Chapter 1: Living with Tectonic
Part 1: Hazards of the world
Copy when you see the star
What is a Natural Hazard
• Is it possible for Singapore to experience an
• 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.
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.
– When driving
– At the shops
• You will have to answer the worksheet after
watching the video so pay attention.
Let’s now attempt the exercise
• You have 10 minutes to
answer the questions on the
• Good luck!
What is the structure of the Earth?
•Crust Read up on Pg 7
in your textbook
• The crust of the earth.
• Two general types
• Less Dense, heavier
• Denser, lighter
• Theory that crustal plates are constantly
• 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.
Continental Drift Diagram
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
Continental Drift Diagram
• Watch the following video on Colliding
• Answer the questions in the SRP handout /
complete the groupwork
• 50 mins National Geographic video
Types of plate boundaries
• Convergent plate boundary
• Divergent plate boundary
• Transform plate boundary
• Refer to pg 9 textbook
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.
Diagram of Divergent plate boundary
(insert water surface for oceanic)
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
• What do you think is needed to answer this
– “ 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.
Part 2: Convergent plates
• If there are plate boundaries that are
diverging, at the end of that plate, there
will be convergence.
• 3 common types of convergent
–Oceanic vs Oceanic plate
–Oceanic vs Continental plate
–Continental vs Continental plate
Reasons for convergence
• Plates converge due to continental drift.
• As the plates are pushed apart, they crash into
• 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.
• Beneath deep oceans
• Between 5km and 8km
• Consists of basalt
• Very dense and heavy
• Made of young rock (200 million years ago)
• 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.
Oceanic-oceanic plate boundaries
• When two oceanic plates converge
• Denser plate subducts under the less dense
• Area where it subducts is called the
• 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
Oceanic-oceanic plate boundaries
Oceanic-Continental plate convergence
• When an oceanic plate converges with a
• The dense oceanic plate is forced down into
• 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
Continental-Continental plate convergence
• When two equally dense continental plates
• 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
• At such plate boundaries, large mountain
ranges tend to form. (Himalaya)
Continental –continental plate
• Occurs when plates slide past one
• Huge energy released when friction is
• Large massive earthquakes experienced
• San Andreas Fault (California)
• Take a look at the handout (exercise 2).
• Using the information you have learnt so far,
answer the question to the best of your
• Good luck
Review Comparison Table
Plate boundary type Associated landforms Example
Oceanic-Oceanic Deep sea ridge Mid-Atlantic Ridge
Continental-Continental Rift Valley Great African Rift Valley
Oceanic-Oceanic Deep Sea Trench, Volcanoes,
Mariana Trench, Mariana
Islands, Pacific plate and the
Oceanic-Continental Deep Sea Trench, subduction
zone, Volcanoes, Fold
Sunda Trench, Barisan
mountains, Australian plate and
the Eurasian plate
Continental-Continental Deep sea trench, subduction
zone, fold mountains
Himalayas, Eurasian plate and
the Indian plate
Landforms commonly associated at
• 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.
• The major ranges are along
convergent plate boundaries
• The rocky mountains
• Swiss Alps
• Pg 22
Rift Valleys /
• Near divergent plate boundaries, plates pull
apart, causing land displacement.
• The downward displacement forms rift
• Found commonly along divergent boundaries
• Also called Graben
• East African Rift Valley
Rift Valley diagram
Block Mountains / Horst
Yosemite National Park
• When sections of the crust are pulled
apart by tensional force, some parts are
• The downward displaced areas are the
• The blocks left behind form block
mountains with steep sides.
• Also called Horst
Block Mountain diagram
• Landform formed by magma ejected from the
• Magma builds up in the earth’s crust to form a
• With repeated layering of ejected magma, the
volcano grows in height
• Found a divergent and convergent plate
boundaries where there is subduction.
• Vents are openings in the earth’s surface
with a pipe leading into the magma
• 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.
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
• 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
2 Key types of Volcanoes
• Gentle sloping sides and a broad
• Low-silica lava (low viscosity) present
• Lava flow is fast, spreading out
• Subsequent layering leads to wide
base with low overall height.
• Mount Washington in America
• Developed from successive eruptions.
• Ash and lava (coarse fragment) accumulate over
• Layers of ash are locked in by subsequent layers of
• 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
Distribution of volcanoes
• Pacific Ring of Fire is the most active volcanic
• Many earthquakes and volcanic eruptions
occur along the ring of fire
• Ring is along several converging plates (Pacific,
Nazca, Philippines, Australian and Eurasian
• Volcanoes can also form where plates diverge.
• Pg 29
Pacific Ring of Fire
• Volcanoes fall into 3 states
• Constant volcanic activity
• Currently undergoing eruption or
are expected to erupt in the
• Mt Pinatubo, Philippines; Mt St
• Currently inactive but may erupt
in the near future
• Prolonged period of no volcanic
• Inner magma chamber still hot
• Mt Fuji, Japan
• Volcanoes without current seismic
• No geological evidence of eruption in
the past thousands of years.
• Almost no risk of eruption.
• Lake Toba, Indonesia
Risks of living near volcanic areas
1.Destruction by volcanic
4.Effects on weather
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
The loss people of Pompei
• Collapse of a volcanic cone during eruption.
• Downward displacement of previous slide of
• Causes large scale damage to infrastructure
and loss of life.
• Settlements near the volcano may get wiped
• 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.
Effects on weather
• Sulphur dioxide reacts with water vapour in
• The particles reflect the sun’s energy back into
• This leads to a cooling of surface temperatures
• Fall in global temperature might affect plant
and animal life.
Let’s attempt an exercise on what we
• 15 - 20 minutes,
• Complete all the questions in
Foolscap / space provided
• Good luck
• Caused by sudden release of stored
energy due to movements of crustal
• Occurs along faultlines as pressure builds
up stress and when the plates slip,
earthquakes are formed.
Key Earthquake Terms
• Seismic waves – energy that is released
• 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
–subsequent smaller earthquakes that follow
after a major earthquake.
–Could continue to occur months after the
–Some aftershocks might be as powerful as
the original earthquake.
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
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.
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.
Measurement of earthquakes
• Richter scale (Pg31 in textbook)
9?? Destruction impacts thousands of kilometers of land
Factors affecting earthquake damage
• Population Density
• Level of Preparedness
• Distance from epicentre
• Time of occurance
• Soil type
– 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.
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
Distance from the epicentre
• Seismic energy weakens as the
distance increases from the
• Locations further away from the
epicentre suffer less from the
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.
Type of soil
• Loose and unconsolidated (not packed
tightly) soil move more in times of an
• Impact on the buildings on the surface is
greater. Damage is often worse.
• Liquefaction – loose soil flowing like
• Danger of landslides after earthquakes
cause more harm.
• Tendency for earthquakes to occur
along crustal plate margins.
• Tendency for earthquakes to be
caused when subduction along
destructive plates or slipping of
Hazards of living in earthquake zones
• Disruption of services
• Loss of lives
• Loss of property
• 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
• As the displaced water moves, it gathers
strength and size.
• When it hits the coast, large destruction is
Disruption of services
• Loss of electricity, gas and water leads to
loss of essential services.
• Broken pipelines also raise the risk of
• Roads and railway destruction make it
harder to send aid.
• 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.
• Shaking of earthquakes loosen soil.
• Along slopes and hills, original vegetation
may no longer be able to hold soil.
• Landslides and mudflows cause large
• Heavy rainfall after earthquakes raise the
risk of landslides.
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.
Benefits of living near a Volcano
4 key benefits of living near volcanoes
• Fertile soil
• Precious stones and minerals, building
• Geothermal energy
• Lava and ash breakdown to form fertile
• The richest soils on earth, highly
favourable for agriculture
• Hawaii and Bali
Precious stones and building materials
• Volcanic rocks can be rich in precious stones
• 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
• Volcanic areas have dramatic landscapes.
• Scenery attracts tourists for hiking and
• Volcanic areas are rich in history and attract
• The ruins of Pompeii, Italy. The black beaches
• When groundwater comes in contact with the
hot rocks underground, it heats up and
escapes as steam.
• This can be harnessed to produce Geothermal
• Large turbines are used to complete this
• Iceland uses Geothermal energy to power
over 70% of their homes.
Part 5 : Responses to
‘O’ Level only
Why do people live in such places?
• Favorable living conditions
–Fertile soil conditions for
• No alternative location to live in.
–Case of no choice
• Turn to pg 47 of your textbook.
• Using that map, let’s answer the questions in
3 approaches to earthquakes
• People who accept earthquakes as
• Tend to resist evacuation in the face of an
• Common for communities in less
developed countries with limited access
to other places.
• People who live near Mt Pinatubo.
• 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
• Mostly accepted by the developed
• People of Christchurch.
• People who successfully live in
earthquake-prone areas as they are well
• Use of earthquake monitoring devices,
risk assessment, technology to increase
• Costly approach but able to save many
lives and property.
• People in Taiwan and Japan.
Responding to earthquakes
Watch video on youtube (news report on Sgp experiencing tremors April 2012) click on lightning to open link.http://www.youtube.com/watch?v=7Eb8xYbF_Po
Video on Japanese emergency action training http://www.youtube.com/watch?v=IaedDlN5dfoWatch once, then at kids request restart at techniques (around 3 min mark) before giving exercise.
Draw Continental Drift Theory Diagram.
http://www.youtube.com/watch?v=ryrXAGY1dmE1m 14 sec vid on continental drift
Draw oceanic divergent plate diagram
Draw diagram of continental –continental divergence
Video on Oceanic vs Continental plate, buckling, forming mountains and Tsunami occuring prior to reset.http://www.youtube.com/watch?v=ep2_axAA9Mw
http://www.youtube.com/watch?v=7LgZThrw9DMWatch from 7.00 to 8.00 to see deformed diagram and misguided truth about Japanese Trench.
Click on picture to show 3 min vid on San Andreas Fault (National Geographic)http://www.youtube.com/watch?v=ZxPTLmg0ZCwWatch also the next clip on the damage to roads to LA after 94 quake click on Agent Phttp://www.youtube.com/watch?v=mcoHJHo8d6kFinal additional clip of a classroom destroyed during a quake http://www.youtube.com/watch?v=FW-TkpvKPl0
Refer to Unit 1 Ex 2 (map of plate boundaries and Qn on possible phenomena at 3 such boundaries).
Click on picture to watch 2 min vid on top 10 active volcanoes in the world
Watch 6min vid on Mt St Helen eruption 1980s.http://www.youtube.com/watch?v=-H_HZVY1tT4
Honey – high viscosityWater – low viscosity
Watch video on Mt Pinatubo eruption Human impacthttp://www.youtube.com/watch?v=NQzGjGKdGvQ (4 min)Or
Watch video on Pacific ring of fire (10 mins)http://www.youtube.com/watch?v=YqSJDNi7Qzw
Watch 2.25 min video footage of the plaster cast people of Pompeihttp://www.youtube.com/watch?v=8P352045O-oHighlight that these people were instantly turned into plaster casts by the pyroclastic flow.
Watch video on the landslide after Mt St Helen’s eruptionhttp://www.youtube.com/watch?v=UK--hvgP2uY2 min vid
Watch FOX news rpt on Iceland volcanic eruption grounding flightshttp://www.youtube.com/watch?v=RCWp1fGP_6M3 minsAlJazeera clip on Heathrow opening and passengers stranded in SGP flying backhttp://www.youtube.com/watch?v=WfcTMlP5UTA
Issue Ex 5 on the negative effects of living near a volcano
Watch view of destruction post earthquake in Christchurch(2min)http://www.youtube.com/watch?v=opsiKirDfdENews report on Christchurch massive quake (response by gvt)(1:30 min)http://www.youtube.com/watch?v=wBq1-qZWmhM
Watch NZ video on Earthquake Preparedness(4min)http://www.youtube.com/watch?v=-a7T9Uf-JB4
Watch clip on tremors in SGP (who is our buffer?) Indonesia!http://www.youtube.com/watch?v=7Eb8xYbF_Po
Watch video of damage of 7.2 Christchurch earthquake 2011. End of vid, ask students to think if it had happened in the middle of the night, what might the death toll be looking at the look of the damage in the video?http://www.youtube.com/watch?v=jlykXk82BlY(3min)
Watch short clip on liquefaction (45 secs)http://www.youtube.com/watch?v=qmVYbjiNWdsAlternate vid (forward to 50s) to watch the video of liquefaction.http://www.youtube.com/watch?v=PwvvYxSZ7PI
Pic on left (vid) that shows 2004 Tsunami at Thailandhttp://www.youtube.com/watch?v=ntIwawAusDEPic on right (vid) of Bandar Aceh (initial earthquake and subsequent tsunami) 7 min. Worth watching!http://www.youtube.com/watch?v=ht_ZpSuJ6A4
Watch 3 min vid on Japanese earthquakehttp://abcnews.go.com/Archives/video/jan-17-1995-earthquake-japan-9421417#nightearthquake #fire #JapanEarthquake #destruction
Video of rice fields in Balihttp://www.youtube.com/watch?v=Z83XgZzEOpY
Watch video on blood diamonds , negative effect of having diamonds in the groundhttp://www.youtube.com/watch?v=0hCl_RXqoZk
Watch video on Geothermal energy productionhttp://www.youtube.com/watch?v=rfUQy86ZMpQ