Earth

1
Earths Crust in Motion

• EQ How do stress forces affect rock?

2
Earthquakes

• Earthquake The shaking that results from the
  movement of rock beneath Earths surface

EQ How do stress forces affect rock?
3

• Two powerful forces that change rock in the
  Earths crust
• Stress
• Friction

4
Stress

• Stress A force that acts on rock to change its
  shape or volume

EQ How do stress forces affect rock?
5
What is Volume?

• The amount of space an object takes up

EQ How do stress forces affect rock?
6

• Energy is stored in rock until the rock either
  breaks or changes shape

EQ How do stress forces affect rock?
7
Shearing

• Shearing Stress that pushes a mass of a rock in
  opposite, horizontal directions

EQ How do stress forces affect rock?
8
Tension

• Tension Stress that stretches rocks so that it
  becomes thinner in the middle

EQ How do stress forces affect rock?
9
Compression

• Stress that squeezes rock until it folds or breaks

EQ How do stress forces affect rock?
10
Figure 2 If shearing continues to tug at the
slab of rock in B, what will happen to the rock?

• The rock will break the two parts will move in
  opposite directions

EQ How do stress forces affect rock?
11
Deformation

• Deformation A change in the volume or shape of
  Earths crust
• Most changes in the crust occur so slowly that
  they can not be observed directly

EQ How do stress forces affect rock?
12
Checkpoint (Page 55) How does deformation change
Earths surface?

• It causes it to
• Bend
• Stretch
• Break
• Tilt
• Fold
• Slide

13
Guide For Reading How does stress forces affect
rock?

• The three kinds of forces that affect rock are
• Shearing
• The rocks break and slip apart
• Tension
• The rock stretches and becomes thin in the middle
• Compression
• The rock squeezes until it folds or breaks
• These stresses work over millions of years to
  change the shape and volume of rock

14
Faults
EQ How do stress forces affect rock?

• A break in the Earths crust where slabs of rock
  slip past each other
• Faults occur when enough stress builds up in rock
• Rocks on both sides of the fault can move up or
  down, or sideways

15
Strike-Slip Faults
EQ How do stress forces affect rock?

• A type of fault where rocks on either side move
  past each other sideways with little up-or down
  motion.
• Shearing causes these types of faults

16
Normal Faults

• A type of fault where the hanging wall slides
  downward
• Tension forces cause normal faults

EQ How do stress forces affect rock?
17
Hanging Wall Footwall

• Hanging wall The block of rock that forms the
  upper half of a fault
• Footwall The block of rock that forms the lower
  half of a fault

EQ How do stress forces affect rock?
18
Reverse Faults

• A type of fault where the hanging wall slides up
• Compression forces cause reverse faults

EQ How do stress forces affect rock?
19
Checkpoint (Page 57) What are the three types of
fault? What force of deformation produce each?

• Strike-slip faults
• Produced by shearing
• Normal faults
• Produced by tension
• Reverse faults
• Produced by compression

20
Why do faults form and where do they occur?

• Plate move and they compress, pull or shear the
  crust so much it breaks
• Faults occur along plate boundaries

21
EQ How do stress forces affect rock?
22
Which half of the reverse fault slid up and
across to form this mountain, hanging wall or the
footwall? Explain.

• The hanging wall slipped up and across. If the
  footwall had moved up, the fault would be called
  a normal fault

EQ How do stress forces affect rock?
23
What is friction?

• A force that opposes the motion of one surface as
  it moves across another surface
• It exists because rocks are not perfectly smooth

EQ How do stress forces affect rock?
24
Describe what occurs when the friction along a
fault line is low.

• The rocks on both sides of the fault slide by
  each other without much sticking

EQ How do stress forces affect rock?
25
Describe what occurs when the friction along a
fault line is moderate.

• The sides of the fault jam together
• From time to time they jerk free
• Small earthquakes occur

EQ How do stress forces affect rock?
26
Describe what occurs when the friction along a
fault line is high.

• Both sides of the fault lock together and do not
  move
• The stress increases until it is strong enough to
  overcome the force of friction
• Larger and/or more frequent earthquakes will occur

EQ How do stress forces affect rock?
27
Fault-Block Mountain
EQ How do stress forces affect rock?

• A mountain that forms where a normal fault
  uplifts a block of rock

28
How does the process of a fault-block mountain
begin?
EQ How do stress forces affect rock?

• Where two plates move away from each other,
  tension forces create many normal faults
• When two of these normal faults form parallel to
  each other, a block of rock is left lying between
  them
• As the hanging wall of each normal fault slips
  downward, the block in between moves upward
• When a block of rock lying between two normal
  faults slides downward, a valley forms

29
Folds
EQ How do stress forces affect rock?

• A bend in rock that forms where part of Earths
  crust is compressed

30
How does the compression of two plates cause an
earthquake?

• The collisions of two plates can cause
  compression and folding of the crust
• Such plate collisions also lead to earthquakes,
  because folding rock can fracture and produce
  faults

EQ How do stress forces affect rock?
31
Anticline

• Anticline An upward fold in rock formed by
  compression of Earths crust

EQ How do stress forces affect rock?
32
Syncline
EQ How do stress forces affect rock?

• Syncline A downward fold in rock formed by
  tension in Earths crust

33
Plateaus

• A large area of flat land elevated high above sea
  level

EQ How do stress forces affect rock?
34
Guide For Reading How does movement along faults
change Earths surface?

• Over millions of years, fault movement can change
  a flat plain into a towering mountain range
• Mountain ranges can form from
• Fault block mountain
• Folding
• Anticlines Synclines
• Plateaus