What is tsunami?
Tsunami, which is also called harbor wave is a massive wave caused by volcanic eruption, landsides and earthquakes occurring under the sea. When the ocean floor is shaken by an earthquake or a volcano erupt under the sea, water are displaced from their position and a tsunami begin to form.
Tsunami can suddenly approach the shore just as water moves back from the shoreline, this forms the trough of the mighty waves that follows behind, because a tsunami is not just one mighty waves, huge waves also follows behind the first one in series.
Tsunami often cause flooding in a massive amount as the wave crashed beyond the shoreline, the force and momentum pushes it by force onto land where it wreak as much havoc as possible. Tsunami also causes deep and large erosion due to the fact that the water washes the foundation of coastal structures away.
Tsunamis are always caused by earthquakes which occurs when seismic waves is caused by the tectonic plates which makes up the earth surface moving against each other.
How tsunami forms ?
A tsunami is caused by underwater slide, a volcanic eruption and at very rare times, a large meteorite strike. Often times, tsunamis are mostly caused by powerful undersea earthquakes. Earthquakes can only cause a major tsunami only if they measure greater than 7.0 on the Richter scale.
Earthquakes that produces tsunami often occur in areas called the subduction zone. In these zones, the earth’s crust pieces presses against one another. Subduction means the siding of on tectonic plate beneath another which later sinks deep into the earth’s mantle.
The friction that occurs between the slow moving two tectonic plates creates a large amount of seismic energy in the earth crust which is later released in the form of earthquake. When a strong earthquake strikes under the sea in a very short distance just below the floor of the sea, it forcefully pushes one of the tectonic plates of the earth crust up which causes the sudden displacement of massive amount of ocean water that spreads out in every direction just from the center of the earthquake, becoming a tsunami.
How often do tsunami occur?
Frequency and pattern of occurrence of tsunami is dependent on the region in the world. Each region has its cycle of generating tsunami with difference in their sizes which ranges from small to large and highly destructive events.
Tsunami occurs with the highest frequency in the pacific ocean and in seas in its margin because the pacific ocean covers a third of the earth’s surface and it is surrounded with chains of mountains, deep trenches of ocean and arcs of island where most earthquakes occur, called the ring of fire.
A tsunami from the north pacific or along the South America’s pacific coast sweeps across the entire pacific about six times in a century.
Tsunami have occurred two times in Chile in the past ten years, once in Haiti, japan, Peru, Solomon and Samoa America and four times in Indonesia,
Areas where tsunami often occur
Tsunami occur most frequently in the Pacific Ocean and in Indonesia because a large number of active submarine earthquake zone are present in the pacific rim at the borders of the ocean. Occurrences of tsunami have also been recorded in the Mediterranean Sea region
Tsunamis have been generated by great earthquakes in the north pacific and along the pacific coast of South America, tsunami was generated in Chile in 1960, in 2000, tsunami occurred in japan.
The Atlantic Ocean and Indian Ocean and smaller bodies of water such as sea of mamara have also had occurrences of tsunami. A local tsunami along the north Anatolian fault zone also happened in 1999 which damaged the bay of izmit.
Deadly tsunamis have occurred over the last ten years in japan, Chile, Indonesia, Haiti, Peru and Samoa- America Samoa.
How big can a tsunami be?
Tsunami waves can be as long as 100 kilometers or 60 miles, and they can even be farther from each other up to an hour apart. These waves have the capacity to cross the entire ocean without great loss in their energy. The Indian waves tsunami was found to travel as far as 3000 miles or 5000 kilometers, carrying alongside a very sufficient force to destroy lives and properties.
When the depth of the ocean is large, tsunamis can travel on the surface at the speed of about 500 miles per hour and cross the entire ocean in less than a day without being noticed, that is why they are said to be as fast as a commercial jet. A tsunami can be less than 30 centimeter in height, less than a foot on the surface of the open ocean and it can propel as high as 30 meters i.e. 100 feet in other places.
When tsunami hits the land, a tsunami’s trough which is the lowest point below the wave’s crest is always the first to reach the shore. It then produce an effect that draws the coastal water to the sea and exposes the sea floors and the harbor. A very important sign of an upcoming tsunami is the retreating of the sea water, the crest of the wave and its massive volume of water then reaches the shore in about five minutes after
Factors that contribute to the severity of tsunami
Some tsunami might not do so much damage while others will wreak a lot of havoc. Factors that determine the severity of a tsunami includes;
A tsunami that hits a densely populated area will cause much more damage than one that will hit a sparsely populated one or the middle of the ocean.
Scientists have an assigned number to represent the amount of seismic energy dissipated by an earthquake. It is measured by the Richter magnitude scale which has been known to be logarithmic, with a step up representing an increase in energy. The more the energy measured in the earthquake, the greater the impact of the tsunami caused.
Weak construction of buildings play a huge role in the destruction made by tsunamis
Activities of human also contributes largely to the environmental ravage caused by tsunami. Building of coastal resort and demolition of natural protection such as mangroves and coral reefs has also increased the severity of tsunami
How is tsunami linked with global warming?
It has been discovered that a rise in sea level as a result of climate change due to global warming poses global hazards and damages from tsunami, even the slightest increase in sea level has been found to increase the risk of tsunamis for worldwide coastal communities. New findings have showed that a rise in sea level shows an increase of flooding farther inland from earthquakes and tsunamis
A rise in sea level can increase the tsunami hazard at a significant rate such that smaller tsunamis can poses the same threat and have the same impact big tsunamis have had in the past due to the increase in the sea level. An increased frequency of inundation always contributed by smaller magnitude if earthquake but poses no threat at normal sea level will cause inundation of a very high level of significance at higher sea level
The high rate of danger caused by tsunami build on already existing difficulties facing coastal communities caused by global warming. There is an increase in the chances of flooding when the tides are high and gradual loss of land near the coasts increases as the earth gets warmer.
How to forecast tsunami
Scientists have always had their hands on deck trying to learn better ways of forecasting how tsunami behaves. However, the current technology we have present only gives us data on tsunami after the damage has already been done.
Scientists are interested particularly in the inundation and run up features that occur after the strike of the waves on the land.
Inundation can be defined as the maximum distance penetrated horizontally inland while run up is the maximum distance the waves reached above the sea level vertically. These parameters are measured by determining the approximate distance of vegetation killed, scattered debris on land and also from eyewitnesses who can account for the incident.
The pacific tsunami warning center continuously monitors seismic event and changing in the tide level, serving the US territories and Hawaiian Islands. They work in conjunction with the west coast and Alaska tsunami warning center, serving the Aleutian island, Oregon, California and Washington states because those regions are prone to submarine earthquakes which have created waves that moved throughout the Pacific Ocean and later strike another place.
Scientists detect tsunamis by coastal tide gauge and open ocean buoys which sends reports to the stations located within the region.
This is done by the tide station measuring changes in the sea level per minutes while the seismograph station takes detailed record of activities of earthquakes. If an earthquake magnitude of 7.5 or more is detected by any center, it causes a tsunami watch to go into effect which sends notification to the civil defense agencies, then the tidal gauge station data are monitored closely so that any sign if a threatening tsunami detected through the set off gauge station, warning issues will be triggered to every areas that can be potentially affected and implementation of evacuation procedures can begin.
The deep ocean assessment and reporting of tsunamis makes use of pressure recorders which they keep at the bottom of the ocean. The recorders are used in detecting little changes in water pressures above it. This system detects tsunami above sea level as small as one centimeter high.
NASA also predicts deadly tsunamis before their occurrence using their NASA jet propulsion laboratory. They use real time data from their global differential GPS network which can predicts the size of a tsunami successfully.
What steps can be taken in future to prevent tsunami
Tsunami is a natural disaster whose occurrence cannot be avoided, scientists have not been able to stop tsunami, but there have been clear instructions put in place to avoid being affected by the troubles of the occurrence.
There are many things you can do to stay safe, in the event of a tsunami, these are divided into things you can do before the occurrence (preparation) and things you should do during the occurrence (safety).
If you live in a tsunami zone, keep emergency food and water supplies, torchlight, first aid kit, and fire extinguishers in quickly accessible locations, and always carry important items and documents in a backpack that can be quickly carried, in case of an emergency occurrence.
For visitors, know if you are in a tsunami zone, get a weather radio to inform you of impending tsunamis or other hazards.
People living in coastal areas or who go there should always be prepared and have their ears on the ground for tsunami news and warnings.
People who have vehicles should keep their vehicle gas tanks at least half full.
You should be informed on local warning systems, regulations and should know and make use of the various weather forecast systems available to them.
You should know available safe and high grounds and how these places can be easily and quickly reached, in case a tsunami occurs suddenly.
You should have a basic knowledge on tsunamis, signs of an impending occurrence such as rapid rise in ocean or sea water, strange noises coming from deep inside the waters, or vibrations near the waters that may be a result of earthquakes.
When you notice strong vibrations near coastal areas, alert the relevant authorities and go to a safe ground, until told otherwise.
A tsunami can be awe-inspiring and fascinating, but very dangerous, do not stay to take pictures, make videos or watch a tsunami occurring, leave immediately, and tell others around to.
Remember the routes to safety, and lead others there too, as there may be visitors and those who are unfamiliar with the area.
In the event of a tsunami hitting a place, do not go there until relevant authorities say it is safe to. A tsunami can hit multiple times.