The Earth's Interior

THE EARTH’S
INTERIOR
Introduction

 In Module 1, you have learned about
the different processes and landforms
along plate boundaries that slowly
shaped the Earth’s surface.
 In Module 2, you will learn the
connection between these processes
with the internal structure and
mechanisms of our planet.

What to expect:
This module will help you
visualize and understand the
composition and structure of
the Earth’s interior.

It provides you scientific
knowledge that will help you
describe the different layers
of the Earth as well as
understand their
characteristics.

 You will also learn concepts that
explain the physical changes that it
underwent in the past.
 This module also consists of activities
that will help you develop your critical
thinking skills to have a deeper
understanding about the planet where
you live.

Key Questions:
1. How do the structure and composition of the
Earth cause geologic activities and physical
changes?
2. What are the possible causes of the
lithospheric plate movements?
3. What proves the movement of the tectonic
plates?

Studying the Earth’s Interior
 Scientists tried to explore and
study the interior of the Earth.
Yet, until today, there are no
mechanical probes or actual
explorations done to totally
discover the deepest region of
the Earth.

How did they know?
 The Earth is made up of three layers:
the crust, the mantle, and the core.
 The study of these layers is mostly
done in the Earth’s crust since
mechanical probes are impossible
due to the tremendous heat and very
high pressure underneath the Earth’s
surface.

Reading Resources and
Instructional Activities
Read the given
resources and answer
Act. 1.

Activity 1A: Amazing Waves!
Objectives:
 Define seismic waves scientifically.
 Differentiate the different types of
seismic waves.
 Recognize the importance of
seismic waves in the study of the
Earth’s interior.

Procedure: (1whole)
 Construct your own organizer
that shows necessary information
and summarizes the concept
about seismic waves.
 Answer Q1 and Q2.

Seismic Waves
 Seismic waves from earthquakes are used to
analyze the composition and internal structure
of the Earth.
What are seismic
waves?

Seismic waves
 Earthquake is a vibration of the
Earth produced by the rapid
release of energy.
 This energy radiates in all
directions from the focus in the
form of waves called seismic
waves.

Earthquake: Seismic Wave
Wave
Direction
Fault
Epicenter
Focus

Types of Seismic Wave
Surface waves
Body Waves

Surface Waves
 can only travel through the surface of
the Earth
 arrive after the main P and S waves
2 Types of Surface Waves
 Love Waves
 Rayleigh Waves

Love Wave
 named after A.E.H. Love, a British
mathematician who worked out the
mathematical model for this kind of wave in
1911.
 faster than Rayleigh wave
 it moves the ground in a side-to-side
horizontal motion, like that of a snake’s
causing the ground to twist
 cause the most damage to structures during
an earthquake.

Rayleigh Wave
 named after John William Strutt, Lord
Rayleigh, who mathematically predicted the
existence of this kind of wave in 1885
 wave rolls along the ground just like a wave
rolls across a lake or an ocean
 up and down or side-to-side similar to the
direction of the wave’s movement
 shaking felt from an earthquake

Body waves
can travel through the Earth’s
inner layers
they are used by scientists to
study the Earth’s interior
higher frequency than the
surface waves

Body waves
2 types
P-Waves (Primary waves)
S-waves (Secondary waves)

P-waves (Primary)
is a pulse energy that
travels quickly through the
Earth and through liquids
travels faster than the S-
wave
it reaches a detector first

P-waves (Primary)
 compressional waves, travel by
particles vibrating parallel to the
direction the wave travel
 move backward and forward as they
are compressed and expanded
 they travel through solids, liquids
and gases

S-waves (Secondary/Shear)
 pulse energy that travels slower than
a P-wave through Earth and solids
 Move as shear or transverse waves,
and force the ground to sway from
side to side, in rolling motion that
shakes the ground back and forth
perpendicular to the direction of the
waves

S-waves (Secondary/Shear)
cannot travel through any
liquid medium led
seismologists to conclude
that the outer core is liquid

Cross section of the Earth as seismic waves travel
through it

Propagation of Seismic Waves
Through Earth’s Interior
Longitudinal waves travel through both
solids and liquids.
Transverse waves travel through
solids only.

Remember:
 P-waves are detected on the other side
of the Earth opposite the focus.
 A shadow zone from 103° to 142°
exists from P-waves
 Since P-waves are detected until 103°,
disappear from 103° to 142°, then
reappear again, something inside the
Earth must be bending the P-waves

Remember:
 existence of a shadow zone, according
to German seismologist Beno
Gutenberg (ɡuː t ən bɛʁk), could only be
explained if the Earth contained a core
composed of a material different from
that of the mantle causing the bending of
the P-waves
 To honor him, mantle–core boundary is
called Gutenberg discontinuity

Remember:
 From the epicenter, S-waves are detected
until 103°, from that point, S- waves are no
longer detected
 S-waves do not travel all throughout the
Earth’s body
 knowing the properties and characteristics of
S-waves (that it cannot travel through liquids),
and with the idea that P-waves are bent to
some degree, this portion must be made of
liquid, thus the outer core

Remember:
 1936, the innermost layer of the Earth was
predicted by Inge Lehmann, a Danish
seismologist
 discovered a new region of seismic reflection
within the core
 Earth has a core within a core

Remember:
 the outer part of the core is liquid based from the
production of an S wave shadow and the inner
part must be solid with a different density than
the rest of the surrounding material
 size of the inner core was accurately calculated
through nuclear underground tests conducted in
Nevada.
 echoes from seismic waves provided accurate
data in determining its size

Bring the ff. (by grp)
15g cornstarch
2 small cups
Medicine dropper
Stirring rod or spoon

Act. 1B. Simulating Plasticity
Procedure:
 Put 15 g cornstarch into one of the
beakers. Put 10 ml water into the other
beaker.
 Add one drop full of water to the
cornstarch. Stir the mixture.
 How does the mixture react like; solid,
liquid or gas?

 Continue to add water to the mixture,
one drop full at a time. Stir the
mixture after each addition.
 Stop adding water when the mixture
becomes difficult to stir.
 Pour the mixture into your hand.
 Roll the mixture into a ball and press
it.

Answer the ff. questions
 How does the mixture behave like?
 How is the mixture of cornstarch and
water similar to the earth’s mantle?
 How is it different from the earth’s
mantle?
 How does the plasticity of the earth’s
mantle influence the movement of the
lithospheric plates?

Bring the ff: (by grp)
hardboiled egg/s
 bread knife
used paper/newspaper
to work on

Activity 1C: Hard Boiled Earth
PROCEDURE:
1. Prepare the materials. (hardboiled
egg, bread knife, used paper to work
on)
2. Place used paper or newspaper on
your working area. Cut the egg into
halves using a knife or a cutter.

Procedure:
 Using qualitative observation, describe the
parts of the egg from the outermost to the
innermost by completing the table. Write your
answer on a piece of paper/ short bond paper.
PARTS OF THE EGG DECSRIPTION
EQUIVALENT TO
THE EARTH’S
LAYER
DESCRIPTION

Procedure:
4. Draw the appearance of the cut hard-boiled egg.
5. Answer the ff.
A. How many layers does a hard-boiled egg have?
B. Which is the largest part? The thinnest?
C. Compare the parts of the egg to the model of the
earth.
D. Aside from the hard-boiled egg, what other things
can you compare to the earth’s interior layers?

OUR HOME PLANET, EARTH
 Our Earth is about average among the
planets in the Solar System, in many
respects:
 largest and most massive of the four terrestrial planets,
but smaller and less massive than the four giant, or
Jovian, planets
 third in distance from the Sun among the four terrestrial
planets
 has a moderately dense atmosphere; 90 times less
dense than that of Venus but 100 times denser than that of
Mars

OUR HOME PLANET, EARTH
 Earth is also unique in many respects:
 the only planet with liquid water on its
surface.
 the only one having a significant (21%)
proportion of molecular oxygen
 to our best current knowledge, the only
planet in the solar system having living
organisms
 the only terrestrial planet having a
moderately strong magnetic field
 the only terrestrial planet having a large
satellite

The Solid Earth
 geology -the study of the structure, history,
and activity of the solid Earth, including its
interactions with the atmosphere,
hydrosphere, cryosphere, and biosphere
 solid Earth contains four major zones: the
core (which is divided into inner and outer
zones), the (upper and lower) mantle, the
asthenosphere, and the lithosphere

The Solid Earth
 the outer zones is not uniform and fixed
over the surface of the Earth, but shows
much variability with position and time.
 The field of plate tectonics deals with this
spatial and temporal variability.
 Geological phenomena such as
earthquakes, volcanoes, and continental
drift are accounted for by plate tectonics.

The Composition of the Earth’s Interior

HW 4:
 Describe the unique characteristics of
each interior layer of the earth. (10pts)
 Bring: (by group)
Coloring materials
Pencil
Marker

Activity 2: Our Dynamic Earth
Objectives:
Describe the properties of
the layers of the Earth.
Tell the composition of the
layers of the Earth.

Did you know?
 The deepest mine in the world, the
gold mine in South Africa, reaches a
depth of 3.8km.
But...
You would have to travel more than
1,600 times that distance-over
6000km-to reach the earth’s center.

DENSITY AND TEMPERATURE VARIATION IN DEPTH

The Crust
thinnest and the outermost
layer of the Earth that extends
from the surface to about 32
kilometers below
Continental
Oceanic

Stanley, 1989, p. 14
Continental
Stanley, 1989, p. 14
Continental
Root
Moho
Oceanic
Lithosphere
Asthenosphere

Continental
 mainly made up of silicon, oxygen,
aluminum, calcium, sodium, and
potassium
 mostly 35-40 kilometers
 found under land masses
 made of less dense rocks such as
granite

Oceanic
 oceanic crust is around 7-10
kilometers thick which its average
thickness is 8 kilometers.
 found under the ocean floor
 made of dense rocks such as basalt
 heavier than the continental crust.

The Crust: Continental
• GRANITE -crystalline
igneous rock
composed primarily of
quartz and feldspar.
• forms from slowly
cooling magma that
is subjected to
extreme pressures
deep beneath the
earth's.

The Crust: Oceanic
• BASALT -volcanic rock
• forms from lava flows along
mid-ocean ridges and also in
igneous intrusions such as
dikes and sills.
• Columnar jointing, pictured
here at Devil's Tower,
Wyoming, occurs when
molten basalt cracks as it
cools, producing separate,
polygonal fractures on the
surface of the rock.

Moho Discontinuity
 While studying the speed of
earthquake waves, Croatian
geophysicist Andrija Mohorovičić
discovers a boundary between
Earth's crust and mantle, which
becomes known as the Mohorovičić,
or Moho, Discontinuity.

The Mantle
 Beneath the crust is the mantle
 extends to about 2900 kilometers from the
Earth’s surface
 about 80% of the Earth’s total volume
 about 68% of its total mass
 mainly made up of silicate rocks
 and contrary to common belief, is solid, since
both S-waves and P-waves pass through it

The Mantle
 mostly made of the elements silicon, oxygen,
iron and magnesium
 lower part of the mantle consists of more iron
than the upper part
 lower mantle is denser than the upper portion
 temperature and the pressure increase with
depth
 high temperature and pressure in the mantle
allows the solid rock to flow slowly

Remember:
 The ability of the asthenosphere to
flow slowly is termed as plasticity.
 crust and the uppermost part of
the mantle form a relatively cool,
outermost rigid shell called
lithosphere (Gk.lithos means
“stone”) and is about 50 to 100
kilometers thick

Remember:
 Beneath the lithosphere lies the soft, weak layer
known as the asthenosphere (Gk. asthenes
means “weak”) made of hot molten material,
about 300 – 800o C
 upper 150 kilometers has a temperature enough
to facilitate a small amount of melting, and make it
capable to flow
 facilitates the movement of the lithospheric plates
 lithosphere, with the continents on top of it, is
being carried by the flowing asthenosphere.

The Core
2000-5000o C
core is subdivided into
two layers:
the inner
the outer core.

Outer Core
 2900 kilometers below the Earth’s
surface
 2250 kilometers thick
 made up of iron and nickel
 temperature reaches up to 2000oC at
this very high temperature, iron and
nickel melt

Outer Core
 Aside from seismic data analysis,
the Earth’s magnetic field
strengthens the idea that the
Earth’s outer core is molten/liquid
 mainly made up of iron and nickel
moving around the solid inner
core, creating Earth’s magnetism

The Inner Core
 made up of solid iron and nickel and has a
radius of 1300 kilometers
 about 5000oC
 extreme temperature could have molten the
iron and nickel but it is believed to have
solidified as a result of pressure freezing,
which is common to liquids subjected under
tremendous pressure

The Inner Core
 Aside from the fact that the Earth has a
magnetic field and that it must be iron or
other materials which are magnetic in nature,
the inner core must have a density that is
about 14 times that of water.
 Average crustal rocks with densities 2.8
times that of water could not have the
density calculated for the core.
 So iron, which is three times denser than
crustal rocks, meets the required density.

Clues that the inner core and the outer core
are made up of iron
 Iron and nickel are both dense and
magnetic.
 overall density of the earth is much
higher than the density of the
rocks in the crust
 suggests that the inside must be
made up of something denser than
rocks

Clues that the inner core and the outer
core are made up of iron
 Meteorite analysis have revealed that the
most common type is chondrite.
 Chondrite contains iron, silicon,
magnesium and oxygen; some contains
nickel.
 The whole earth and the meteorite roughly
have the same density, thus the Earth’s
mantle rock and a meteorite minus its iron,
have the same density.

HW5
 Write a short story that describes the
most exciting part of your own
imaginary journey to Earth’s center.
 Bring the ff. (by group)
scissors
old magazines
brown envelope

The Earth's Interior

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