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What is a Tsunami?
A Tsunami (pronounced soo-nahm-ee) is a series of huge waves that happen after an undersea disturbance, such as an Earthquake, volcanic eruption or meteorite strike. The word Tsunami comes from the Japanese word for harbour wave. The waves travel in all directions from the area of disturbance, much like the ripples that happen after throwing a rock into the water. The waves may travel in the open sea as fast as 450 miles per hour. As the big waves approach shallow waters along the coast they grow to a great height and smash into the shore. Far out at sea they might not seem more than an average size wave but as they get closer to shore the power it unleashes increases. Tsunami’s can be as high as 100 feet. They can cause a lot of destruction on the shore and can reach far inland. As they hit the shore and head inland they become a massive moving wall of sludge and debris from everything they have already destroyed. They have a force that is so massively powerful anything in it’s path stands little chance of surviving. They are sometimes are mistakenly called ‘tidal waves’, but Tsunami have nothing to do with the tides.
The video below shows various Tsunami’s in action.
Why does a Tsunami happen after some earthquakes?
As it says above, there are different reasons that might make a Tsunami occur but what we are going to try and understand here is how a Tsunami happens after an Earthquake under the sea.
The planet is made up of many plates that fit together like a massive globe wide jigsaw and move constantly at a slow speed. The Science of these plates is called Plate Tectonics.
Watch the video below as it explains how the Tectonic Plates work.
The beginings of a Tsunami.
So pressure builds up at the edge of the meeting plates (which is called a fault line) and eventually builds up to a point where something has to give and one plate moves above or below another. It is at this point when the sudden drop or rise in the plate’s occurs, that the Tsunami is born. The sudden drop or rise in the plate’s creates a massive and sudden shift of the ocean creating the deadly Tsunami wave.
Certain areas of the world are much more likely to experience Earthquakes and these points, in general, are the areas where two Tectonic plates meet. So if you have an area where two Plates meet under the sea, you have a recipe for a Tsunami. In general, the bigger the Earthquake, the bigger the Tsunami wave!
Certain Countries are so used to experiencing frequent Earthquakes that they train their children from a very young age as to how to react and keep safe in one and have warning systems in place. Japan, for instance, also builds coastal defences in areas that are most at risk from Tsunami’s – strong, high walls along the coast and large trees planted near the shore to absorb some of the power of the incoming wave.