How do tsunamis travel across entire oceans?
Quick Answer
They are very long-wavelength waves caused mainly by seafloor displacement, often from undersea earthquakes. In deep water they can travel around 700–800 km/h and grow much taller near shore.
The Full Story
A tsunami begins when a large volume of seawater is suddenly displaced, most commonly by a megathrust earthquake at a subduction zone. Unlike wind waves, a tsunami involves the entire water column, so it can move very fast in deep ocean with little visible height. As it reaches shallower water, the wave slows down and its energy is compressed upward, producing a dangerous surge. Historic tsunamis have crossed whole ocean basins and caused devastation far from their source.
Key Facts
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