and speed.

Wavelength is the horizontal distance between two peaks (crests) of adjacent waves. The average killer wavelength can range from 150 to 300 km.
Height is the distance between the crest and the bottom of one wave. Above the center of the tsunami, this figure can be quite small - from 1 to 5 meters.
Speed is the linear speed of movement of a certain element, for example, a comb. Most often, this figure ranges from 500 to 1000 km / h, which, you see, is a lot.

All indicators of a tsunami wave depend on the depth of the place of origin. The deeper the wave originated, the longer its length will be and the higher the propagation speed, but the height will be just small. For example, the propagation speed of a tsunami in the Pacific Ocean, whose average depth is about 4 km, is approximately 700–800 km/h. When approaching the coastline, the wave propagation speed sharply decreases to 80–100 km/h. Thus, the shallower the depth, the shorter the waves, but the height increases sharply when approaching the coast. In some cases, it can reach 45–50 meters.

Intensity

Before we talk about what causes a tsunami, let's look at the parameters of the intensity of this phenomenon. Yes, yes, a tsunami, like an earthquake, has a division expressed in points. There are six levels in total and they meannext:

1 point - the phenomenon is very weakly expressed, such a tsunami can only be registered with special instruments - seaographers;
2 points - a rather weak wave that can only flood a flat coast; mostly experts can also notice it;
3 points - medium power tsunami, anyone can notice it; it is characterized by flooding of the flat coast, light destruction of coastal buildings; light boats may also be washed ashore;
4 points - a fairly severe natural disaster; the coast is completely flooded, and all coastal buildings have significant damage; light motorized vessels and rather large sailboats were washed ashore and then washed back; the coastline is littered with sand, silt and tree debris; human casu alties are also likely;
5 points - a very strong phenomenon, accompanied by numerous victims; the coastline is severely destroyed for many hundreds of meters, large ships are thrown ashore; nearby rivers burst their banks from severe storm surge;
6 points - catastrophic consequences; the land is completely flooded for many kilometers inland, there are massive human casu alties, there is complete devastation of the surrounding territories.

What causes killer waves?

So we come to the question of why these terrible waves arise. To begin with, let's briefly list the causes of the tsunami:

landslides;
earthquakes;
volcanic eruptions;
fallingmeteorites;
human activity.

causes of tsunamis and their possible consequences

The main cause of a killer wave is an underwater earthquake with a sharp rise or fall in the level of the seabed. About 85% of all tsunamis occur for this reason. But not every underwater earthquake is accompanied by the appearance of a huge wave. Most often this happens when the focus is not too deep.

Landslides are another reason. They account for about 7-8% of the rampant elements. This cause of storm waves and tsunamis seems to be secondary, since landslides most often occur as a result of earthquakes.

The third reason is underwater volcanic eruptions. Strong underwater eruptions have about the same effect as earthquakes. The largest and most famous eruption happened in 1883. The volcano Krakatau caused a huge tsunami that destroyed more than 5,000 ships, killing about 36,000 people around the world.

The rapidly developing nuclear energy has formed the prerequisites for the emergence of another reason for the appearance of giant waves - human activity. Various deep-sea tests, such as atomic explosions, are also capable of causing a phenomenon such as a tsunami.

A very small, but still percentage, is given to cosmic phenomena, for example, the fall of meteorites.

It is worth noting that giant waves are most often the result of not one, but a number of factors. And in this case they are especially destructive. Herethese may be the main causes of tsunamis.

Consequences

One of the most terrible consequences of the tsunami, of course, is human casu alties. Even one life of a person buried by a wave is already a huge grief. What can we say about hundreds and thousands of dead.

In addition, tsunamis cause salinization and erosion of large sections of the coast, as well as complete flooding of coastal areas. All ships moored near the shore are destroyed, and nearby buildings and structures can be destroyed to the ground.

How to recognize an approaching tsunami?

The causes of the tsunami are more or less clear, but how to recognize signs that portend trouble?

The very first approaching natural disasters are usually felt by birds and animals that begin to leave their homes. The mass “moving” of animals can begin both a few hours and a few days before the disaster. Probably, birds and animals feel some energy waves sent by mother earth. In fact, animals are affected by an electromagnetic field: a whole stream of charged ions rises from the surface of the earth into the atmosphere, charging the air with electricity to the limit. By the way, not only animals feel this phenomenon - many so-called weather-dependent people begin to have unbearable headaches.

If you live on the coast, get yourself an aquarium and carefully observe its inhabitants. That's how they do itthe Japanese, who for many decades have been determining the approach of seismic activity by the behavior of aquarium catfish. In anticipation of shocks, these fish behave very restlessly, trying to literally jump out of the aquarium.

Clear signs of an approaching tsunami may look like this:

water quickly and suddenly leaves the shore, leaving a wide strip of sand;
there are signs of a small (or strong) earthquake, although this item is not at all necessary, since the epicenter of the earthquake may be far in the ocean, and not be felt at all on the coast;
moving waves accompanied by sounds like thunder;
changing the behavior of animals, birds and fish (they can wash ashore).

What should you do if you notice a wave is coming?

If you notice such causes of a tsunami as an earthquake or a meteorite fall, or see clear signs of its approach, do not hesitate a second. Take your most valuable things and documents with you, take your children and elderly relatives, and leave the coast deep into the mainland as soon as possible. Arrange a meeting point with your family in advance in case you lose each other.

If there is no way to quickly leave a dangerous place, look for other ways to escape. It can be some kind of natural hill - a mountain or a hillock. High capital buildings made of stone or concrete are also suitable. It is best if they are still at least a little further from the coast.

You need to move the shortest way,avoiding the banks of rivers and various water bodies - bridges, dams, reservoirs. A distance of at least 3–5 km from the coastline can be considered safe.

Try to stay calm - panic only gets in the way. The occurrence of a tsunami is usually fixed by instruments and the warning system is turned on. Never ignore these sounds, even if it turns out to be a false alarm several times.

Never stay to watch a tsunami or approach the shore for 3-4 hours after the first wave arrives. The fact is that the wave is rarely one - the second, and even the third can come in 30 minutes or even in 3 hours. Make sure it's over before returning.

Knowing these simple rules can truly save your life. Follow them whenever you notice the first signs of a killer wave coming. Do not ignore the siren, even if everyone around you says that the alarm is false.

Conclusion

Now you know exactly the causes of tsunamis and their possible consequences. I would like this knowledge to really help in a difficult situation. Remember, a tsunami is a very fast and extremely dangerous natural disaster. Knowing the causes of this phenomenon and the elementary rules of behavior can really save your life.