none

2. Gem and her classmates were
busy writing when suddenly they
felt dizzy. They stopped writing
and looking at each other. They
felt shaking of the earth. Gem
looked up and saw hanging
pictures and lanterns swinging
slowly. The
teacher said, “There’s an earthquake!” She told them to
keep calm. After a while, the shaking stopped.

3. ____1. Have you ever experienced an earthquake?
____2. Are you afraid when there is an earthquake?
____3. Do you know what to do when there is an
earthquake?
____4. Do you shout when you are experiencing
earthquake?
____5. Do you know where to go when there is an
earthquake?
Answer the following with YES or NO.

4. Let’s find out: “What are the layers of the Earth”
Let’s use these materials:
Picture of earth with its layers, model showing the
layers of the earth, clay, papier-mache and paint,
polystyrene foam ball, water color or water-based paint,
brush
Let’s do it this way:
1. Work by groups of three or four pupils.
2. Study the picture of layers of the Earth.
Activity: Making Models of the Earth

5. 3. Choose one of the following materials to make a
model of Earth’s interior
a. Clay of different color
b. Polystyrene foam ball and watercolor or water-
based paint
c. Paper-mache and paint.
4. Keep the depth and thickness of each layer of your
model using the scale below.
5. Label the different layers.

6. 6. Compare your model with the models of other
groups.
Let’s write our observations:
1. What are the layers of the Earth?
2. Which layer is the thinnest?
3. Which layer is the thickest?
4. Which layer is made up of molten materials?
5. Which layer is between the crust and the core?

7. Let’s share what we have learned:
1. Why can we not actually see the layers of Earth?
_______________________________________________
2. How do we know about the Earth’s interior?
_______________________________________________
What happens when there is an earthquake? Do the
following activity and see what happens when the
earth shakes.

8. Let’s find out: What happens during an earthquake?
Let’s use these materials:
Shoebox, rock or stones of different sizes enough to
fill half of the shoebox, string, soil, small toys
Let’s do it this way:
1. Make a small hole at one side of the shoebox.
2. Tie one big string around one big piece of rock or
stone.
Activity: Simulating an Earthquake

9. 3. Arrange the rocks or stones in the shoebox. Put the
stone with a string at the middle. Insert the tip of the
string to the small hole.
4. Cover the rocks with soil up to the tip of the
shoebox. Make the soil on top compact by pressing
it.
5. Set some small toys on top of the soil.
6. Pull the string suddenly (not so strong). Observe the
soil and the toys.

10. 7. Give the string four strong and sudden tugs. Observe
what happens to the soil and toys.
Let’s state our observations:
1. What happens to the soil and toys on your first pull?
2. What happens to the soil and toys when you gave
four strong and sudden tugs to the string?
3. If you compare your activity with a real earthquake,
where does earthquake originate?

11. Let’s share our knowledge:
What happens during an earthquake?
____________________________________________________________
____________________________________________________________
______________________________

12. Earth’s Interior Geologist call the solid
part of Earth’s surface as
lithosphere. It is made of solid
rock materials that originated
from its interior. According to
them, Earth’s interior is divided
into three layers: the crust,
mantle and core.

13. The crust is the
outermost and the
thinnest layer of Earth
ranging from 5 to 100 km
thick. It is the upper part
of the lithosphere. It is
where the people and
other living things live. It
is divided into continental
crust and oceanic crust.
The Crust

14. The crust beneath the
continents that has an
average thickness of
about 32 km is called
continental crust.
It is thickest beneath the
mountains, which can be
greater than 70km thick.
Elements like potassium,
The Crust

15. sodium, aluminum, and silicon are mostly found in this
part. Its composition is similar to granite rocks. The
crust beneath the oceans is called the oceanic crust. Its
average thickness is only about 8km thick. It is rich in
iron, silicon and magnesium. It is mostly made of basalt
rocks.

16. The mantle is the layer of
Earth between the crust and
the core. It extends to a depth
of about 2,900 km. It is the
largest layer of Earth that
covers about 67% of Earth’s
mass. It is made of thick liquid
containing the elements of
silicon, oxygen, iron and
The Mantle

17. In 1909, a Yugoslav
scientist named Andrija
Mohorovicic discovered a
boundary between the
crust and the mantle
through observation of
seismic waves that moved through the Earth. This special
boundary is called the Mohorovicic discontinuity or
simply called Moho.

18. The mantle is made up of
three layers: the uppermost layer,
which is the lower part of the
lithosphere, the asthenosphere,
and the lowermost part or lower
mantle. “Asthenosphere” is
derived from the Greek word
which means “weak layer.” This
layer of the mantle believed by
scientist to be

19. made up of mushy plastic-like rocks
with molten rocks. This soft, liquid
quality of the asthenosphere is the
reason why the plates of the
lithosphere above it, shift and slide
each other, creating the different
tectonic activity. Scientists also
believed that it is from this layer
that the hot molten magma rises
from the volcanic vents.

20. The core extends from the
bottom of the mantle to the
center of the Earth. It is
divided into the outer core
and the inner core. It
comprises 33% of Earth’s
mass. The outer core is made
up of hot molten materials
that contain iron and nickel.
The Core

21. The inner core is the
innermost layer of Earth. It is also
made up of iron and nickel. The
great pressure in the inner core
pushes the particles of iron and
nickel so tightly together that
the elements remain solid. The
presence of solid iron in the
inner core may explain the
existence of Earth’s magnetic
field.
The Core

22. A lot of evidence prove that
Earth’s interior is hot. The
geothermal energy, hot springs and
the hot molten rocks coming out
from an erupting volcano are proofs
that Earth’s interior is hot. The
decaying of radio-active elements
like uranium melts the rocks in the
mantle.
The Earth’s Interior is
Hot

23. Earth’s surface continually
changes over time. There are high
elevations and low lands. There are
shallow shores and deep trenches
in the ocean. These landforms can
change over time. Some lowlands
may become higher and some
highlands may turn to lowlands.
Changes on the Earth’s Surface

24. Such changes that occur on the crust are caused by forces
within Earth itself. The rock layers become deformed due to
stress, high temperature, and great pressure within Earth’s
interior.
The entire crust consist of 10 major tectonic plates that
are continuously moving. These tectonic plates push, pull
and collide against each other at a boundary or plate
edges. During these process, stress such as tension,
compression and shearing build up at the plate edges that
make the rocks bend, break or twist which results to the
occurrence of earthquake.

25. Earthquakes happen almost everywhere. Such
occurrences are studied in the field of science called
seismology. The groups of scientist who study earthquakes
are called seismologists. They monitor earthquakes,
determine how strong an earthquake is, and describe the
location and seismic waves of earthquakes. However, they
cannot predict when and where earthquakes occur.
Earthquakes

26. An earthquake is shaking or
trembling of Earth’s crust that
result from the faulting of rocks
and erupting of volcanoes.
Earthquakes that result from the
faulting of rocks are called
tectonic earthquakes while those that result from erupting
volcanoes are called volcanic earthquakes. During faulting,
stress builds up along the tectonic plate edges creating
some faults.

28. When rocks are stretched or bent, they store energy and if
they are deformed beyond their limit, they break and the
stored energy is released. The energy released is in the form
of vibrations. These vibrations in Earth’s crust are called
earthquakes.
Earthquakes differ in strength and in depth at which
they begin. Scientists estimate that one earthquake occurs
every 30 seconds and more than one million earthquakes
occur every year. The vast majority of earthquakes are so
small that the surface of Earth barely moves.

29. Scientists use scales
to describe the strength
of an earthquake. They
refer to intensity when
they measure the effects
of an earthquake in a
particular place. They do
not use any instrument to
measure intensity. They
observe,

30. record, and compare the effects of the damages of the
earthquake. The intensity of an earthquake depends on
the distance of a certain place from the epicenter since
the shaking of the Earth’s surface lessens as it goes
farther from the epicenter. The first intensity scale used
by the seismologists is the Mercalli Scale developed by
Giuseppe Mercalli in 1992. The Philippine Institute of
Volcanology and Seismology (PHIVOLCS) uses the
PHIVOLCS

31. Earthquake Intensity Scale. This scale is based on the
Rossi-Forel Scale, one of the first seismic scales to reflect
earthquake intensities. This scale was developed by
Michele Stefano Conte de Rossi of Italy and Francois-
Alphonse Forel of Switzerland in the late 19th century.

32. Study the table.
Intensity Details Description
I Scarcely
Perceptible
Perceptible to people under favorable
circumstances. Delicately balanced
objects are disturbed slightly. Still water
in containers oscillates slowly.
II Slightly Felt Felt by few individuals at rest indoors.
Hanging objects swing slightly. Still
water in containers oscillates noticeably.

33. Intensity Details Description
III Weak Felt by many people indoors especially
in upper floors or buildings. Dizziness
and nausea are experienced by some
people. Hanging objects swing
moderately.
IV Moderately
Strong
Felt generally by people indoors and by
some people outdoors. Light sleepers
are awakened. Vibration is felt like the
passing of a heavy truck.

34. Intensity Details Description
V Strong Generally felt by most people indoors
and outdoors. Many sleeping people
are awakened. Strong shaking and
rocking felt throughout buildings.
Hanging objects swing violently.
Standing vehicles rock noticeably.
VI Very Strong Some people lose their balance.
Motorists feel like they are driving with
flat tires. Heavy objects and furniture
move or may be shifted

35. Intensity Details Description
Very old or poorly built houses and
man-made structures are slightly
damaged.
VII Destructiv
e
People find it difficult to stand in upper
floors. Heavy objects or furniture
overturn or topple. Some well-built
structures are slightly damaged. Some
cracks may appear on dikes, fish ponds,
road surfaces or concrete walls. Trees
are shaken strongly.

36. Intensity Details Description
VIII Very
Destructive
People find it difficult to stand even
outdoors. Many well-built buildings are
considerably damaged. Concrete dikes
and foundations of bridges are
destroyed by ground settling or
toppling. Railway tracks are bent or
broken. Fissures and fault ruptures may
be observed.
IX Devastati
ng
People are forcibly thrown to the
ground. Most buildings are totally
damaged. Bridges and elevated

37. Intensity Details Description
concretes are toppled or destroyed.
X Completel
y
Devastati
ng
Practically all man-made structures are
destroyed. Massive landslides and
liquefaction, subsidence and uplifting of
landforms and many ground fissures are
observed.

38. Several devastating earthquakes
already occurred around the world
especially in the areas along the
Pacific Ring of Fire. The Pacific
Ring of Fire is a circle belt along
the Pacific Ocean where the plate
boundaries are and where a lot of
earthquakes occur. It is also in
these places where there are a lot
of active volcanoes.

39. What are the effects of earthquakes?

40. On July 16, 1990, Luzon was rocked
with a devastating magnitude 7.8
earthquake. It brought so much
damaged such as the toppled Hyatt
Hotel in Baguio City and the rumbled
school building in Cabanatuan, and
caused the death of a lot of people
including school children. Landslides
also occurred because of the strong
earthquake.

41. On March 11, 2011,
Sendai City, Japan
suffered terrifying 10
meter high tsunami
caused by a magnitude
8.9 earthquake. It is also
caused fire and
destruction of the nuclear
reactors of Fukushima
Nuclear Plant.

42. What is magnitude?
The measure of energy
released by an earthquake is
referred to as magnitude.
Scientists measure the
magnitude of an earthquake
using the instrument called
seismograph. Seismograph
records the shaking of the
ground as wavy lines on paper.

43. Modified Richter Scale
Magnitude Estimated Effects
2.0 Can be detected only by seismograph
3.0 Can be felt at the epicenter
4.0 Felt by most in the area
5.0 Causes damage at the epicenter
6.0 Causes widespread damage
7.0 Causes great, widespread damage

44. A. Read each test item carefully. Write the letter of the
correct answer.
1. The shaking of Earth’s crust is called __________.
a. Earthquake c. erosion
b. Tsunami d. landslide
2. What is the innermost layer of Earth’s interior?
a. crust c. Moho
b. mantle d. core

45. 3. When scientists observe the effects of earthquakes,
they refer to _______.
a. Epicenter c. magnitude
b. Intensity d. surface waves
4. What is the instrument that measures the magnitude
of an earthquake?
a. Seismogram c. barograph
b. Seismograph d. scale

46. 5. What do scientists use to describe the strength of the
earthquake?
a. Scales c. diagrams
b. Charts d. graphs
6. What was the first intensity scale used by the
scientists?
a. Mercalli Scale c. Modified Richter Scale
b. Richter Scale d. PHIVOLCS Intensity Scale

47. 7. Which of the following are effects of earthquakes?
I. Loss of lives III. Fire
II. Destruction of properties IV. Tsunamis
a. I,II,III c. I,III,IV
b. I, II, IV d. I, II, III, IV
8. Which best describes tsunamis?
a. Seismic waves along the seashore.
b. Giant ocean waves caused by earthquakes
c. Giant ocean waves beneath the faults
d. Giant seismic waves on Earth’s crust

48. 9. Earthquake causes changes on Earth’s surface. Which
of the following are observed in the environment
after an earthquake?
I. Landslide III. Dried land
II. Fissures on the groundIV. Fallen trees
a. I only c. I, II, III
b. I and II d. II, III, IV

49. a. Higher magnitude earthquakes cause widespread
damage.
b. Higher magnitude earthquakes cause lesser
damage.
c. Higher magnitude earthquakes can be felt by only a
few.
d. Higher magnitude earthquakes have slow seismic
waves.
10. Which of the following is true about the magnitude of
earthquakes?

50. Answer the following questions.
1. How do you feel when you hear about
earthquakes?
2. What are the effects of strong earthquakes?
3. How can you help the victims of earthquakes?
4. Differentiate intensity from magnitude.
5. Which intensity scales are destructive according to
the PHIVOLCS Intensity Scale? Describe the details
of destruction.