Tsunamis are caused by sudden shifting of the ocean floor due to earthquakes, volcanic eruptions and submarine slumping. In other words, tsunamis are long wavelength, shallow water progressive waves caused by the displacement of ocean water. In the open ocean, tsunamis have short wave heights, with long wavelengths reaching a distance of more than 100 km and have long wave periods.
Generally, tsunamis are generated by for major mechanisms. The most common type would be the abrupt deformation of the seabed due to tectonic earthquakes along subduction boundaries. When any tectonic earthquakes cause a shift in the boundaries, there will be a major displacement of the ocean, releasing a huge amount of energy. This energy will be transferred to the water in the form of waves and when this energy filled waves reached the shore and breaks, all the energy is released onto land resulting in major destruction.
The other form of mechanism causing a tsunami is submarine landslides which is earthquake triggered. One example is the Storegga Slide which happened 8000 years ago on the Norwegian continental margin which seriously affected the north-east of Scotland. Volcanic sector collapse is another mechanism which can result in the formation of tsunami. When a volcanic sector collapses, displacement of the land is massive and when this takes place high pressure is involved and transferred between water molecules resulting in the formation of tsunami. Volcanic sector collapse has happened many times in the Canary Islands and is postulated for the Cumbra Vieja volcanic edifice on the La Palma.
Finally is the explosive volcanism with subsequent water inrush and vaporization. This is also another way tsunami will take place. In fact, tsunamis do not actually happen if all of this mechanism happens. In order for a tsunami to form, the energy released with the occurrence of these mechanisms must be very abrupt and extremely high. When this happens, the possibility for tsunami to occur is greater. Examples of explosive volcanism is as what happened in the caldera during major eruptions such as Krakatao and Tambora. Nowadays, due to development, coastal areas have been cleared off. This is also related to the fact that people prefer living by the seaside, away from all sorts of pollution. In order to satisfy the needs of the society, mangroves areas too are being cleared rapidly. Mangrove forest indeed is very useful to the coastal zone as well as society. For instance, mangrove forests are very productive, providing food and shelter to many species of marine as well as terrestrial organisms. Apart from this, mangrove forests help to reduce coastal erosion and by trapping excess sediment and nutrient, reduce coastal pollution. Even the shrimp mariculture, a major booming operation in Southeast Asia, South America and other subtropical and tropical shores, is closely related to the mangrove forest. Sad to say, the mangrove forest is being cleared up at an alarming rate to provide space for crops, development, to be used as fuel and timber. Once, covering up to 75% of the coastal zones, only half remains. The importance of the mangrove forests were not realized until the December 26, 2004 incident when tsunami struck causing massive destruction involving several countries of the Southeast Asian region as well. The mangrove forest wherever still existed and not being exploited clearly proves its role as the primary protection of the inland when the rate of death at locations surrounded by mangroves were many times lesser than areas exposed to the sea. Surveys were carried out to prove this fact, and the aftermath of the tsunami attack showed that the statistics of death in areas with and without mangrove had a great difference with lesser death and even property loss in areas with mangrove.
Apart from mangrove forests, coral reefs too play a vital role in being a form of protection to the shore. As waves travel by transfer of energy and cannot be detected until it reached the shore with shallow depth, coral reefs act as a form of barrier. If a coral reef is located at a distance from land and if huge waves pass it, there is a tendency for the wave to actually break before it reached shore. This is because, the coral reef reduces the depth of the ocean, increasing the wave height and causing the wave to break and lose its energy before reaching the shore. Though this is a fact that coral reefs act as a protection to the shore, the reefs are still threatened by human activities all over the tropics. More than a quarter of the world’s coral reefs have already been lost or are at high risk. Though coral reefs protect the inland, support luxuriant life that provides much needed protein and potentially life saving drugs, they are subjected to various anthropogenic stresses. Therefore, mangrove forests, coral reefs and any other coastal resources should be conserved with great importance as these live forms act as primary protection to the shore apart from their main role to human. Everyone has to play their part in ensuring that these resources are not demolished to satisfy the greed of construction in the name of development.