Tsunamis are often called tidal waves, but this is not an accurate description because tides have little effect on giant tsunami waves.
Far out in the ocean, tsunami waves don’t get very high, but they move very fast. In fact, the National Oceanic and Atmospheric Administration (NOAA) reports that tsunami waves can travel as fast as a jet plane.
As a tsunami gets closer to land and the ocean depth decreases, the speed of the tsunami wave slows down and the height of the tsunami wave increases dramatically—along with its potential for destruction.
One thing is certain about tsunamis: they are unpredictable. Once a tsunami makes landfall, the waves can last from five to 15 minutes and do not follow a set pattern. NOAA warns that the first wave may not be the largest.
Not all undersea earthquakes or other seismic events create tsunamis, which is why tsunamis are difficult to predict.