How Quickly Can a Tsunami Move?

Tsunamis are among the most destructive forces in nature. With little warning, these giant waves can reach heights ranging from 10 feet (3.05 m) to, in extreme cases, 100 feet (30.5 m).

Most tsunamis are caused by undersea earthquakes that occur at the boundaries between tectonic places. When these geologically active areas experience a sudden movement in the ocean floor, the displaced water results in a series of gigantic rolling waves that radiate out from the source. Less frequently, tsunamis are caused by the eruption of undersea volcanoes, underwater landslides, or even large meteorites hitting the ocean.

In the deepest parts of the sea, tsunamis are capable of reaching speeds of around 500 miles per hour (805 km/h) – comparable to the speed of a jet airplane – allowing them to cross vast expanses of ocean in a matter of hours. Remarkably, tsunamis lose very little energy as they travel. Large tsunamis, like the 2004 Indian Ocean tsunami, can travel thousands of miles and cause damage to far-flung countries.

Unlike wind-driven waves that only affect the ocean’s top layer, tsunami waves travel through the entire water column. Interestingly, you might not even notice a tsunami if you were onboard a boat in the middle of the ocean – the top of the wave might only cause a few feet of displacement beyond the water surface. But when tsunamis approach the shallow water close to a shoreline, they finally slow down, their wavelength decreases, and they increase dramatically in height.

The awful, awe-inspiring power of tsunamis: