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Earthquakes at Sea
Earthquakes at Sea
Remember that most earthquakes occur along the boundaries of tectonic plates. Several plate boundaries
are in the ocean, so many earthquakes occur in the oceanic crust that forms the seafloor. This is
especially true around the Pacific Ocean. The Pacific has many deep ocean trenches along the edges of
its ocean basin. Ocean trenches form where one tectonic plate is sliding, or subducting, beneath another
plate. Earthquakes are very common in the continental crust along ocean trenches.
Earthquakes that occur in the crust forming the ocean bottom can cause the seafloor to shift. This shift
can cause seawater, from the ocean bottom to its surface, to suddenly start to move. The result is a
gigantic wave called a tsunami.
Tsunamis travel fast-as much as 500 miles per hour. Out in deep water in the middle of the ocean, you'd
hardly notice this great pulse of water passing by. All that water piles up as the tsunami approaches a
coastline. It becomes a towering wall of water that may be as tall as a three- or four-story building. The
tsunami crashes onto the shore with incredible force. It surges far inland. Then it goes roaring and
churning back out to sea. Tsunamis can cause terrible destruction.
While scientists cannot predict earthquakes, they are able to give some warning for
tsunamis. Depending on its starting point, a tsunami may take many minutes, even
hours, to reach land. Several countries have set up tsunami warning systems in the
Pacific and other oceans.
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