Tsunamis have the same impacts on MEDC’s and LEDC’s.
As seen on Boxing Day 2004, just off the west coast of the Indonesian island of Sumatra, and in March 2011, just off the eastern coast of Japan, earthquakes can have devastating consequences, as can the tsunamis that followed.
Submarine earthquakes are the most common cause of tsunamis (responsible for about three-quarters of all tsunamis), however they are not exclusively causal as they can also be triggered by volcanic eruptions above or below water, landslides (e.g. iceberg calving) or, rarely, meteorite impacts. The quakes are the result of the sudden movement of tectonic plates at subduction zones, where one plate is typically forced under the other at a plate boundary. This sudden shift in the movement of the plates sends a tremendous force upward which is transferred to the water directly above the epicentre. The water column is displaced above sea level and gravity forces the energy out horizontally at the surface, creating a wave with an enormous amount of energy. As the energy is generated by force on the ocean floor (epicentre of the mega-thrust earthquake) the wave can reach speeds of up to 950 km/h while only having a height up to 1m. Out at sea, where the water is deeper, the tsunami may not even be noticeable to passing ships but once it reaches the coast, friction slows it 50 km/h or less. Here, the shallow water compresses the energy causing the wave to concertina, forcing the water upward, creating a tall wall of water (up to 30m high) that inevitably will have a destructive effect as the water rushes over the land.
In order for a tsunami caused by a underwater earthquake to occur, three things have to happen. Firstly, the earthquake must measure at least 7.0 on the Richter scale. Only from this intensity is there enough energy released to rapidly displace enough water to create the tsunami. Next, the sea bed must be lifted or lowered by the earthquake, as seen in the 2011 Tōhoku...
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