(in Japanese means “big wave in the harbor”) – marine gravity waves that arise as a result of shifting up or down the long sections of the seabed in underwater and coastal earthquakes. The speed of propagation is from 50 to 1000 km / h. The altitude in the area of origin is from 0.1 to 5 m, at the coastal – from 10 to 50 m and above.
Tsunamis produce devastating destruction on land. For many centuries, this rampant natural phenomenon keeps people in awe, and therefore there is a lot of nedogovorok about these waves of killers.
Tsunami is a huge wave.
First, it is not one wave, but a whole series of waves coming ashore one after another. Their number ranges from 3 to 25.
Secondly, not every wave is a tsunami. Storm, ship and other waves – this movement is only the upper layer of water, while the tsunami – the movement of its entire thickness.
Tsunami comes from an underwater earthquake.
Moretrejenie becomes the culprit of the tsunami in most cases, but not always. Also, the causes may be typhoons, tropical cyclones, underwater landslides or volcanic eruptions. The largest waves are formed when a cosmic body, a comet or meteorite, enters the ocean. The consequences of such a catastrophe can only be imagined and unlikely to survive. At one time even dinosaurs died from this.
Any sea-frightening threatens the occurrence of a tsunami.
For a tsunami to occur, the displacement of the bottom surface must be lightning fast and large enough to propel the water column. In addition, the focus of the earthquake should not be too deep (up to 20 km.). Therefore, not every change in the relief of the ocean floor generates a giant wave.
Tsunamis occur only in warm seas.
This myth arose from the fact that the most tsunami occurs in the Pacific, where there are sea eruptions and eruptions of underwater volcanoes, and Japan and the Pacific Islands suffer most from their impact. If we talk about landslide tsunami, arising from the collapse of rocks rocks of the sea, then they can happen everywhere! In 1964, due to an earthquake and subsequent collapse of the ice tsunami occurred in Alaska. It amazed with the height of its waves: 60 meters!
Before the tsunami begins, water recedes from the shore.
Canadian mathematician Walter Craig came to the conclusion that in only half of the cases, the water, indeed, departs from the shore, foreshadowing a tsunami. This depends, first of all, on the wavelength, and not on the power of the tsunami, as previously thought.
Tsunami is always a tall wave!
Opening the secret of the occurrence of this natural phenomenon, it must be said that in fact the height of the tsunami depends on its energy. And the farther from the epicenter, the higher the wave level. While in the open sea, the tsunami does not exceed a meter, but it moves at a frenzied speed, on the shallows the wave speed decreases and gains altitude. By the way, the wave generally can not be, and the tsunami will pass, as a series of rapid ebbs and tides. So the tsunami is not just a wall of water falling on the shore, but the movement of the entire water layer, which multiplies its destructive force when encountering land.
Tsunami comes unnoticed, so it is so difficult to escape from it.
Indeed, the distinctive feature of the tsunami is its sudden appearance. But still, it makes itself felt, and if you are careful, you can see the approach of the disaster. If the cause of the giant wave is an earthquake, all on the shore feel the tremors, even if not strong. With a strong movement of water, small marine organisms shine. If a tsunami occurs in cold seas, ice breaks, underwater currents arise. In addition, water can escape from the shore, draining the bottom or, alternatively, slowly pouring.
The first tsunami wave is always the greatest.
This is not true.As tsunami waves move one by one, and the distance between them can reach several tens or even hundreds of kilometers, they reach the coast after a certain time (from a couple of minutes to an entire hour). After the first wave, the shore becomes wet, thereby reducing the resistance for subsequent waves. They are always more destructive.
Animals always feel the approach of a tsunami.
Indeed, during the huge tsunami on the coast of Sri Lanka in 2004, no corpse was found of any animal. Eyewitnesses claim that even the fish tried to hide from the oncoming elements, hiding in corals. But the truth is that not all animals are predictors of a catastrophe. For some, the threat becomes obvious, and the other will not react to it. Therefore, in everything rely on the intuition of our smaller brothers it would be wrong.
Tsunami rescues only a quick flight deep into the coast.
Indeed, this is so, but it is important not just to run away from the shoreline, but also to fulfill the simplest requirements: first, do not move along the riverbed where the tsunami wave will quickly overtake you. Secondly, leaving in the mountains, move up the slope, climbing to a height of at least 30 meters from the coastline. Thirdly, if you are on a ship, boat or any other vessel, it is pointless to seek salvation on the shore, and it is better to go away into the sea. And, finally, we should remember that the tsunami is returning. Only after a certain time you can return to the shore.