Transcript Lesson 3

Lesson 3
How do Earthquake Waves Travel?
• Energy released from moving plates and
faults travels through the Earth as waves.
• These waves are called seismic waves.
Types of Seismic Waves
1. BODY WAVES: Seismic waves that travel through the
Earth.
2. SURFACE WAVES: Seismic waves that travel along the
surface.
• WAVES TRAVEL:
1.At different speeds and
2 In different ways
Depending on what kind of material they are
moving through.
Body Waves
• There are two types of body waves:
• P-waves
• S-waves
P-waves
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P-waves are pressure waves.
P-waves travel through solid, liquids and gases.
P-waves are the fastest waves.
P-waves are the first waves to be detected and the first waves to
arrive.
• P-waves are also called primary waves because they arrive first.
• P-waves cause rock to squeeze and stretch. Imagine a slinky!
• The area of the Earth that does not receive seismic energy is called
the shadow zone.
S-waves
• S-waves are the second fastest waves.
• S-waves are also called secondary waves
because they arrive second.
• S-waves are slower than P-waves.
• S-waves move rock from side to side.
• S-waves can’t travel through parts of the
Earth that are completely liquid.
Surface Waves
• Surface waves move along the surface
of the Earth.
• Surface waves can move up, down and
around or side to side.
• Surface waves move the slowest and
cause the most destruction.
Seismic Wave Arrival
• First- P-waves
• Second- S-waves
• Third- Surface Waves
Shadow Zone
The shadow zone results from S waves being stopped entirely by
the liquid core and P waves being bent (refracted) by the liquid
core.
Moho Zone
• The Moho is the boundary between the crust and the
mantle in the earth. This is a depth where seismic waves
change velocity, or speed. They tend to increase at the
location.
Quiz
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1. Most Earthquakes occur along ________________.
2. The first seismic waves to arrive are______________.
3. The second seismic waves to arrive are _____________.
4. The last seismic waves to arrive are_______________.
5. Which seismic waves travel the fastest?___________
6. Which type of seismic wave can move through a solid, liquid or a
gas?________________
• 7. Which seismic wave cannot travel through material that is
completely liquid?______________
• 8. Which seismic waves are the slowest and the most
destructive?_______________