Forces in Earth

1
Forces in Earths Crust

• Chapter 6 Section 1

2
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

3
Earthquakes

• Elastic limit the most that something can be
  stretched or bent before breaking

4
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)

5
Faults

• the place where rocks break and move by one
  another
• There are 3 types of faults

6
Normal Faults

• Caused by tension forces
• Example Sierra Nevadas

7
Normal Faults
Hanging Wall
8
Reverse Faults

• Caused by compression forces
• Example Himalayas

9
Reverse Faults
Hanging wall
10
Strike-Slip Fault

• Caused by shearing forces
• Occurs at transform boundaries
• Irregular surfaces snag each other
• Example San Andreas Fault

11
Strike-Slip Fault
12
Lets 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
13

• Earthquakes can be dramatic
• or almost unnoticed

14
Changing Earths Surface

• Sometimes plate movements cause the crust to fold
  (mountain building)

15
Changing Earths Surface

• Stretching can cause fault-block mountains

16
Changing Earths Surface

• Large, flat, blocks of rock can be pushed upward
  high above sea-level (plateau)