is a series of ocean waves generated by any rapid
large-scale disturbance of the sea water. Most tsunamis
are generated by earthquakes, but they may also be
caused by volcanic eruptions, landslides, undersea
slumps or meteor impacts.
The waves radiate outward in all directions from the
disturbance and can propagate across entire ocean
basins. Tsunami waves are distinguished from ordinary
ocean waves by their great length between peaks. The
speed at which tsunamis travel depends on the ocean
depth. A tsunami can exceed 500 mph in the deep ocean
but slows to 20 or 30 mph in the shallow water near
In the deep ocean, a tsunami is barely noticeable and
will only cause a small and slow rising and falling of
the sea surface as it passes. Only as it approaches land
does a tsunami become a hazard. As the tsunami
approaches land and shallow water, the waves slow down
and become compressed, causing them to grow in height.
In the best of cases, the tsunami comes onshore like a
quickly rising tide and causes a gentle flooding of
low-lying coastal areas.
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