Department of Education

National Capital Region

Schools Division of Parañaque City
Self – Learning Module
Science 8 Quarter 2 Week 1
Faults and Earthquakes

Learning Competencies (Essential Competencies):

A. Using models or illustrations, explain how movements along faults
generate earthquakes. (S8ES-IIa-14)

Objectives:
At the end of the activity, the students should be able to:
a. define fault and explain how it is formed.
b. describe the three types of fault and relate the types of stress associated with each
type.
c. describe the effects of bending of rocks along faults.
d. simulate how movements along faults generate earthquakes using models.
.
Brief Introduction
The planet Earth consists of three layers: the crust, the mantle, and the core. The
Earth’s lithosphere composed of the crust and the uppermost mantle is broken into many
pieces called tectonic plates that are in constant motion due to convection in the mantle. The
intense heat and pressure within the Earth cause molten magma to rise, cool, and eventually
sink. The movement of the tectonic plates provides the stress causing the rock surface to
break. A fault is a large crack formed in the Earth’s crust as a response to stress. Earthquakes
may happen near cracks resulting from a sudden release of energy that travels in the form of
waves. Movement along faults can be sideways or horizontal and vertical (up or down).
Earthquakes are also known as quake, tremor, or tremblor and classified as tectonic,
or volcanic. The earthquake caused by sudden movements along faults and plate boundaries
is known as a tectonic earthquake. The volcanic earthquakes are caused by rising hot molten
materials beneath active volcanoes.

1
 LET’S RECALL:

Directions: Rearrange the letters below to get the correct words being described by the clues.
1. The force applied to a rock, which may cause rock layers to break.

2. The process where molten magma rises and sinks due to temperature difference.

3. A large crack in the Earth’s surface where parts of the crust move relative to one
another.

4. The shaking of the ground caused by the release of energy from the movement of
plates creating waves.

5. The rigid pieces of Earth’s crust and upper part of the mantle. (2 WORDS)

LET’S UNDERSTAND

Stress is the force exerted on rocks, which can cause rock deformation.
The types of stress that cause rock layers to break are shear, tension, and compression.

Shear Tension Compression

Figure 1: Different Types of Stress

Photo Credit: Earth Science-Unit IV-Plate Tectonics-Study Guide,Copyright © 2017

Quipper Limited.

1. Compression stress squeezes or pushes rocks together causes a reverse fault. It is

the type of stress found at convergent plate boundaries in which two tectonic plates
are plowing into each other.

2
 2. Tension stress pulls rocks apart from each other creating normal faults. It is the most
common type of stress in divergent boundaries.
3. Shear stress is when forces act parallel to each other but in the opposite direction or
when rock slabs slide past each other horizontally. Shear stress produces transform
fault or strike-slip fault and is found at transform fault boundaries.

A fault is a break or fracture in the Earth’s crust in response to stress caused by the
movements of the tectonic plates. There are two parts of a fault: the fault line and the fault
blocks. The faultline is the trace of fracture or break on a rock surface. Fault blocks are either
hanging walls or footwall that interact during faulting of rock layers. Hanging wall (HW) is a
rock above the fault plane. Footwall is a rock below the fault plane.

Types of Faults

1. Normal fault -The hanging wall block drops downward relative to the footwall. It is
the product of tension and stress. Ex. Great Rift Valley in Africa.
2. Reverse or thrust faults - The hanging wall (upper block) moves upward relative to
the footwall (lower block). It is the result of compression stress. Ex. Himalaya
Mountains.
3. Strike-slip fault - Rocks move horizontally. Little or no vertical movement. It forms
from shear stress. Ex. San Andreas Fault in California

The constant motion of the tectonic plates continues to shape the Earth’s structure.
The forces that move the plates create stresses within the Earth’s crust and respond to stress
by flowing, bending, or breaking. As stress increases, the rocks suddenly snap or slip, creating
a release of energy in the form of waves that travel through the Earth’s crust and cause an
earthquake.

LET’S APPLY

Directions:
● Examine the images below and describe the fault type based on the stress
applied on the Earth’s crust, as indicated by the arrows in the illustration.
● Identify the symbol X and Y in the picture as a hanging wall or a footwall.

3
 1. 2.

Fault type: _______________ Fault type: _______________

Symbol X: ________________ Symbol X: _______________
Symbol Y: ________________ Symbol Y: _______________

3. 4.

Fault type: ___________________ Fault type: __________________

Photo Credit:
http://geotripperimages.com/Tectonic_Processes/Faults.htm
http://www.pitt.edu/~cejones/GeoImages/7Structures/ReverseFaults.html
https://en.wikipedia.org/wiki/Fault_(geology)
https://www.amusingplanet.com/2015/03/the-san-andreas-fault-of-california.html

LET’S ANALYZE
Discussion Questions: Place answer on your answer sheets.
1. How do plate movements generate faults? _________________________________
2. Explain what causes faults to move? ______________________________________
3. How are rocks affected by different types of stress? __________________________
4. Explain how movements along faults generate earthquakes? ___________________
5. Describe what happens to rock when it bends due to stress? ___________________
6. Explain how each type of fault changes the Earth’s surface? ___________________

4
 LET’S EVALUATE

A. Directions: Choose the letter of the best answer.

1. Which statement best describes a normal fault?
a. Fault blocks slide past each other.
b. Compression thrusts the fault into reverse.
c. The hanging wall moves upward relative to the footwall.
d. The hanging wall moves downward relative to the footwall.
2. Which type of fault forms from compression stress?
Normal
Reverse
Shear
Strike-
slip
3. Identify the type of fault shown in the illustration below?
Normal
Reverse
Shear
4. Strike-slip
How do faults generate earthquakes?
a. An earthquake occurs when faults snap and slip, resulting from a sudden release
of energy that travels in the form of waves.
b. Molten rock materials accumulate and go out along the fault producing earthquake.
c. Earthquakes are caused by the formation of volcanoes, due to the collision of
tectonic plates.
d. Molten rock materials cause the Earth’s crust to spread, producing faults.
5. Which of the three types of stress cause the rock layers to form faults?
a. shearing stress, normal stress, and tension stress
b. compression stress, normal stress, and tension stress
c. deformation stress, tension stress, and shearing stress
d. tension stress, compression stress, and shearing stress

B. Directions:
a. Name the symbol X and Y in the picture as a hanging wall or footwall.
b. Classify the rock layers as a normal fault or reverse fault.

5
 X Y X Y

Fault type: _______________ Fault type: ______________

Symbol X: _______________ Symbol X: ______________
Symbol Y: _______________ Symbol Y: ______________

LET’S CREATE:

Directions:
1. Construct a fault model using the materials below:
glue, folder, tracing paper or bond paper, any coloring materials, pencil, pair of
scissors, and fault model diagram.
2. Trace the fault model diagram using a tracing paper or bond paper.
3. Color the rock layers according to the coloring key.

4. Paste the fault model on a folder.

5. Cut out the diagram and fold each side down to form a fault model similar to the
illustration below:

6. Paste or glue the corners of the fault model together.

6
SIMULATION ACTIVITY
● Hold the fault blocks together and then push it on the opposite side.
● Hold it again and pull the fault blocks away from each other.
● Try to slide the fault blocks in the opposite direction.
Questions:
a. Describe what happens when you push the fault blocks toward each other?
b. How about when you pull the fault blocks away from each other?
c. What happened to the fault blocks when you slide these in opposite directions?
d. What do you think would be the result of these movements on the Earth's crust?

Scoring Key
(Fault Model Making)
SCORE
CRITERIA 4 3 2 1
Following All directions in Most of the Some of the None of the
directions the activity were directions in the directions in the directions in the
followed. activity were activity were activity were
followed. followed. followed.
Color All white spaces Some white Lots of white No colors were
were colored spaces were not spaces were not used in making
completely colored. colored. the model.
Neatness The fault model The fault model The fault model The fault model
is very neat. is neat. has stray marks. is messy.

7
FAULT BLOCK DIAGRAM