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How do earthquakes have anything to do with why tsunamis happen?
Question Date: 2014-05-07
Answer 1:

Great question! Devastating tsunamis often occur immediately after large earthquakes. So, what’s the relationship? It’s actually quite simple. When an earthquake occurs in the crust (the hard plates of rock that cover the earth) beneath the ocean, it sometimes displaces part of the seafloor. What this means is that when the crust breaks, the seafloor can move up, down, or side to side (or a combination of these). When the seafloor moves up or down, it displaces water, meaning that it basically pushes it out of the way. Big earthquakes can move very large parts of the seafloor, pushing away HUGE volumes of water. The energy of that water being pushed aside can cause a tsunami. This doesn’t mean that the water that is pushed aside travels all the way across the ocean, eventually breaking on land. It is actually wave energy that is traveling through the ocean, moving water as it goes. When the wave energy reaches the edge of the ocean it can cause huge waves of water to break onto land.

Sometimes tsunamis are mistakenly called “tidal waves”. They don’t actually have anything to do with tides. They are caused by displacements of the seafloor during earthquakes.

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