Download Forces in Earth`s Crust

Forces in Earth’s Crust
Chapter 6 Section 1
Earthquakes
Which is more elastic…
a bouncy ball or a bowling ball?
• Elasticity is the ability for an object to
return to or keep its original shape
Earthquakes
• Elastic limit – the most that something can
be stretched or bent before breaking
Earthquakes
• Tectonic movements supply the force that
bend and stretch rocks
• When the elastic limit of rock is passed, it
breaks and produces forces called
earthquakes.
• 80% of all earthquakes occur along edges
of the Pacific Plate (Ring of Fire)
Faults
• the place where rocks break and move by
one another
• There are 3 types of faults
Normal Faults
• Caused by tension forces
• Example: Sierra Nevadas
Normal Faults
Reverse Faults
• Caused by compression forces
• Example: Himalayas
Reverse Faults
Strike-Slip Fault
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•
•
•
Caused by shearing forces
Occurs at transform boundaries
Irregular surfaces snag each other
Example: San Andreas Fault
Strike-Slip Fault
Let’s Review
• What are the 3 kinds of faults?
– Normal
– Reverse
– Strike-slip
• What are the 3 kinds of forces that cause faults?
• At what boundaries do they form?
– Tension
– Compression
– Shearing
Divergent
Convergent
Transform
Earthquakes can be dramatic
or almost unnoticed
Changing Earth’s Surface
• Sometimes plate movements cause the
crust to fold (mountain building)
Changing Earth’s Surface
• Stretching can cause fault-block
mountains
Changing Earth’s Surface
• Large, flat, blocks of rock can be pushed
upward – high above sea-level (plateau)