Here is a compilation of essays on ‘Tsunami’ for class 6, 7, 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Tsunami’ especially written for school and college students.
Essay on Tsunami
- Essay on the Definition of Tsunami
- Essay on the Meaning of Tsunami
- Essay on the Characteristics of Tsunami
- Essay on the Prediction of Tsunami
- Essay on the Causes of Tsunami
- Essay on the Generation of Tsunamis
- Essay on the Risk Assessment of Tsunami
- Essay on the Capacity-Building for Tsunami
- Essay on Preparedness for Tsunamis
Essay # 1. Definition of Tsunami:
The word tsunami is a Japanese word, represented by two characters: tsu, meaning, ‘harbour’, and nami meaning, ‘wave’. Tsunami is a set of ocean waves caused by any large, abrupt disturbance on the sea- surface. If the disturbance is close to the coastline, local tsunamis can demolish coastal communities within minutes. A very large disturbance can cause local devastation and export tsunami destruction thousands of miles away.
Tsunamis rank high on the scale of natural disasters. Since 1850 alone, tsunamis have been responsible for the loss of over 420,000 lives and billions of dollars of damage to coastal structures and habitats. Most of these casualties were caused by local tsunamis that occur about once per year somewhere in the world.
For example, the December 26, 2004, tsunami killed about 130,000 people close to the earthquake and about 58,000 people on distant shores. Predicting when and where the next tsunami will strike is currently impossible. Once the tsunami is generated, forecasting tsunami arrival and impact is possible through modelling and measurement technologies.
Essay # 2. Meaning of Tsunami:
The phenomenon we call tsunami is a series of large waves of extremely long wavelength and period usually generated by a violent, impulsive undersea disturbance or activity near the coast or in the ocean. When a sudden displacement of a large volume of water occurs, or if the sea floor is suddenly raised or dropped by an earthquake, big tsunami waves can be formed by forces of gravity.
The waves travel out of the area of origin and can be extremely dangerous and damaging when they reach the shore. The word tsunami (pronounced tsoo-nah’-mee) is composed of the Japanese words ‘tsu’ (which means harbour) and ‘nami’ (which means ‘wave’).
Often the term, ‘seismic or tidal sea wave’ is used to describe the same phenomenon, however the terms are misleading, because tsunami waves can be generated by other non-seismic disturbances such as volcanic eruptions or underwater landslides, and have physical characteristics different from tidal waves.
The tsunami waves are completely unrelated to the astronomical tides—which are caused by the extra-terrestrial, gravitational influences of the moon, sun, and the planets. Thus, the Japanese word ‘tsunami’, meaning ‘harbour wave’ is correct, official and ail-inclusive term. It has been internationally adopted because it covers all forms of impulsive wave generation.
Essay # 3. Characteristics of Tsunami:
Tsunami in the deep ocean may have very long wave length of hundreds of kilometre and travels at about 800 km per hour, but an amplitude of only about 1 km. It remains undetected by ships in the deep sea. However, when it approaches the coast its wavelength diminishes but amplitude grows enormously, and it takes very little time to reach its full height.
Computer model can provide tsunami arrival, usually within minutes of the arrival time. Tsunamis have great erosion potential, stripping beaches of sand, coastal vegetation and dissipating its energy through the destruction of houses and coastal structures.
In the open ocean, tsunamis would not be felt by ships because the wavelength would be hundreds of miles long, with an amplitude of only a few feet. This would also make them unnoticeable from the air. As the waves approach the coast, their speed decreases and their amplitude increases. Unusual wave heights have been known to be over 100 feet high. However, waves that are 10 to 20 feet high can be very destructive and may cause many deaths or injuries.
From an initial tsunami generating source area, waves travel outward in all the directions much like the ripples caused by throwing a rock into a pond. As these waves approach coastal areas, the time between successive wave crests varies from 5 to 90 minutes. The first wave is usually not the largest in the series of waves, nor it is the most significant.
Furthermore, one coastal community may experience no damaging waves while the other, located not that far away, may experience destructive deadly waves. Depending on a number of factors, some low-lying areas could experience severe inland inundation of water and debris of more than 1,000 feet.
Essay # 4. Prediction of Tsunamis:
There is no historic record of a tsunami in the Indian Ocean: the only earlier reference to a tsunami was in relation to the 1941 Andaman Island earthquake and prior to that in 1880s. That too is not documented. Tsunami is most infrequent and it is almost impossible to predict as compared to a normal earthquake.
Since this phenomenon has been experienced mostly in the pacific ocean region stretching from Chile in Latin America to Japan in far East-Asia. The international group for the Tsunami warning system does not extend to Indian Ocean.
The area of Sumatra where the earthquake occurred, was considered to lie in an endangered zone by many geologists and other experts, even though the exact date and time of catastrophe could not be forecast. The strength of the quake could not have been predicted nor its location below the ocean. No one had thought that such a dangerous tsunami would result as it happened in December, 2004.
Early warning can be made about the presence and advance of a tsunami. But this can be practical only for those who are some distance away from ground zero. These waves could be detected by specially designed synchronous satellites mandated to keep a watch. A more reliable method might be to locate several pressure sensors at the bottom of the ocean.
These sensors would detect the periodic changes in pressure produced by the variations of the water column height above caused by the passing waves. They would send the information up to the floating buoys using ultrasound chirp signal.
The buoys could be equipped to communicate through satellite communication with control, analysis and operational centres, which could then issue appropriate warnings to the people in potential impact zones. Although prediction of Tsunamis is an uphill task, however, disaster mitigation centres can be established in those areas, where there is an urgent need to provide relief and rehabilitation facilities.
The global tsunami warning system set up in 1965 is said to predict where tsunamis will strike up to 14 hours in advance, using network of seismic centres and tidal gauges attached to buoys in the oceans. According to the scientists in the Aeronautics and Space Administration (NASA), a reliable early detection system for tsunamis is yet to be developed.
Essay # 5. Causes of Tsunami:
A tsunami is a large ocean wave that is caused by sudden motion on the ocean floor. This sudden motion could be an earthquake, a powerful volcanic eruption, or an underwater landslide. The impact of a large meteorite can also cause a tsunami. Tsunamis travel across the open ocean at great speeds and convert into large deadly waves in the shallow water of a shoreline.
(i) Subduction Zones are Potential Tsunami Locations:
Most tsunamis are caused by earthquakes generated in a subduction zone, an area where an oceanic plate is being forced down into the mantle by tectonic plate forces. The friction between the subducting plate and the overriding plate is enormous. This friction prevents a slow and steady rate of subduction and instead the two plates become ‘stuck’.
(ii) Accumulated Seismic Energy:
As the stuck plate continues to descend into the mantle the motion causes a slow distortion of the overriding plate. The result is an accumulation of energy very similar to the energy stored in a compressed spring. Energy can accumulate in the overriding plate over a long period of time—decades or even centuries.
(iii) Earthquake Causes Tsunami:
Energy accumulates in the overriding plate until it exceeds the frictional forces between the two stuck plates. When this happens, the overriding plate snaps back into an unrestrained position. This sudden motion is the cause of the tsunami—because it gives an enormous shove to the overlying water. At the same time, inland areas of the overriding plate are suddenly lowered.
(iv) Tsunami Races away from the Epicentre:
The moving wave begins travelling out from where the earthquake has occurred. Some of the water travels out across the ocean basin, and, at the same time, water rushes towards the land to flood the recently lowered shoreline.
Essay # 6. Generation of Tsunamis:
Tsunamis are commonly generated by earthquakes in marine and coastal regions. Major tsunamis are produced by large (greater than 7 on the Richter scale), shallow focus (< 30 km depth in the earth) earthquakes associated with the movement of oceanic and continental plates. They frequently occur in the Pacific, where dense oceanic plates slide under the lighter continental plates.
Propagation of Waves:
Because earth movements associated with large earthquakes are thousands of square kilometres in area, any vertical movement of the seafloor immediately changes the sea-surface. The resulting tsunami propagates as a set of waves whose energy is concentrated at wavelengths corresponding to the earth movements (-100 km), wave heights determined by vertical displacement (~lm) and wave directions determined by the adjacent coastline geometry.
Because each earthquake is unique, every tsunami has unique wavelengths, wave heights and directionality. From a tsunami-warning perspective, this makes the problem of forecasting tsunamis in real time daunting.
How do Earthquakes Generate Tsunamis?
By far, the most destructive tsunamis are generated from large, shallow earthquakes with an epicentre or fault line near or on the ocean floor. These usually occur in regions of the earth characterized by tectonic subduction along tectonic plate boundaries. The high seismicity of such regions is caused by the collision of tectonic plates.
When these plates move past each other, they cause large earthquakes, which tilt, offset, or displace large areas of the ocean floor from a few kilometres to as much as a 1,000 km or more. The sudden vertical displacements over such large areas disturb the ocean’s surface, displace water, and generate destructive tsunami waves. The waves can travel great distances from the source region, spreading destruction along their path.
For example, the Great 1960 Chilean tsunami was generated by a magnitude 8.3 earthquake that had a rupture zone of over 1,000 km. Its waves were destructive not only in Chile, but also as far away as Hawaii, Japan and elsewhere in the Pacific. It should be noted that not all earthquakes generate tsunamis. Usually, it takes an earthquake with a Richter magnitude exceeding 7.5 to produce a destructive tsunami.
How do Volcanic Eruptions Generate Tsunamis?
Although relatively infrequent, violent volcanic eruptions represent impulsive disturbances, which can displace a great volume of water and generate extremely destructive tsunami waves in the immediate source area. According to this mechanism, waves may be generated by the sudden displacement of water caused by a volcanic explosion, by a volcano’s slope failure, or more likely by a phreatomagmatic explosion and collapse/engulfment of the volcanic magmatic chambers.
One of the largest and most destructive tsunamis ever recorded was generated on August 26, 1883 after the explosion and collapse of the volcano of Krakatoa (Krakatau), in Indonesia. This explosion generated waves that reached 135 feet, destroyed coastal towns and villages along the Sunda Strait in both the islands of Java and Sumatra, killing 36,417 people. It is also believed that the destruction of the Minoan civilization in Greece was caused in 1490 B.C. by the explosion/collapse of the volcano of Santorin in the Aegean Sea.
How do submarine landslides, rock falls and underwater slumps generate tsunamis?
Less frequently, tsunami waves can be generated from displacement of water resulting from rock falls, icefalls and sudden submarine landslides or slumps. Such events may be caused impulsively from the instability and sudden failure of submarine slopes, which are sometimes triggered by the ground motions of a strong earthquake.
For example, in 1980’s, the earth moving and construction work of an airport runway along the coast of Southern France, triggered an underwater landslide, which generated destructive tsunami waves in the harbour of Thebes.
Major earthquakes are suspected to cause many underwater landslides, which may contribute significantly to tsunami generation. For example, many scientists believe that the 1998 tsunami, which killed thousands of people and destroyed coastal villages along the northern coast of Papua-New Guinea, was generated by a large underwater slump of sediments, triggered by an earthquake.
In general, the energy of tsunami waves generated from landslides or rock falls is rapidly dissipated as they travel away from the source and across the ocean, or within an enclosed or semi-enclosed body of water—such as a lake or a fjord. However, it should be noted that the largest tsunami wave ever observed anywhere in the world was caused by a rock fall in Lituya Bay, Alaska on July 9, 1958.
Triggered by an earthquake along the Fairweather fault, an approximately 40 million cubic metre rock fall at the head of the bay generated a wave, which reached the incredible height of 520 metre wave (1,720 feet) on the opposite side of the inlet.
An initial huge solitary wave of about 180 metres (600 feet) raced at about 160 kilometres per hour (100 mph) within the bay debarking trees along its path. However, the tsunami’s energy and height diminished rapidly away from the source area and, once in the open ocean, it was hardly recorded by tide gauge stations.
Can Asteroids, Meteorites or Man-Made Explosions Cause Tsunamis?
Fortunately, for mankind, it is indeed very rare for a meteorite or an asteroid to reach the earth. No asteroid has fallen on the earth within recorded history. Most meteorites burn as they reach the earth’s atmosphere. However, large meteorites have hit the earth’s surface in the distant past. This is indicated by large craters, which have been found in different parts of the earth.
Also, it is possible that an asteroid may have fallen on the earth in prehistoric times—the last one some 65 million years ago during the Cretaceous period. Since, the evidence of the fall of meteorites and asteroids on earth exists, we must conclude that they have also fallen in the oceans and seas of the earth, particularly since four-fifths of our planet is covered by water.
The fall of meteorites or asteroids in the earth’s oceans has the potential of generating tsunamis of cataclysmic proportions. Scientists studying this possibility have concluded that the impact of moderately large asteroid, 5-6 km in diameter, in the middle of the large ocean basin such as the Atlantic Ocean, would produce a tsunami that would travel all the way to the Appalachian Mountains in the upper two-thirds of the United States. On both sides of the Atlantic, coastal cities would be washed out by such a tsunami.
An asteroid 5-6 kilometres in diameter impacting between the Hawaiian Islands and the West Coast of North America, would produce a tsunami which would wash out the coastal cities on the West coasts of Canada, U.S. and Mexico would cover most of the inhabited coastal areas of the Hawaiian islands.
Conceivably, tsunami waves can also be generated from very large nuclear explosions. However, no tsunami of any significance has ever resulted from the testing of nuclear weapons in the past. Furthermore, such testing is presently prohibited by international treaty.
Since 1946, the tsunami warning system has provided warnings of potential tsunami danger in the Pacific basin by monitoring earthquake activity and the passage of tsunami waves at tide gauges. However, neither seismometers nor coastal tide gauges provide data that allow accurate prediction of the impact of a tsunami at a particular coastal location.
Monitoring earthquakes gives a good estimate of the potential for tsunami generation, based on earthquake size and location, but gives no direct information about the tsunami itself. Tide gauges in harbors provide direct measurements of the tsunami, but the tsunami is significantly altered by local bathymetry and harbour shapes, which severely limits their use in forecasting tsunami impact at other locations.
Partly because of these data limitations, 15 of 20 tsunami warnings issued since 1946 were considered false alarms because the tsunami that arrived was too weak to cause damage.
Essay # 7. Risk Assessment of Tsunami:
A preliminary risk assessment has been done for the Indian coast w.r.t. tsunamis taking into account the seismo-tectonic setting, historical seismicity and past-tsunami events.
The east and west coasts of India and the island regions are likely to be affected by Tsunamis generated mainly by subduction zone related earthquakes from the two potential source regions, viz., the Andaman- Nicobar-Sumatra Island Arc and the Makran subduction zone north of Arabian Seat.
Depending upon the location of the earthquake, the response time for evacuation of coastal population could range between 10 minutes to few hours. Tsunami modelling studies indicate that the least response time available is for the Andaman & Nicobar Islands which are situated right on the subduction zone capable of triggering tsunami earthquakes.
Considering that a credibly worst earthquake of 7.5 or higher occurs near Nicobar, the travel time to the nearest coast in Nicobar would be approximately 20-30 minutes and for the Indian mainland about 2-3 hours.
Where and How Frequently are Tsunamis Generated?
Tsunamis are disasters that can be generated in all of the world’s oceans, inland seas, and in any large body of water. Each region of the world appears to have its own cycle of frequency and pattern in generating tsunamis that range in size from small to the large and highly destructive events. Most tsunamis occur in the Pacific Ocean and its marginal seas.
The reason is that the Pacific covers more than one-third of the earth’s surface and is surrounded by a series of mountain chains, deep-ocean trenches and island arcs called the ‘ring of fire’—where most earthquakes occur (off the coasts of Kamchatka, Japan, the Kuril Islands, Alaska and South America). Many tsunamis have also been generated in the seas which border the Pacific Ocean.
Tsunamis are generated by shallow earthquakes all around the Pacific, but those from earthquakes in the tropical Pacific tend to be modest in size. While such tsunamis in these areas may be devastating locally, their energy decays rapidly with distance. Usually, they are not destructive a few hundred kilometres away from their sources.
That is not the case with tsunamis generated by great earthquakes in the North Pacific or along the Pacific coast of South America. On an average of about half-a-dozen times per century, a tsunami from one of these regions sweeps across the entire Pacific, is reflected from distant shores, and sets the entire ocean in motion for days.
For example, the 1960 Chilean tsunami caused death and destruction throughout the Pacific. Hawaii, Samoa, and Easter Island all recorded runups exceeding 4 m; 61 people were killed in Hawaii. In Japan 200 people died.
A similar tsunami in 1868 from northern Chile caused extensive damage in the Austral Islands, Hawaii, Samoa and New Zealand. Although not as frequent, destructive tsunamis have also been generated in the Atlantic and the Indian Oceans, the Mediterranean Sea and even within smaller bodies of water, like the Sea of Marmara, in Turkey.
In 1999, a large earthquake along the North Anatolian Fault zone, generated a local tsunami, which was particularly damaging in the Bay of Izmit. In the last decade alone, destructive tsunamis have occurred in Nicaragua (1992), Indonesia (1992, 1994, 1996), Japan (1993), Philippines (1994), Mexico (1995), Peru (1996, 2001), Papua-New Guinea (1998), Turkey (1999), Vanuatu (1999) and India-Sri Lanka (2004).
How does Tsunami Energy Travel across the Ocean and How far can Tsunami Waves Reach?
Once a tsunami has been generated, its energy is distributed throughout the water column, regardless of the ocean’s depth. A tsunami is made up of a series of very long waves. The waves will travel outward on the surface of the ocean in all directions away from the source area, much like the ripples caused by throwing a rock into a pond.
The wavelength of the tsunami waves and their period will depend on the generating mechanism and the dimensions of the source event. If the tsunami is generated from a large earthquake over a large area, its initial wavelength and period will be greater. If the tsunami is caused by a local landslide, both its initial wavelength and period will be shorter. The period of the tsunami waves may range from 5 to 90 minutes.
The wave crests of a tsunami can be a thousand km long, and from a few to a hundred kilometre or more apart as they travel across the ocean. On the open ocean, the wavelength of a tsunami may be as much as two hundred kilometres, many times greater than the ocean depth, which is in the order of a few kilometres. In the deep ocean, the height of the tsunami from trough to crest may be only a few centimetres to a metre or more—again depending on the generating source.
Tsunami waves in the deep ocean can travel at high speeds for a long period of time for thousands of kilometres and lose very little energy in the process. The deeper the water, the greater the speed of tsunami waves will be. For example, at the deepest ocean depths the tsunami wave speed will be as much as 800 km/hr, about the same as that of a jet aircraft.
Since the average depth of the Pacific Ocean is 4000 m (14,000 feet), wave speed of tsunami will average about 200 m/s or over 700 km/hr (500 mph). At such high speeds, a tsunami generated in Aleutian Islands may reach Hawaii in less than four and a half hours. In 1960, great tsunami waves generated in Chile reached Japan, more than 16,800 km away in less than 24 hours, killing hundreds of people.
Essay # 8. Capacity-Building for Tsunami:
UNDP describes ‘capacity-building’ as the creation of an enabling environment with appropriate policy and legal frameworks, institutional development, including community participation (of women in particular), human resource development and strengthening of managerial systems. It adds that capacity-building is a long-term, continuing process, in which all stakeholders participate (ministries, local authorities, non-governmental organizations, and water user associations, professional associations, academics and others).
Capacity may include physical, institutional, social or economic means as well as skilled personal or collective attributes such as leadership and management. Capacity may also be described as capability.
Capacity-building is much more than training and includes the following:
i. Human resource development, the process of equipping individuals with the understanding, skills and access to information, knowledge and training that enables them to perform effectively,
ii. Organizational development, the elaboration of management structures, processes and procedures, not only within organizations but also the management of relationships between the different organizations and sectors (public, private and community).
iii. Institutional and legal framework development, making legal and regulatory changes to enable organizations, institutions and agencies at all levels and in all sectors to enhance their capacities.
Approach to Capacity-Building:
The National Policy on Disaster Management (NPDM) describes its approach to capacity development. A strategic approach to capacity development can be addressed effectively only with the active and enthusiastic participation of the stakeholders.
This process comprises of awareness generation, education, training, research and development (R&D) etc. It further addresses to put in place an appropriate institutional framework, management systems and allocation of resources for efficient prevention and handling of disasters.
The approach to capacity development includes:
i. Accordingly, priority to training for developing community based DM, systems for their specific needs in view of the regional diversities and multi-hazard vulnerabilities,
ii. Conceptualization of community based DM systems at the national level through a consultative process involving the States and other stakeholders with the state and local level authorities in-charge of implementation,
iii. Identification of knowledge-based institutions with proven performance,
iv. Promotion of international and regional cooperation.
Essay # 9. Preparedness for Tsunamis — What To Do?
The United Nations has been engaged for fifteen years in a process of creating awareness and promoting the development of policies to diminish the loss of life and property from natural and man- made disasters. This was first done through efforts during the International Decade for Natural Disaster Reduction and then through the International Strategy for Disaster Reduction that followed, as well as by the establishment of the UN Disaster Task Force, in which UNESCO and IOC participate.
Awareness-raising and policy-development issues in disaster reduction were raised to a higher level at the World Conference on Disaster Reduction held in Kobe, Japan, in January 2005 in which more than 6,000 delegates from 155 countries, and numerous inter-governmental and non-governmental agencies, United Nations, and other specialized organizations participated.
Early Warning Systems can save lives. In particular, a number of elements are critical for an effective system to operate, and can be summarized as follows:
i. Proper instruments that enable the early detection of potentially harmful earthquakes and tsunamis. The data obtained by these instruments must be readily available to all nations continuously and in real-time to be effective.
ii. Warning systems that reliably inform the vulnerable populations immediately and in an understandable and culturally appropriate way. The Warning Centre must be able to analyze and forecast the impact of tsunamis on coasts in advance of the waves’ arrival and the local, regional, and/or national Disaster Management Organizations (DMOs) must be able to immediately disseminate information of the threat to enable evacuation of all vulnerable communities. The communication methods must be reliable, robust and redundant, and work closely with the mass media and telecommunication providers to accomplish this broadcast.
iii. Awareness activities that enable ordinary citizens to recognize a tsunami so that they know what to do. Citizens should recognize tsunami’s natural warning signs and respond immediately. This is especially true for the case of a local tsunami, which may hit within minutes and before an official tsunami warning can reach their communities.
iv. Preparedness activities which educate and inform a wide populace, including government responders and those providing lifeline and critical infrastructure services, on the procedures and activities that must be taken to ensure public safety. Drills and exercises before an actual event, and proactive outreach and awareness activities are essential for reducing tsunami impact.
v. Planning activities which identify and create the public safety procedures and products, and build capacity for organizations to respond faster. It is necessary to create and widely disseminate tsunami evacuation or flooding maps, and instructions on when to go, where to go, and how to go. Evacuation shelters and evacuation routes need to be clearly identified and widely known by all segments of the coastal population.
vi. Strong buildings, safe structures, and prudent land-use policies which save lives and reduce property damage that are implemented as pre- disaster mitigations. Tall, reinforced-concrete buildings may be adequate places to which people can vertically evacuate if there is no time to reach higher ground inland. Long-term planning to avoid placing critical infrastructure and lifeline support facilities in inundation zones will reduce the time needed for services to be restored.
vii. Stakeholder coordination as the essential mechanism that facilitates effective actions in warning and emergency response. Clear designation of the national or local authority from which the public will receive emergency information, it is critical to avoid public confusion, which would compromise on public safety.
viii. High-level advocacy that ensures a sustained commitment to prepare for infrequent, high- fatality natural disasters such as tsunamis.