O N level Plate Tectonics

1. Chapter 1: Living with Tectonic
Hazards
Part 1: Hazards of the world
Copy when you see the star

2. What is a Natural Hazard
•Earthquakes
•Volcano eruption
•Tsunami

3. Earthquake
• Is it possible for Singapore to experience an
earthquake?
• When tremors occur near fault lines, energy is
moved along the crust in waves.
• Such energy when sufficiently strong will
travel long distances.
• Over distance, the energy will reduce.
• If there is a massive earthquake in Indonesia,
we will feel it in Singapore.

4. What the Japanese are trained to do.
• Take a look at the next video.
• Pay attention to the specific action that the
Japanese people do in the event of an
earthquake in the following locations.
– Home
– When driving
– At the shops
• You will have to answer the worksheet after
watching the video so pay attention.

5. Let’s now attempt the exercise
• You have 10 minutes to
answer the questions on the
handout.
• Good luck!

6. What is the structure of the Earth?
•Core
•Mantle
•Crust Read up on Pg 7
in your textbook

7. Tectonic Plate
• The crust of the earth.
• Two general types
–Continental plate
• Less Dense, heavier
–Oceanic plate
• Denser, lighter

8. Continental Drift
• Theory that crustal plates are constantly
moving
• Convectional currents move in the mantle due
to the variations of temperature.
• Warmer magma near the core rises, pushing
the crust above to the sides before sinking
down upon losing the temperature.

9. Continental Drift Diagram

10. Evidence of Continental Drift Theory
• The changing shape of earth’s land
mass over earth’s history shows that
the plates are moving.
• The current location of the
continents on earth will continue to
change.

11. Continental Drift Diagram

12. SRP Work
• Watch the following video on Colliding
Continents
• Answer the questions in the SRP handout /
complete the groupwork
• http://www.youtube.com/watch?v=KCSJNBM
OjJs
• 50 mins National Geographic video

13. Types of plate boundaries
• Convergent plate boundary
• Divergent plate boundary
• Transform plate boundary
• Refer to pg 9 textbook

15. Divergent plates
Oceanic – Oceanic divergence
• Area where two oceanic plates move
away from each other
• Magma moves up to the surface and
cools to form new oceanic crust
• Mid-Atlantic Ridge
• Possible to find underwater
volcanoes at such locations.

16. Diagram of Divergent plate boundary
(insert water surface for oceanic)

17. Continental – Continental divergence
• Area where two continental plates move away
from each other
• Magma moves up to the surface and cools,
forming new land.
• Often fractures form at the plate boundary,
forming a linear depression (rift valley)
• Great African Rift Valley

18. Exercise Time
• What do you think is needed to answer this
question?
– “ With the aid of diagram (s), explain the different
types of divergent plate boundaries that you have
learnt. Give specific examples.”
– Use Foolscap paper, complete your diagrams and
short explanations with examples.
– Diagrams in pencil please.

19. Part 2: Convergent plates

20. Plate movements
• If there are plate boundaries that are
diverging, at the end of that plate, there
will be convergence.
• 3 common types of convergent
boundaries
–Oceanic vs Oceanic plate
–Oceanic vs Continental plate
–Continental vs Continental plate

21. Reasons for convergence
• Plates converge due to continental drift.
• As the plates are pushed apart, they crash into
one another.
• Generally, the denser plate will subduct (sink)
below the less dense plate.
• The plate that is riding above will buckle (fold)
and massive landforms will occur.

22. Oceanic Crusts
• Beneath deep oceans
• Between 5km and 8km
• Consists of basalt
• Very dense and heavy
• Made of young rock (200 million years ago)

23. Continental Crust
• Beneath the earth’s land masses
• Between 30-60 km
• Consists of lighter rock, like granite
• Wide range of rock ages, from recent to over 4
billion year old.

24. Oceanic-oceanic plate boundaries
• When two oceanic plates converge
• Denser plate subducts under the less dense
plate
• Area where it subducts is called the
subduction zone
• A depression in the sea floor occurs at the
subduction zone and is called a deep sea
trench. (The Mariana Trench)
• Volcanic islands can also be formed at such
boundaries

25. Oceanic-oceanic plate boundaries

26. Oceanic-Continental plate convergence
• When an oceanic plate converges with a
continental plate.
• The dense oceanic plate is forced down into
the mantle.
• A deep sea trench is often formed at the
subduction zone. (Japanese deep sea trench)
• The continental plate folds and forms fold
mountains and volcanoes
• The Japanese Islands were a result of such
convergence.

27. Oceanic-Continental plate
convergence

28. Continental-Continental plate convergence
• When two equally dense continental plates
converge.
• There will still be a subduction occurring for
one of the plates. However there is a large
amount of friction built-up before it occurs.
• The strong force generated also causes
folding.
• At such plate boundaries, large mountain
ranges tend to form. (Himalaya)

29. Continental –continental plate
convergence

30. Transform boundary
• Occurs when plates slide past one
another horizontally.
• Huge energy released when friction is
overcome
• Large massive earthquakes experienced
• San Andreas Fault (California)

33. Exercise time
• Take a look at the handout (exercise 2).
• Using the information you have learnt so far,
answer the question to the best of your
abilities.
• Good luck

34. Review Comparison Table
Plate boundary type Associated landforms Example
Divergent
Oceanic-Oceanic Deep sea ridge Mid-Atlantic Ridge
Divergent
Continental-Continental Rift Valley Great African Rift Valley
Convergent
Oceanic-Oceanic Deep Sea Trench, Volcanoes,
Volcanic Islands
Mariana Trench, Mariana
Islands, Pacific plate and the
Philippine plate
Convergent
Oceanic-Continental Deep Sea Trench, subduction
zone, Volcanoes, Fold
mountains
Sunda Trench, Barisan
mountains, Australian plate and
the Eurasian plate
Convergent
Continental-Continental Deep sea trench, subduction
zone, fold mountains
Himalayas, Eurasian plate and
the Indian plate

35. Part 3
Landforms commonly associated at
tectonic boundaries

36. Fold Mountains

37. Fold Mountains
• The rock layers on the crust are
constantly exposed to pressure
• When they are compressed, they
fold, forming fold mountains.
• To upfold is called the anticline and
downfold is called the syncline.

38. Fold Mountains
• The major ranges are along
convergent plate boundaries
• The rocky mountains
• Himalayas
• Swiss Alps
• Pg 22

39. Rift Valleys /
Grabens

40. Rift Valleys
• Near divergent plate boundaries, plates pull
apart, causing land displacement.
• The downward displacement forms rift
valleys.
• Found commonly along divergent boundaries
• Also called Graben
• East African Rift Valley

41. Rift Valley diagram

42. Block Mountains / Horst
Yosemite National Park

43. Block Mountains
• When sections of the crust are pulled
apart by tensional force, some parts are
ripped off.
• The downward displaced areas are the
rift valleys
• The blocks left behind form block
mountains with steep sides.
• Also called Horst

44. Block Mountain diagram

45. Volcanoes

46. Volcanoes
• Landform formed by magma ejected from the
mantle.
• Magma builds up in the earth’s crust to form a
magma chamber.
• With repeated layering of ejected magma, the
volcano grows in height
• Found a divergent and convergent plate
boundaries where there is subduction.

47. • Vents are openings in the earth’s surface
with a pipe leading into the magma
chamber
• When magma is ejected onto the
surface, it is called lava. There is no
change in composition.
• Vulcanicity refers to the upward
movement of magma in the crust and
onto the surface.

49. Let’s take a short Brain Break
• Take a look at the
video on Mt St
Helens in America
• Half the volcano
was blown off in the
eruption

50. Viscosity
• The stickiness of the lava
• The resistance of the lava to flowing
• High viscosity flows slowly
• Low viscosity flows quickly
• Viscosity of the lava determines the
volcano’s shape

51. 2 Key types of Volcanoes
1.Shield Volcanoes
2.Composite Volcanoes
(Stratovolcanoes)

52. Shield Volcanoes

53. Shield Volcanoes
• Gentle sloping sides and a broad
summit
• Low-silica lava (low viscosity) present
• Lava flow is fast, spreading out
quickly
• Subsequent layering leads to wide
base with low overall height.
• Mount Washington in America

54. Stratovolcanoes

55. Stratovolcano
• Developed from successive eruptions.
• Ash and lava (coarse fragment) accumulate over
time.
• Layers of ash are locked in by subsequent layers of
lava.
• Tall volcanoes with concave bases formed.
• Secondary cones may develop as magma from the
vent seeps into the sides of the cone and erupts.
• Pyroclastic flow common
– Hot rock fragments and superheated gases.
• Mount Pinatubo, Philippines

56. Mt Pinatubo

57. Distribution of volcanoes
• Pacific Ring of Fire is the most active volcanic
activity occurs
• Many earthquakes and volcanic eruptions
occur along the ring of fire
• Ring is along several converging plates (Pacific,
Nazca, Philippines, Australian and Eurasian
plates)
• Volcanoes can also form where plates diverge.
• Pg 29

58. Pacific Ring of Fire

59. Volcanic Eruptions
• Volcanoes fall into 3 states
–Active
–Dormant
–Extinct

60. Active Volcano
• Constant volcanic activity
• Currently undergoing eruption or
are expected to erupt in the
future.
• Mt Pinatubo, Philippines; Mt St
Helens, America.

61. Dormant Volcano
• Currently inactive but may erupt
in the near future
• Prolonged period of no volcanic
activity
• Inner magma chamber still hot
and active
• Mt Fuji, Japan

62. Extinct Volcano
• Volcanoes without current seismic
activity
• No geological evidence of eruption in
the past thousands of years.
• Almost no risk of eruption.
• Lake Toba, Indonesia

63. Risks of living near volcanic areas
1.Destruction by volcanic
materials
2.Landslides
3.Pollution
4.Effects on weather

64. Destruction by volcanic materials
• Lava, rock fragments, volcanic bombs (ejected
molten lava blobs)
• Extreme temperatures of projectiles and lava
flow, destroying and killing.
• Inhaling hot gases and ash can also lead to
injury and death.
• With pyroclastic flow, speeds above 80km/hr
can be achieved, making it impossible to
escape.

65. The loss people of Pompei

66. Landslides
• Collapse of a volcanic cone during eruption.
• Downward displacement of previous slide of
volcano.
• Causes large scale damage to infrastructure
and loss of life.
• Settlements near the volcano may get wiped
out totally.

67. Landslide

68. Pollution
• Ash particles and gases released disrupt
human activities over long distances.
• Some gases (Carbon monoxide, Sulphur
dioxide, etc) are harmful to humans
• Fine ash particles captured in the air endanger
planes and cause large monetary loss due to
grounding of flights.

69. Pollution

70. Effects on weather
• Sulphur dioxide reacts with water vapour in
the atmosphere.
• The particles reflect the sun’s energy back into
space.
• This leads to a cooling of surface temperatures
on earth.
• Fall in global temperature might affect plant
and animal life.

71. Let’s attempt an exercise on what we
have covered.
• 15 - 20 minutes,
• Complete all the questions in
Foolscap / space provided
• Good luck

72. Earthquakes
• Caused by sudden release of stored
energy due to movements of crustal
plates.
• Occurs along faultlines as pressure builds
up stress and when the plates slip,
earthquakes are formed.

73. Key Earthquake Terms
• Seismic waves – energy that is released
by earthquakes.
• Focus – the point in the crustal plate
where the seismic energy originates.
• Epicentre – point above the Focus on
earth’s surface. Most of the energy
released travels along the surface of the
earth.

74. • Aftershocks
–subsequent smaller earthquakes that follow
after a major earthquake.
–Could continue to occur months after the
initial earthquake.
–Some aftershocks might be as powerful as
the original earthquake.

75. Depth of Focus
• The depth of focus affects the
impact felt on the surface.
• 2 key types
1. Deep-focus earthquakes
2. Shallow-focus earthquakes

76. Depth of focus
• Deep-focus earthquake
–70 to 700km below surface
–Smaller impact on land
–Most of seismic waves lose their
energy as they reach the surface.

77. Depth of focus
• Shallow-focus earthquake
–70km and above in the crust
–Greater impact on land
–Seismic waves reach surface
quickly and with more energy.

78. Measurement of earthquakes
• Richter scale (Pg31 in textbook)
9?? Destruction impacts thousands of kilometers of land

79. Factors affecting earthquake damage
• Population Density
• Level of Preparedness
• Distance from epicentre
• Time of occurance
• Soil type

80. Population density
– High population density affects more people
– Tendency for high-rise buildings increases damage
– Higher literacy rate in cities mean higher chance
of better preparedness.
• Higher chance of survival
• Better evacuation plans, trained rescue workers.

81. Level of preparedness
• Proper public training and social
awareness leads to less panic
• Repeated practice of emergency
exercise leads to familiarity of action
• Emergency preparedness kits raise
possibility of survival

82. Earthquake Preparedness

83. Distance from the epicentre
• Seismic energy weakens as the
distance increases from the
epicentre.
• Locations further away from the
epicentre suffer less from the
earthquake.

84. Time of occurance
• Time of earthquake determines what
people are doing and whether they are
able to react.
• At night, people are asleep. There is less
time to react.
• In the day, survivors of an earthquake are
able to avoid subsequent accidents.

85. Type of soil
• Loose and unconsolidated (not packed
tightly) soil move more in times of an
earthquake.
• Impact on the buildings on the surface is
greater. Damage is often worse.
• Liquefaction – loose soil flowing like
water.
• Danger of landslides after earthquakes
cause more harm.

86. Earthquake zones
• Tendency for earthquakes to occur
along crustal plate margins.
• Tendency for earthquakes to be
caused when subduction along
destructive plates or slipping of
transform plates

87. Earthquake Zones

88. Hazards of living in earthquake zones
• Tsunamis
• Disruption of services
• Fire
• Landslides
• Loss of lives
• Loss of property

89. Tsunamis
• Tsunami – an unusually large sea wave
• Formed by sudden movement of sea floor
• Possible causes
– Earthquakes at subduction zones
– Explosive underwater volcano eruption
– Underwater landslide
– Large coastal landslides

90. Tsunamis
• As the displaced water moves, it gathers
strength and size.
• When it hits the coast, large destruction is
resulted.

91. Disruption of services
• Loss of electricity, gas and water leads to
loss of essential services.
• Broken pipelines also raise the risk of
explosions.
• Roads and railway destruction make it
harder to send aid.

92. Fire
• Earthquakes at timings where meals are
prepared raise risk of fires.
• Gas pipes and electric cables that are
broken lead to fire risk.
• Urban areas are densely populated,
hence larger fire risk.

93. Landslides
• Shaking of earthquakes loosen soil.
• Along slopes and hills, original vegetation
may no longer be able to hold soil.
• Landslides and mudflows cause large
damage.
• Heavy rainfall after earthquakes raise the
risk of landslides.

94. Destruction of property and
Loss of lives
• Earthquakes destroy homes and buildings that
are not earthquake proof.
• Large amount of money needs to be spent to
rebuild the property.
• Urban areas with more infrastructure (roads,
subways) cause even more money to repair.

95. Part 4
Benefits of living near a Volcano

96. 4 key benefits of living near volcanoes
• Fertile soil
• Precious stones and minerals, building
materials
• Tourism
• Geothermal energy

97. Fertile Soil
• Lava and ash breakdown to form fertile
volcanic soils
• The richest soils on earth, highly
favourable for agriculture
• Hawaii and Bali

100. Precious stones and building materials
• Volcanic rocks can be rich in precious stones
and minerals.
• After the top layers of volcanic rocks are
eroded, these can be extracted.
• The volcanic rocks at Kimberley, South Africa,
are the richest source of diamonds globally.
• Other useful materials like sulphur can be
collected from volcanic rocks. Sulphur is used
to refine sugar and make matches and
fertilisers.

102. Tourism
• Volcanic areas have dramatic landscapes.
• Scenery attracts tourists for hiking and
camping.
• Volcanic areas are rich in history and attract
visitors too.
• The ruins of Pompeii, Italy. The black beaches
in Bali

104. Geothermal Energy
• When groundwater comes in contact with the
hot rocks underground, it heats up and
escapes as steam.
• This can be harnessed to produce Geothermal
Energy.
• Large turbines are used to complete this
process.
• Iceland uses Geothermal energy to power
over 70% of their homes.

106. Part 5 : Responses to
Earthquakes
‘O’ Level only

107. Why do people live in such places?
• Favorable living conditions
–Fertile soil conditions for
agriculture.
• No alternative location to live in.
–Case of no choice

108. Review Question
• Turn to pg 47 of your textbook.
• Using that map, let’s answer the questions in
the handout.

109. 3 approaches to earthquakes
1.Fatalistic approach
2.Acceptance approach
3.Adaptation approach

110. Fatalistic approach
• People who accept earthquakes as
unavoidable.
• Tend to resist evacuation in the face of an
earthquake.
• Common for communities in less
developed countries with limited access
to other places.
• People who live near Mt Pinatubo.

111. Acceptance approach
• People who accept the risk of living in
earthquake-prone areas due to the
benefits of living in that area.
• Benefit outweigh the costs of moving
away.
• Mostly accepted by the developed
countries.
• People of Christchurch.

112. Adaptation approach
• People who successfully live in
earthquake-prone areas as they are well
prepared.
• Use of earthquake monitoring devices,
risk assessment, technology to increase
earthquake resistance.
• Costly approach but able to save many
lives and property.
• People in Taiwan and Japan.

113. Responding to earthquakes