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FORCES IN EARTH’S
CRUST
STRESS
Tension
Compression
Shearing
These forces work over millions
of years to change the shape
and volume of rock.
TENSION
Stretches, or pulls the rock apart.
Similar to pulling apart a piece of
chewing gum.
COMPRESSION
Squeezes rock until it folds or breaks.
Similar to a trash compactor.
SHEARING
Pushes rock in two opposite directions.
FAULTS
When enough stress builds up in a rock, the rock
breaks, creating a fault.
Fault- a break in the rock of the crust where rock
surfaces slip past each other.
Most faults occur along plate boundaries,
where the forces of plate motion push or
pull the crust so much that the crust
breaks.
FOOT VS. HANG
FOOTWALL
Block of rock that
forms the lower half
of a fault.
HANGING WALL
Block of rock that
forms the upper half
of a fault.
NORMAL FAULTS (CLICK)
Caused by
TENSION.
The hanging wall
slides downward
as a result of the
rock being pulled
apart.
NORMAL FAULTS
Occur where
plates diverge,
or pull apart
(TENSIONS).
Rio Grande rift
valley in New
Mexico.
NORMAL FAULT QUESTION
How does a normal fault occur?
What type of force causes a normal
fault?
What happens to the footwall and
hanging wall?
REVERSE FAULTS (CLICK)
Caused by
COMPRESSION.
A fault where the
hanging wall slides
upward as a result of
compression.
REVERSE FAULTS
Northern Rocky
Mountains
REVERSE FAULT QUESTION
How does a reverse fault occur?
What type of force causes a reverse
fault?
What happens to the footwall and
hanging wall?
STRIKE-SLIP FAULTS (CLICK)
Caused by SHEARING.
A fault in which rocks on either side move
past each other sideways with little up or
down motion.
STRIKESLIP FAULT
Transform
Boundary- San
Andreas fault
STRIKE-SLIP FAULT
QUESTION
San Andreas fault
Describe how a strike-slip
fault occurs. What force
cause it?
EXAMPLE #1
WHAT TYPE OF FAULT?
WHAT TYPE OF STRESS?
EXAMPLE #2
WHAT TYPE OF FAULT?
WHAT TYPE OF STRESS?
EXAMPLE #3
WHAT TYPE OF FAULT?
WHAT TYPE OF STRESS?
EXAMPLE #4
WHAT TYPE OF FAULT?
WHAT TYPE OF STRESS?
EXAMPLE #5
WHAT TYPE OF FAULT?
WHAT TYPE OF STRESS?
A
B
C
EXAMPLE #6
A
WHAT TYPE
OF FAULT?
WHAT TYPE
OF STRESS?
B
C
FOLDING EARTH’S CRUST
Anticline- a fold in rock that bends
upward into an arch.
FOLDING EARTH’S CRUST
Syncline- a fold in rock that bends
downward to form a valley.
DESCRIBE THE
DIFFERENCE
BETWEEN AN
ANTICLINE AND
SYNCLINE.
WHICH LETTER IS AN ANTICLINE?
WHICH LETTER IS A SYNCLINE?
A
B