Download Chapter 6 Lesson 1

Chapter 6 Lesson 1
Plate Boundaries & Earthquakes
Type of Boundary
Description of Movement
Description of Earthquake
Divergent
Pulling apart of stretching
Shallow; relatively small in size
Convergent
Pushing Together
Deep; largest earthquakes ;
historically they have been the
most destructive earthquakes
Transform
Scrape past one another
Shallow; major earthquakes on
continents
shallow focus produces severe
shaking- that is what causes
dangerous earthquakes to occur
Earthquakes Away from Plate
Boundaries
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Some earthquakes occur away from plate boundaries
So, they will unexpectedly happen in the middle of continents & they can be
dangerous
Chapter 6 Lesson 2
What are Seismic Waves?
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These are the waves of energy that are produced at the
focus of an earthquake
How do they travel?
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seismic waves move outward from the focus in all
directions
an earthquake epicenter is the point on Earth’s surface
directly above the earthquake focus
Types of Seismic Waves
1.P-Waves
• compressional waves that move rock parallel to the direction the wave is
moving
• fastest seismic waves
2.S-Waves
• shearing waves that move rock back and forth perpendicular to the direction
the wave is moving
• about 60% as fast as P-waves
3.Surface Waves
•energy (from the p- and s-waves) that get trapped in the upper areas of Earth's
crust
•slowest type of seismic wave
•usually cause stronger shaking than p-and s-waves (often most destructive type of
wave)
Using Seismic Wave Data
• Speed of Seismic Waves
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S-wave is always behind P-wave
Surface wave arrives last
• Path of Seismic Waves
the different paths each wave
takes, causes them to come
reach us faster or slower
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• Mapping Earth’s internal surface
the densities of rock increase with
depth as pressure increases.
This makes the paths of the waves
change as they pass through Earth
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