Tsunamis

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Seeing as the last time I wrote to you guys about Earthquakes I thought today I would write to you about tsunamis which can be a result of an earthquake. Tsunami is a Japanese word that literally means harbour wave.  A tsunami is typically caused by undersea earthquakes. About 80% of the world’s tsunamis happen within the Pacific Oceans “Ring of Fire”. This is the same percentage as earthquakes so you can see how heavily connected the two are.  Tsunamis can also be caused by underwater landslides or volcanic eruptions or even a large meteor impact on the sea. Tsunamis can race across the ocean at about 5000m/hr. which is 805km/hr.!! That is as fast as a jet plane! In the deep ocean tsunamis may only appear at about a foot or two tall but as the approach the shore and enter shallower land they slow down and begin to grow in energy and height.  Before a tsunami is about to hit the water retreats recognizing this unbelievable sight as a warning can save lives. 

How earthquakes cause tsunamisTsunamis occur when an earthquake causes the seafloor to rise and fall. This movement causes a rapid displacement of water; this then causes a wave which as it approaches the coastline its get higher as the seafloor gets shallower causing a tsunami.

How volcanoes cause tsunamisThere are two different ways that volcanoes cause seismic waves.  One possibility is after a volcano occurs on land a large amount of ash and debris into the water causing a sudden change in displacement of water which transfers to kinetic energy which results in waves.  Another way a volcano can cause a tsunami is by submarine volcano collapsing spewing lava and heating the surrounding water quickly.

How Landslides cause tsunamisLandslides are usually caused by earthquakes a tsunami then occurs when a large amount of soil or rocks fall into the ocean disrupting the sea.