THE EARTH’S
INTERIOR
Introduction
What to expect:
This module will help you
visualize and understand the
composition and structure of
the Earth’s interior.
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.

Seismic Waves
The energy that radiates in all directions from the focus of an earthquake.
Wave
Direction
Epicenter
Fault
Focus
Types of Seismic Wave
Surface waves

Body Waves

Surface Waves

can only travel through the surface of
the Earth
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.
Love Wave
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
Rayleigh Wave
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 Swave
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

Seismic Waves movement
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.
OUR HOME PLANET, EARTH

Our Earth is about average among the
planets in the Solar System, in many
respects:
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
 largest
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
OUR HOME PLANET, EARTH
The Composition of the Earth’s Interior
Seismic Waves: Interior Part
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
The Crust

thinnest and the outermost
layer of the Earth that extends
from the surface to about 32
kilometers below
 Continental
 Oceanic
Continental
Continental
Lithosphere
Oceanic
Moho
Root
Asthenosphere
Stanley, 1989, p. 14
Stanley, 1989, p. 14
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.
Elements in the Crust
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.
Layers
The Core
o
2000-5000 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
