One of the most frightening and destructive phenomena of nature
is a severe earthquake and its terrible aftereffects. An
earthquake is the sudden, rapid shaking of the earth, caused by
the breaking and shifting of subterranean rock as it releases
strain that has accumulated over a long time. For hundreds of
millions of years, the forces of plate tectonics have shaped the
earth, as the huge plates that form the earth’s surface slowly
move over, under and past each other. Sometimes, the movement is
gradual. At other times, the plates are locked together, unable
to release accumulated energy. When the accumulated energy grows
strong enough, the plates break free. If the earthquake occurs
in a populated area, it may cause many deaths and injuries and
extensive property damage.