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CHAPTER 7
EARTHQUAKES
7.1 Notes
What are earthquakes?
• earthquakes - movements or shaking of the
ground when rock (plates) move suddenly
and release energy.
• aftershock – a release in energy after an
earthquake
Where do most earthquakes happen?
On plate boundaries
What causes earthquakes?
• Movement of the tectonic plates
• When the plates break at a fault located at a
boundary
How do we know there are different
layers of the Earth?
• Because of seismic waves from earthquakes
• Seismic waves travel through solids faster than
liquids
• Seismic waves change direction when they change
the material they are going through (from a solid
to a liquid)
• elastic rebound – the sudden return of deformed
rock to its normal undeformed shape. (i.e. rubber
band)
7.1 Notes
•
seismic waves – waves of energy that travel
through and on the Earth
•
2 types of seismic body waves:
1. P-waves (primary waves) – the fastest seismic waves that
travel through solids, liquids, and gases
•
(the P-waves move like a slinky)
2. S-waves (secondary waves) – the second fastest seismic
waves that travel through solids
•
•
(the S-waves move like a snake)
1 type of seismic surface waves :
1. L-waves (land & last waves) – the slowest and most
destructive seismic waves that travel only on the surface/land
•
(the L-waves move in big slow circles)