Earth and Space Science / Unit 4: Earthquakes and Volcanoes
4.1 Stress and Faults
Notes
Rocks are under stress (force on rock). Rock can bend (fold) or break (fault).
- Compression squeezes, tension pulls apart, shear pushes in opposite directions.
- A fault is a fracture where rock has moved. Blocks are the hanging wall (above the fault) and footwall (below).
- Normal fault: hanging wall moves down; caused by tension.
- Reverse fault: hanging wall moves up; caused by compression.
- Strike-slip fault: blocks slide horizontally; caused by shear.
Practice
Tension in the crust most often causes which fault?
Pulling apart lets the hanging wall slide down.
The San Andreas Fault, where blocks slide sideways past each other, is a:
Shear stress gives horizontal motion.
On a reverse fault the hanging wall moves:
Compression pushes the hanging wall upward.
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