Download Earthquakes

Causes of Earthquakes
An earthquake is a shaking of the Earth’s crust cause by a release of energy.
Earthquakes happen because – eruption of a volcano, collapse of a cavern,
impact of a meteor
Most major earthquakes are caused by the movement of two faults (Fault 
a break in the lithosphere {crust} between two lithospheric plates)
Focus ……
The point where the first movement occurs
Epicenter…..
The point on Earth’s surface directly above the focus
Waves
1. Body waves  waves that travel from
the focus of the earthquake through
the Earth
P-waves
P waves  primary waves, compressional waves  squeeze and stretch rock
materials as they pass through Earth; p-waves can travel through any
material….solid rock, magma, ocean water, air
S-Waves
S waves  secondary waves, shear waves  cause particles of rock
material to move at right angles to the direction in which the waves are
traveling; s-waves can ONLY travel through solid material, NOT liquids or
gases
Surface Waves
Earthquake waves that travel along
Earth’s surface.
Love waves  cause particles of material
to move from side to side, in a direction
PERPENDICULAR to the waves’ direction
of travel
Rayleigh waves  travel slower than Love
waves; material moves in a elliptical
pattern
Seismograph
Seismograph
Detects and records waves produced by earthquakes
Magnitude
Strength of an earthquake
Charles Richter (1935)  Richter Scale ;
each level on the scale is 31 times greater
than the level before it
Earthquake Hazards……
Ground shaking and foundation failure (buildings falling over, completely
collapsing)
Liquefaction  loose soil that moves like a liquid instead of a solid
http://www.youtube.com/watch?v=j0sLyJpfTE8
Aftershocks  smaller earthquakes that follow after the main earthquake
http://www.youtube.com/watch?v=Z7eABGpOHv8
Fire
http://www.youtube.com/watch?v=f5xt8oQTApE
Tsunami  underwater earthquakes that create huge ocean waves
http://www.youtube.com/watch?v=k8IAgUNr6x4