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Author(s): Deanne Erdmann, MS, and Nancy Moreno, PhD

What is a Tsunami?

A tsunami is a series of large ocean waves, generally caused by geological disturbances that displace a large volume of water. Radiating like ripples on a pond, tsunami waves can move at incredible speeds for long periods of time. Surprisingly, they can go virtually unnoticed in the open ocean because they may reach a height of only 12 inches or so. As the waves approach shallower water near a shore, they slow and compress, and increase significantly in height.