The study of the thin outer layer of the earth from deep sea to shallow waters is referred to as marine science. Marine science studies ocean geology, chemistry, biology, and physics making it a productive interdisciplinary science. The oceans cover two-third of the earth’s surface and are dynamic, it contains most surface heat, carbon, and earth's water but it is interdependent with the cryosphere (ice), and continents are driven by energy derived from the interior of the earth and the sun. Marine scientists focus on basic scientific questions and both applied & practical problems. The oceans provide a variety of food, water reservoir, and they are the source of heat and carbon used in the climate system. The thin shell is the source of half the oxygen the biosphere needs. The oceans are the source of massive storms, hurricanes, and transmit energy over a long distance known as tsunamis. Ocean poses a threat to the coastal residents and are necessary for a fraction of the earth's population
A tsunami is a series of ocean waves triggered by an underwater landslide, a high magnitude volcanic eruption, or an earthquake. Rarely a tsunami is caused by meteor impact with ocean water. Tsunami waves can travel to heights over a hundred feet. The time that the waves take to reach the coastal shore is referred to as the wave period and is approximated to be between five minutes and an hour or two. The first wave rarely causes destruction and is not the strongest and dangerous; however the fifth or sixth are usually large waves. The subsequent waves are more dangerous and carry debris deposits, people, and destroy property at the shores of the ocean. Thucydides, a Greek historian, was the first person to associate tsunami with underwater. Tsunamis are 1 to 3 feet tall in deepest ocean basin and sailors may fail to notice the tsunami waves passing beneath them. Fatal tsunami cases had occurred within a radius of 250 kilometers from the epicenter or within a period of 30 minutes when the tsunami struck. Often when a tsunami wants to attack, ocean water seems to be drawn back to the ocean basin to a maximum of half an hour before it strikes. Anyone at the coastal shores should take this as a natural warning, any time one feels a strong earthquake he/she should leave the low-lying places to a raised ground. Examples of states in the United States that are at risk of being struck by the tsunami include Alaska, California, Oregon, Hawaii, and Washington (Mimmura et al. 2012).
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The most catastrophic earthquake to ever hit the earth occurred in India in 2004, and it struck ten other countries from Africa to Thailand and the rest of the world. The phenomenon resulted in the loss of property of immense value, and approximately over two hundred thousand lives were lost. The massive loss of lives includes that of both locals and tourists. Nine thousand tourists from Sweden, Australia, U.S. and United Kingdom, France, and Germany had visited Southeast Asian countries such as Malaysia to celebrate the Christmas festival season lost their lives. The tsunami had a magnitude of 9.0 from the epicenter. Interestingly, most animals are reported to have escaped the disastrous outcome of the 2004 India tsunami. Most of the animals moved to higher grounds.
Earthquakes generated by tsunamis are created along subduction zones meaning the heavy plate tectonics overrides the lighter plates. Whenever the oceanic plates rise, or fall displaces the entire overlying water column. The rise and fall of tectonic plates above the ocean floor earthquake triggers the tsunami. The movement of plates along or away from each other cannot cause a tsunami. The most destructive tsunamis are caused by shallow earthquakes with a fault line on the ocean floor. When the tectonic plates and oceanic plates override each other, they result into high magnitude earthquakes and this tilt the ocean displacing bigger size of the ocean from one to thousands of kilometers. The rapid vertical displacement of water triggers destructive tsunami waves that move across the ocean and towards the shore. The tsunami wave can spread destruction along the way and can travel for a very long distance. A good example of this type of tsunami is the great Chile tsunami triggered by a magnitude of 9.5 on Richter scale. The tsunami wave moved over a thousand kilometers, and these waves caused destruction not only in Chile but also in Japan, Hawaii, and some other Pacific regions.
Interesting facts about tsunami
Scientists have proven that tsunamis move at a speed of nine hundred kilometers per hour. The rate is calculated, to predict the most likely areas to be struck by the tsunami waves. The speed is equivalent to that of a jet plane. Regular water moves at two to sixty miles an hour, unlike tsunami. Tsunamis retain their energy enabling them to make progress across the ocean without losing power. A teletsunami is a tsunami that moves along the ocean covering a larger area on the water surface. A local tsunami is one that reaches the coast that is its epicenter. Whenever a tsunami approaches the shore, it slows down. As the water reduces in speed, all the water that was traveling at a greater speed pulls up resulting the wave to grow bigger and bigger. A tsunami can be 100 feet high or can be the height of a ten-storey building by the time the waves hit the shore. Some people refer tides to tsunamis which are misleading because tsunamis are different from tides. Tsunami waves look like a wall of water and not a normal ocean wave. Tsunami wave do not break and curl as they come so rapid such as floods of water or in the shape of a bore (Suppasri et al. 2012).
The 2011 Japan earthquake that triggered the tsunami is the fifth largest since the year 1900. Many people were evacuated after the tsunami; the number is approximated to be over 180,000 people. The estimated number of dead people was around ten thousand, seventeen thousand four hundred and forty were missing, and two thousand seven hundred and seventy-five people were injured as of March 25 th , 2011. The same tsunami is perceived to be the most expensive disaster to have occurred in the world. The wave damaged generators and the primary cooling system at Fukushima Daiichi nuclear complex in Japan. Recovery of the Japan tsunami-affected areas is estimated by the World Bank at $232 billion and will take a minimum period of five years to rebuild. Due to the long, devastating history of tsunamis in Japan, she has the most advanced tsunami warning system in the world before the wave struck. The system consists of five hundred water-level gauges and more than a thousand five hundred seismometers. The system costs $20 million a year to operate. Some geologists have argued that the ancient tsunamis are the real source of ancient legends. For example, the opening of the red sea during the Israelites exodus from Egypt a land they had been slaves for 400 years is attributed to tsunamis. The great biblical flood story of Noah, who preached for 120 years but never got a single convert, is also attributed to the ancient tsunami.
After the destruction, property destroyed is recovered during reconstruction probably by getting newer or even better substitute compared to the initial ones. After reconstruction, the initially vulnerable victim country prevents and mitigates the risks. Besides, the affected countries end up being wealthier than they were before the disaster struck. Plate tectonic movement naturally cycles valuable materials from the interior of the earth out to the exterior. Earthquakes are necessary for causing tsunami and availing some plants that are vital in the ecosystem that without them the ecosystem would have been no balance (Morgan et al. 2006).
Unanswered question
Geologists and Geophysics in the twenty-first century are trying to focus on foreseeing catastrophic phenomena such as earthquakes, landslides, and volcanic eruptions that pollute and degrades the environment. Currently, most questions about the causes of tsunamis and earthquake prone regions have been answered to a bigger scale. The biggest worry is how to predict and evacuate people in tsunami prone areas to save lives and reduce the number of deaths before the disaster has stricken (Västfjäll, Peters, & Slovic 2008).
Some of the question includes
How can tsunamis and earthquakes be predicted? There is a little understanding of how tsunamis and earthquakes occur. Tsunamis have occurred at the United States east coast.
Another question is; is it possible for the tsunami to occur on the eastern shore of the U.S. or any other unsuspected areas?
Is it possible that marine minerals extraction can cause instability on the floor of the ocean and trigger tsunamis?
Why? Some submarine earthquakes trigger destructive tsunamis while others do not generate tsunami waves.
Can stress changes caused by earthquakes retard or hasten the onset of later earthquakes?
Is it possible to drill into the earth’s mantle? Earlier attempts failed like in the Mohole project.
Lastly; Is it possible to predict volcanic eruptions?
References
Morgan, O. W., Sribanditmongkol, P., Perera, C., Sulasmi, Y., Van Alphen, D., & Sondorp, E. (2006). Mass fatality management following the South Asian tsunami disaster: case studies in Thailand, Indonesia, and Sri Lanka. PLoS Med, 3(6), e195.
Västfjäll, D., Peters, E., & Slovic, P. (2008). Affect, risk perception and future optimism after the tsunami disaster.
Suppasri, A., Mas, E., Koshimura, S., Imai, K., Harada, K., & Imamura, F. (2012). Developing tsunami fragility curves from the surveyed data of the 2011 Great East Japan tsunami in Sendai and Ishinomaki plains. Coastal Engineering Journal, 54(01), 1250008.
Mimura, N., Yasuhara, K., Kawagoe, S., Yokoki, H., & Kazama, S. (2011). Damage from the Great East Japan Earthquake and Tsunami-a quick report. Mitigation and Adaptation Strategies for Global Change, 16(7), 803-818.
