An earthquake is caused by the sudden movement of parts of the Earth's crust and results in shaking and trembling of the ground. There are over one million earthquakes each year, with around twenty having the potential to cause severe damage. Earthquakes are caused by faults in the Earth's crust, such as the San Andreas Fault in California where the land west of the fault moves north and the land east moves south. Underwater earthquakes can generate destructive tsunamis. The focus is the depth below the surface where the earthquake occurs, and the epicenter is directly above on the surface. Seismographs detect seismic waves that travel out from the epicenter, including fast P waves and slower S waves.

2. Earthquake
– is the shaking
a trembling that results from
the sudden movement of
part of the Earth’s crust.

3. http://www.youtube.com/watch?v=ca
vq2HFBa-U&feature=fvsr

4.  One
million earthquakes happen in a
year
 one thousand every year makes the
earth move
 twenty can cause severe damage.

5. Faulting causes earthquakes.
San Andreas Fault – land to the
west is moving north and the land to
the east is moving south

8.  Tsunamis – earthquakes that occur
on the ocean floor produce giant sea
waves called tsunamis.

9.  Focus – the point beneath the
Earth’s surface where the rocks break
and move.
 Epicenter – directly above the
focus, on the Earth’s surface

11. Also known as Earthquake Waves

12. Fastest waves
P waves
Moves through
solids, liquids, and gases
Speeds up in denser
material
Push and pull waves

13. S waves
Slower than P waves
Travels through solids but
not liquids and gases
Speeds up in denser
material
Movement is side to side

14. 

S waves: do "the wave" as they would
in a football stadium, raising their arms
and lowering them as the next person
raises his or hers.
P Waves: gently grip each other's
shoulders and having one pull or push
the next person in line.

15. L waves
Slowest waves
Originates at the epicenter
Creates the wave
movements in the Earth’s
surface
Causes the most damage

16.  Seismograph – is an instrument
that detects and measures
seismic waves
 Seismologist – scientists who
study earthquakes, can
determine the strength of them