earthquake preparedness

1. Part 3
Landforms commonly associated at
tectonic boundaries

2. Fold Mountains

3. 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.

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

5. Rift Valleys /
Grabens

6. 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

7. Rift Valley diagram

8. Block Mountains / Horst
Yosemite National Park

9. 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

10. Block Mountain diagram

11. Volcanoes

12. 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.

13. • 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.

15. 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

16. 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

17. 2 Key types of Volcanoes
1.Shield Volcanoes
2.Composite Volcanoes
(Stratovolcanoes)

18. Shield Volcanoes

19. 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

20. Stratovolcanoes

21. 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

22. Mt Pinatubo

23. 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

24. Pacific Ring of Fire

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

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

27. 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

28. 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

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

30. 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.

31. The loss people of Pompei

32. 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.

33. Landslide

34. 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.

35. Pollution

36. 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.

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

38. 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.

39. 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.

40. • 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.

41. 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

42. 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.

43. 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.

44. Measurement of earthquakes
• Richter scale
9?? Destruction impacts thousands of kilometers of land

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

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

47. 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

48. Earthquake Preparedness

49. 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.

50. 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.

51. 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.

52. 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

53. Earthquake Zones

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

55. 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

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

57. 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.

58. 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.

59. 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.

60. 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.