1. Faults-notes and model
Earth Science
Faults-notes and model

2. The movement of Earth’s plates creates enormous forces that squeeze or pull rocks in the crust. These forces are examples of stress, a force that acts on rock to change its shape or volume (the amount of space the rock takes up.) Because stress is a force, it adds energy to the rock. The energy is stored in the rock until the rock changes shape or breaks.

3. Three different kinds of stress can occur in the crust- tension, compression, and shearing. These stresses work over millions of years to change the shape and volume of rock. These forces cause some rocks to become brittle and snap and others to bend slowly.
Tension-stress that stretches a rock so it becomes thinner in the middle. (ex. Pull a fresh Tootsie Roll from each end and what happens?)

4. Compression-stress that squeezes a rock until it folds or breaks. (ex
Compression-stress that squeezes a rock until it folds or breaks. (ex. Take a fun size Milky Way and push it inward from both sides, what happens?)
Shearing-stress that pushes masses of rock in opposite directions, in a sideways movement. (ex. Take Tootsie Roll or Milky Way and move each side in opposite directions, what happens?)

5. The Basics What is a fault?
a break or crack in the Earth’s crust along which movement has occurred
What is a fault plane?
the surface that separates the two moving sides

6. Faults are often, but not always, found near plate boundaries
Faults are often, but not always, found near plate boundaries. Each type of fault is often related to specific types of plate movements.
You remember…convergent collide, divergent divide, and transform slide! Let’s add some movements into that little diddy.

7. There are two categories of faults.
Dip-Slip Faults
Normal faults are often associated with divergent (tensional) boundaries.
Reverse faults are often associated with convergent (compressional) boundaries.
Strike-Slip Faults
3. Strike-slip faults are often associated with transform (sliding/shearing) boundaries.

8. Fault Plane-the plane that represents the fracture surface of a fault
Hanging wall
Footwall
Fault Plane-the plane that represents the fracture surface of a fault

9. The stresses and strains in the Earth’s upper layers have many causes: thermal expansion and contraction, gravitational forces, solid-earth tidal forces, specific volume changes because of mineral phase transitions, and the list goes on.
Faulting is one of the various manners of mechanical adjustment or release of such stress and strain.

10. You have made a fault model for us to use in illustrating the three types of faults. Using a pair of scissors, cut your fault model along the dotted line.
MAKE SURE YOUR NAME IS ON BOTH HALVES OF YOUR MODEL.
We are ready to begin…

11. Modeling the Faults:
Normal Fault-occurs when the rocks on one side of the fault plane drop down with respect to the rocks on the other side
Locate points A and B on your model.
Move point B so that it is next to point A.
Observe your model from the side.
Draw and color the normal fault as you see it from the side.

12. Fault Animations
Normal Fault Animation
US Geologic Survey

13. Modeling the Faults:
Reverse Fault (aka Thrust Fault)-result in larger earthquakes than strike-slip faults; tend to occur in the ocean at subduction zones
1. Locate points C and D on your model.
2. Move point C next to point D.
3. Observe your model from the side.
4. Draw and color the reverse/thrust fault as you see it from the side.

14. Fault Animations
Reverse Fault Animation
US Geologic Survey

15. Modeling the Faults:
Strike-Slip Fault-when opposing forces cause rocks to break and move horizontally
1. Locate points F and G on your model.
2. Move the pieces so that point F is next to point G.
3. Draw and color an overhead view of the surface of your model, as it looks after the movement along the fault.

16. Fault Animations
Strike Slip Fault Animation
US Geologic Survey

17. Putting it all together
A great video summary!