Page 26 - Super Earth Encyclopedia

EARTHQUAKES

Nearly all earthquakes occur on the boundaries
between the mobile plates of Earth’s crust. These
plates are always moving, but the boundaries rarely
move at the same steady rate. The rocks become
locked together, and the strain builds up until
they suddenly give way, causing an earthquake.
If this happens on the seabed, it can
trigger a tsunami.

This plate of Earth’s crust
is moving very slowly,
but its edge has locked
against another plate.

SHOCK WAVE
When a boundary between
moving plates keeps slipping, it
causes minor tremors. But if the
boundary is locked, the edges of
the plates get distorted like bent
springs. When the rocks give way,
all the movement that should
have occurred over many years
happens within a few minutes,
generating the shock wave we An earthquake is caused by The point where the fault Most damage occurs
call an earthquake. a sudden movement of the has given way is the focus directly above the
fault line where the plates of the earthquake. It is focus. This is called
slide past each other. deep under ground. the epicenter.

DESTRUCTIVE FORCE
Although most earthquakes
last only a few minutes, they
can be devastating. Some of
the damage may be the result
of movement of the rocks
along a fault line. But most
of the destruction is caused
by the shock waves that travel
out from the focus of the
earthquake. These can shake STRUCTURAL COLLAPSE LANDSLIDES FIRES
the ground with such Shaking ground makes brick or stone In hilly regions, rock and soil can be Earthquakes that hit cities often fracture
violence that anything built buildings crumble and collapse. Even loosened by an earthquake and surge gas pipes, oil tanks, and electrical cables,
on it is certain to collapse. steel-framed buildings can topple as downhill in a landslide. If this hits a causing fires. These can result in far more
the ground shifts beneath them. town, it can have devastating effects. damage than the earthquake itself.

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