If we look at the pattern of where earthquakes occur
around the world, it is clear that most of the
earthquake activity is concentrated in a number of
distinct earthquake belts. For instance, around the
edge of the Pacific Ocean, or in the middle of the
Atlantic Ocean. These earthquake belts provide an
important clue in the development of the theory of
plate tectonics.
Above: A map of the world's earthquakes shows that
most of them lie in narrow zones, often around the
edges of the continents, or in the middle of the
oceans. Click here to view map as larger image.
The outer shell of the Earth, or Lithosphere, is
made up of a number of rigid segments called
tectonic plates. These plates are continually
moving at rates of a few centimetres per year
(about as fast as your fingernails grow), driven
by forces deep within the Earth. Below the
Lithospheric plates, lies the Earth’s
Asthenosphere. The Asthenosphere behaves like a
fluid over very long time scales, allowing it to
convect. Convection acts like giant conveyor
belts, moving the overlying plates around.
At the boundaries between the plates, where they
are moving together, apart or past each other,
tremendous stresses build up, and are where most
earthquakes occur.
