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Title: Inside Earth: Chapter 2- Earthquakes Section 1: Earth s


1
Inside Earth Chapter 2- Earthquakes
  • Section 1 Earths Crust In Motion

2
Guide For Reading
  • How does stress forces affect rock?
  • Why do faults form and where do they occur?
  • How does movement along faults change Earths
    surface?

3
Earthquakes
  • Earthquake The shaking that results from the
    movement of rock beneath Earths surface

4
Earths plates create powerful forces that ___ or
___ the rock in the crust.
  • squeeze
  • pull

5
Stress
  • Stress A force that acts on rock to change its
    shape or volume

6
What is Volume?
  • The amount of space an object takes up

7
Energy is stored in rock until the rock
______________.
  • either breaks or changes shape

8
Shearing
  • Shearing Stress that pushes a mass of a rock in
    opposite, horizontal directions

9
Tension
  • Tension Stress that stretches rocks so that it
    becomes thinner in the middle

10
Compression
  • Stress that squeezes rock until it folds or breaks

11
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

12
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

13
Checkpoint (Page 55) How does deformation change
Earths surface?
  • It causes it to
  • Bend
  • Stretch
  • Break
  • Tilt
  • Fold
  • Slide

14
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

15
Faults
  • 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

16
Strike-Slip Faults
  • 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

17
Normal Faults
  • A type of fault where the hanging wall slides
    downward
  • Tension forces cause normal faults

18
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

19
Reverse Faults
  • A type of fault where the hanging wall slides up
  • Compression forces cause reverse faults

20
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21
Figure 5 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

22
Guide For Reading Why do faults form and where
do they occur?
  • Faults usually occur along plate boundaries,
    where the forces of plate motion compress, pull,
    or shear the crust so much that the crust breaks

23
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

24
What is friction?
  • A force that opposes the motion of one surface as
    it moves across another surface

25
Friction exists because
  • surfaces are not perfectly smooth.

26
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

27
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

28
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

29
The San Andreas fault in California is a
transform boundary that contains ___ stress.
  • high

30
Fault-Block Mountain
  • A mountain that forms where a normal fault
    uplifts a block of rock

31
How does the process of a fault-block mountain
begin?
  • 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

32
Folds
  • A bend in rock that forms where part of Earths
    crust is compressed

33
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

34
Anticline
  • Anticline An upward fold in rock formed by
    compression of Earths crust

35
An example of an anticline is the _________.
  • Black Hills of South Dakota

36
When and how did this location form?
  • Black Hills began to form about 65 million years
    ago

37
Syncline
  • Syncline A downward fold in rock formed by
    tension in Earths crust

38
An example of a syncline is the _____.
  • Illinois Basin

39
This syncline stretches _____ from the western
side of _____ through the state of _____.
  • 250 kilometers
  • Indiana
  • Illinois

40
Plateaus
  • A large area of flat land elevated high above sea
    level

41
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
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