This document provides an overview of the Earth's interior structure based on seismic wave evidence. It discusses how seismic waves like P-waves and S-waves travel through different layers, revealing details about the composition and state of those layers. The existence of an S-wave shadow zone indicated the inner core is solid, while P-wave refraction showed bending consistent with a liquid outer core. Later discoveries of an inner core within the outer liquid core helped establish the current model of a solid inner core within a liquid outer core surrounded by the mantle and crust.

1. NATIONAL
ACHIEVEMENT TEST
REVIEW IN EARTH
SCIENCE
(EARTH’S INTERIOR)
MYLENE ROMERO NEVIAR- Facilitator

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

3. PRE-ASSESSMENT
1. An S-wave shadow zone is formed as
seismic waves travel through the earth’s
body. Which of the following statements
does this S-wave shadow zone indicate?
A. The inner core is liquid
B. The inner core is solid
C. The mantle is solid
D. The outer core is liquid.

4. PRE-ASSESSMENT
2. Why are there no P-waves or S-waves
shadow ?
A. P-waves are absorbed and S-waves
are refracted by Earth’s outer core.
B. P-waves are refracted and S-waves
are absorbs by Earth’s outer core
C. Both the P-waves and S waves are
refracted by Earth’s outer core.
D. Both the P-waves and S waves are
absorbs by Earth’s outer core.

6. PRE-ASSESSMENT
3. What makes up the lithosphere?
A. Continental crust
B. Crust and the Upper mantle
C. Oceanic Crust and the upper mantle.
D. Upper mantle

7. PRE-ASSESSMENT
4. Miners dig into the Earth in search for
precious rocks and minerals. In which layer is
the deepest explorations made by miners?
A. Crust
B. Inner Core
C. Mantle
D. Outer Core

8. PRE-ASSESSMENT
5. How do you compare the densities of the
Earth’s crust, mantle and core?
A. The mantle is less dense than the core
but denser than the crust.
B. The mantle is less dense than both
core and the crust.
C. The mantle is denser than the core but
less dense than the crust
D. The mantle is denser than both the
core and the crust.

9. PRE-ASSESSMENT
6. The movement of the lithospheric plates is
facilitated by a soft, weak and plastic-like
layer. Which of the following layers is
described in the statement?
A. Asthenosphere
B. Atmosphere
C. Lithosphere
D. Mantle

10. PRE-ASSESSMENT
7. Alfred Wegener is a German scientist
who hypothesized that the earth was once
made up of a single large landmass called
Pangaea. Which of the following theories
did Wegener propose?
A. Continental Drift Theory
B. Continental Shift Theory
C. Plate Tectonics
D. Seafloor Spreading Theory

11. PRE-ASSESSMENT
8. If you are a cartographer, what will give you
an idea that the continents were once joined?
A. Ocean depth
B. Position of the South pole
C. Shape of the continent
D. Size of the Atlantic Ocean

12. PRE-ASSESSMENT
9. Which observation was NOT instrumental in
formulating the Hypothesis of seafloor
spreading?
A. Depth of the Ocean
B. Identifying the location of glacial
deposits
C. Magnetization of the Oceanic Crust
D. Thickness of Sea floor sediments

13. PRE-ASSESSMENT
10. As a new seafloor is formed at the mid-
ocean ridge, the old seafloor farthest from
the ridge is destroyed. Which of the stated
processes describes how the oceanic crust
plunges into the Earth and destroyed at the
mantle?
A. Convection
B. Construction
C. Diversion
D. Subduction

14. PRE-ASSESSMENT
11. In 1912, Alfred Wegener proposed a
theory that the earth is once a single
landmass. What is the name of the Mesozoic
supercontinent that consisted of all of the
present continent?
A. Eurasia
B. Laurasia
C. Pangaea
D. Gondwanaland

15. PRE-ASSESSMENT
12. Who were the two scientists who
proposed the theory of seafloor spreading in
the early 1960s?
A. Charles Darwin & James Hutton
B. Harry Hess & Robert Dietz
C. John Butler & Arthur Smite
D. F. Vine and D. Mathews

16. PRE-ASSESSMENT
13. If the Atlantic Ocean is widening at a rate
of 3 cm per year, How far (in Kilometers) will
it spread in a million years.
A. 3 kilometers
B. 30 kilometers
C. 300 kilometers
D. 3000 kilometers

17. PRE-ASSESSMENT
14. Which of the following increases with
distance from a mid-ocean ridge?
A. The age of oceanic lithosphere
B. The thickness of the lithosphere
C. The depth to the seafloor
D. All of the above

18. PRE-ASSESSMENT
15. If all the inner layers of the Earth are firm
solid, what could have happened to Pangaea
A. It remained as a supercontinent
B. It would have become as it is today
C. It would have slowly disappeared in the
ocean
D. It would have stretched and covered the
whole world.

19. What are seismic waves?
 These are the waves of energy
caused by the sudden breaking of
rock within the earth or an
explosion. They are the energy
that travels through the earth
and recorded on seismographs.
 Full of energy
 Very fast moving (Speed in km/s)
Breaking of
rocks
Earthquake Seismic
Waves

20. Types of Seismic Wave
Surface waves
Body Waves

21. `
Surface Waves(L-Waves)
Moves along the earth’s surface.
They move up and down. Love WavesRaleigh Waves

22. `
These waves are a type of surface acoustic
wave that travel on solids
Rayleigh Waves
Named for John William Strutt, Lord
Rayleigh, who mathematically predicted
the existence of this kind of wave in 1885.
Rolls along the ground just like a
wave rolls across a lake or an ocean.
Because it rolls, it moves the ground up
and down, and side-to-side in the same
direction that the wave is moving.
Most of the shaking felt from an
earthquake is due to the Rayleigh wave,
which can be much larger than the other
waves.

23. Rayleigh Wave

24. 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.

25. Love Wave

26. ` Surface Waves(L-Waves)
Land waves move along the surface of the earth and cause it to move
up and down like something bobbing on the surface of the ocean.

27. ` Surface Waves(L-Waves)
Land waves only move along the surface of the earth.
Their speeds vary depending on the material, rock or soil,
forming the surface. These waves cause the surface to
move up and down. These are the waves that cause
The to buildings and other structures
during an earthquake.

28. `
Body Waves
Primary
Waves
Secondary
Waves
push and pull side to side

29. 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

30. 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

31. 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

32. ` Primary Waves
Primary wavesare “compression waves”.
They push and pull the rocks of the earth's surface. They can move
through solid rock and fluids like water or the liquid core layers of the earth And
first to 'arrive' at a seismic station.

33. `
Primary waves push and pull on the rocks through which
they are traveling. This creates a back and forth movement
on the Earth's surface. This is just like sound waves pushing
and pulling the air. Have you ever heard a big clap of thunder
and heard the windows rattle at the same time? The windows rattle because the
sound waves were pushing and pulling on the window glass much like P-waves
push and pull on rock.
Primary Waves

34. ` Secondary Waves
Secondary waves travel slower than primary waves. Also called “shear waves
"or “Transverse Waves”.
They create a side to side motion in the rocks through which they are
traveling.

35. ` Secondary Waves
Unlike the other earthquake waves, S-waves cannot
travel through water or the liquid rock of the Earth's
core layer. They can Travel through solid only-waves will rock buildings side-
to-side.

36. 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

37. Seismic Waves movement

38. `
Seismic Waves

39. Types ofSeismicWaves

40. Cross section of the Earth as seismic waves travel
through it

41. 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

42. 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

43. 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

44. 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

45. 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

46. 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

47. 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

48. 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

49. 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.

50. The Composition of the Earth’s Interior

51. 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.

52. The Composition of the Earth’s Interior

55. DENSITY AND TEMPERATURE VARIATION IN DEPTH

57. The Crust

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

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

60. 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

61. 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.

62. 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.

63. 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.

64. Elements in the Crust

65. 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.

67. 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

68. 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

69. 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

70. 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.

71. Layers

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

74. 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

75. 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

76. 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

77. 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.

78. 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

79. 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.

80. The core is important as..
 It is thought to be the main reason behind the
driving forces of convective currents in Mantle.
 It is responsible to maintain Earth’s magnetic
field.

82. If the core stops spinning, the magnetic field will collapse resulting in
destruction of Earth’s surface by violent solar storms.