• Sara Thompson

What Causes Tsunamis?


By Sara Thompson

Special to the Enterprise

A graphic showing three stages of how a tsunami is formed
How a tsunami is formed.

Tsunamis are one of many natural disasters that can impact our planet. It is a giant wave, or series of waves, that can spread water nearly one mile inland. They are triggered by a variety of events and are almost impossible to predict. Scientists have developed ways to detect them and set up warning systems, but they are still working on bettering these systems.


A tsunami itself is a major event, but they do not come from nowhere. Each one is triggered by another source. 70-80% of all tsunamis are caused by earthquakes. Other causes include landslides, volcanic eruptions, meteors, and more. When an earthquake occurs it causes a disturbance in the seafloor, which releases energy. The energy release can cause the water to displace and ripple away from its natural equilibrium. The displacement will continue to travel away from the disturbance, taking up the entire water column instead of just the surface as wind driven waves do. As the wave travels, it can remain undetected in deep water, but as the wave reaches shallower water, the displacement remains much of the same, drawing in more water and generating the famously large waves that reach land. Most tsunamis are less than ten feet high when they reach land, but some can reach over 100 feet in extreme cases.


What makes tsunamis so dangerous is how fast they are and the near impossibility of predication. In the deep ocean a tsunami can travel up to 500 mph, but slow to around 20-30mph as it approaches land. When a tsunami reaches land it causes almost immediate flooding along the shoreline that can reach upwards of a mile inland, depending on the size of the wave. Just a rise in six inches can knock an adult over, with rises upwards of 12 inches or more can carry a small car. When the water recedes back to the ocean it carries much of the debris back with it. Some tsunamis are a “one and done” event, others can produce several waves that can last hours or days.


Although impossible to predict, scientists are developing ways to detect tsunamis. The National Oceanic and Atmospheric Administration, NOAA, has developed a system to detect any wave displacements in the deep ocean that can help alert to the possibility of a tsunami. Although this and other methods are still being developed, they have helped in warning those in the pathway of a tsunami to evacuate before the waves reach land. There is still more research to do to help us to further predict these destructive forces, but scientists will continue to search for these answers until they are solved.


 

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