A tsunami is a fast moving ocean wave or a series of wave. In the deep ocean, a tsunami is usually no more than one meter tall. When a tsunami reaches shallow water, it can grow as high as 30 meter.
An underwater earthquake, a volcanic eruption, or a landslide can trigger a tsunami. For example, when earthquake happens, the sea floor shifts. This sudden movement creates a sea bulge that send out a series of ripple-like wave. In the deep ocean, these ripples are very wide and low, and travel fast. They cannot be felt aboard ships, nor can they be seen fron the air in the open ocean.
A chain of tsunami wave can be very destructive.
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