Title: Earth
1Earths Crust in Motion
- EQ How do stress forces affect rock?
2Earthquakes
- 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
4Stress
- Stress A force that acts on rock to change its
shape or volume
EQ How do stress forces affect rock?
5What 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?
7Shearing
- Shearing Stress that pushes a mass of a rock in
opposite, horizontal directions
EQ How do stress forces affect rock?
8Tension
- Tension Stress that stretches rocks so that it
becomes thinner in the middle
EQ How do stress forces affect rock?
9Compression
- Stress that squeezes rock until it folds or breaks
EQ How do stress forces affect rock?
10Figure 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?
11Deformation
- 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?
12Checkpoint (Page 55) How does deformation change
Earths surface?
- It causes it to
- Bend
- Stretch
- Break
- Tilt
- Fold
- Slide
13Guide 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
14Faults
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
15Strike-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
16Normal Faults
- A type of fault where the hanging wall slides
downward - Tension forces cause normal faults
EQ How do stress forces affect rock?
17Hanging 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?
18Reverse Faults
- A type of fault where the hanging wall slides up
- Compression forces cause reverse faults
EQ How do stress forces affect rock?
19Checkpoint (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
20Why 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
21EQ How do stress forces affect rock?
22Which 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?
23What 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?
24Describe 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?
25Describe 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?
26Describe 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?
27Fault-Block Mountain
EQ How do stress forces affect rock?
- A mountain that forms where a normal fault
uplifts a block of rock
28How 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
29Folds
EQ How do stress forces affect rock?
- A bend in rock that forms where part of Earths
crust is compressed
30How 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?
31Anticline
- Anticline An upward fold in rock formed by
compression of Earths crust
EQ How do stress forces affect rock?
32Syncline
EQ How do stress forces affect rock?
- Syncline A downward fold in rock formed by
tension in Earths crust
33Plateaus
- A large area of flat land elevated high above sea
level
EQ How do stress forces affect rock?
34Guide 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