Tsunami is the movement of water bodies caused by changes in sea level vertical suddenly resulting in very high waves on the shoreline. The word tsunami comes from the Japanese language, which tsu meaning harbor and nami meaning wave. So literally, the tsunami means harbor wave. Tsunamis are often identified by the term seismic sea wave . But experts prefer the use of the word tsunami.
Causes of earthquake – In accordance with its name, the tsunami is often the case in Japan. At least the tsunami has happened about 196 times in Japan. Prior to the development of research as now, likened to a tsunami tidal wave. This is because the appearance of the two events are similar. Tsunami or tidal wave at the same produce waves of water that move inland.
The difference is, the tsunami wave is much larger and longer. Now it is known that a tsunami was not the same as a tidal wave. Causes and morphologically they are different. In addition, the tsunami did not occur around the harbor alone. Can be concluded in fact the word tsunami was less suitable for this natural phenomenon.
Tsunami prone to occur in countries around the Pacific ocean. Because the area around the earth’s shifting plates is more likely to occur. Countries that are prone to benacana Japan, Hawaii, Chilie, India, Bangladesh and Indonesia.
In Indonesia, the tsunami had already happened several times. The most remembered to be a national disaster is certainly happens in Aceh in 2004. It took many years to get up and go fix the damage. Acehnese people call Alon Buluek .
Why of Tsunami
Many factors can cause interference with earth plates that triggered the tsunami. There are at least five things that cause a tsunami. Ie underwater earthquakes, submarine landslides, volcanic eruptions, meteor lacing and human behavior. Here are some of the causes of the tsunami:
1. Earthquake Underwater
The earthquake happened under the sea is the most common cause of tsunamis. Vertical movement in the Earth’s crust(earthquakes) can lead to the seafloor rise or drop suddenly, causing disruption of water balance in it. This resulted in the flow of marine energy, which when up the beach into a tsunami.
However not all earthquakes that occurred under the sea cause a tsunami. Undersea earthquake that caused the tsunami was that meets the following criteria:
- The epicenter was less than 30 kmdibawah sea level
- An earthquake measuring at least 6.5 SR
- Earthquakes with fault pattern up or down
Examples of tsunamis caused by earthquakes is the 2004 Aceh tsunami and tsunami in Japan in 2011 ago.
2. The eruption of Mount Merapi
The volcano spread almost all over the world. The eruption of the volcano that caused the volcanic earthquakes (earthquakes that occurred because of the eruption of Mount Merapi). Although very rare, tsunami caused by the eruption of Mount Merapi is extremely powerful. Especially if merapinya mountains under the sea.
Examples of the tsunami caused by the eruption of the volcano is a major tsunami caused by the eruption of Krakatoa in 1883.
3. Underwater landslide
Submarine landslides caused by the collision between continental plates and oceanic plates caused by the earthquake and peubahan seawater. This process forms the sea suddenly that affect the movement of the volume of water suddenly. At a certain scale caused a tsunami.
The characteristics of tsunamis caused by undersea landslides earthquake magnitude is small but resulted in strong tsunami. Such as might occur in the Coastal Java in 2006.
4. Blow Meteor
Tsunamis can also be caused by a meteor that fell over the sea. Depiction approximately like throwing a bowling ball onto the pool which led to a series of sizable waves at poolside. Additionally, the meteor that crashed into the sea level also causes an imbalance of underwater plates that cause earthquakes. This rarely happens, but the effect is very large tsunami.
5. human tantrum
As beings in the highest strata of classification of organisms, humans also carry greater potential for destruction of the earth. For example in the testing of weapons for war like a nuclear bomb. If testing done at sea, this could potentially cause underwater earthquake with potential for causing a tsunami. Although there has been no incident reported, but experts agree if it is very possible.
In addition to the tsunami as we know, there is also a very large tsunami called megatsunami. Megatsunami is a tsunami that reached a height of over 100 meters. In addition alaska tsunami that reached 520 meters, megatsunami to hit populated areas known to occur around 4.ooo years ago.
Megatsunami can go up to hundreds of meters, with a speed of 890 KM per hour. And DAPT strike the ground as far as 20 kilometers.
Why of megatsunami
Not all causes potentially megatsunami tsunami. Here are three events that trigger megatsunami:
- Landslides are very big which caused the collapse of an island in the sea
- Volcanic eruptions are very large
- The blow huge meteorite
Underwater earthquakes can indeed shift the slabs of the earth, but not strong enough to lead to the collapse of an island that causes megatsunami. Recorded several megatsunami ever happened in human civilization. The most devastating is happening in the gulf Lituya 1958 whose height reaches 524 meters. However, most casualties are megatsunami in Vajont 1963. megatsunami high as 250 meters that claimed some 2,000 lives.
Megatsunami greatest in prehistoric times about 65 million years ago. Megatsunami caused by a meteorite impact that reaches a height of 3 kilometers. This is thought to be the beginning transition to the ice age of the earth.