This document discusses natural hazards caused by tectonic and climate-related events. It provides details on the internal structure of the Earth, including the crust and mantle. It then focuses on plate tectonics, explaining the three main types of plate boundaries and associated landforms. Specific examples are given for each plate boundary type. The document also addresses causes of earthquakes and their impacts, as well as types and characteristics of volcanoes.

1. Natural hazards
• Tectonic hazards
eg Volcanic
eruptions,
earthquakes
• Climate-related
hazards eg
Typhoons, floods,
droughts

2. Natural hazards - a natural event that threatens human
lives and causes damage to property.

3. b. What is the internal structure of the earth?

4. Crust
• Oceanic crust is found beneath oceans
• Continental crust is found beneath the continents
• Thickness ranges from a few km to more than 70 km
What is the internal structure of the earth?
When the rocks in the mantle melt, hot
molten rock called magma is formed.

5. Oceanic crust vs Continental crust
Oceanic Crust
• Located beneath deep
ocean
• Very thin — between 5
and 8 km
• Denser (e.g. basalt)
Continental Crust
• Located beneath land
masses and under shallow
seas
• Very thick — between 30
and 60 km
• Less dense (e.g. granite)

6. Plates moving away from each other
Platesmoving
towards
eachother
Platesmoving
towardseach
other
Plates
Ocean floor
Why do tectonic plates move?

7. 1. Convection currents
•Material in the mantle is heated by the core.
•Mantle expands, rises and spreads out beneath
the plates.
•Plates are dragged along and move away from
each other.
•Subsequently, the magma cools slightly and
sinks, pulling the plates along
•Hence plates move towards each other.
•The sinking mantle material heats up again as it
nears the core and the whole process repeats.
Why do tectonic plates move?

8. 2. Slab-pull force
• This occurs when an
oceanic plate (denser)
subducts under a less dense
plate and pulls the rest of the
plate along.
• The subducting plate drives
the downward-moving
portion of convection
currents.
• Causes plates to move
towards each other
Why do tectonic plates move?

9. 3 types of plate boundaries

10. Types of
movement
Types of plates Landforms Examples
Divergent -
plates move
away from
each other
Oceanic-oceanic plate
divergence
Oceanic ridges Mid-Atlantic Ridge
Continental-continental
plate divergence
Rift valley,
volcanoes
The Great Rift
Valley
Convergent
- plates
move
towards
each other
Oceanic–oceanic plate
convergence
Oceanic trenches,
volcanoes, island
arc
Mariana Trench,
Mariana Islands,
Hawaii Islands
Continental–oceanic plate
convergence
Ocean trenches,
mountain ranges
Sunda Trench,
Barisan Mountains
Continental–continental
plate convergence
Mountain ranges Himalayas
Transform -
plates move
past each
other
Continental-continental
plates sliding past each
other
None St Andreas Fault

11. Describe the plate movement and
landforms
1) What are the two plates involved?
2) What is the plate movement?
3) What happens at the movement?
4) Is there any construction or
destruction of plates?
5) What are the landforms created?

12. 1. Oceanic-oceanic plate divergence

13. 1. Oceanic-oceanic plate divergence
OceanicOceanic
plateplate
OceanicOceanic
plateplate

14. • Two oceanic plate move away from each other
• As plates diverge, a crack/gap is formed
• Magma rises from the mantle to fill up the gap
• New sea floor is formed when the magma cools and
solidifies. This process is called sea-floor spreading.
• At the zone of divergence/spreading zone, new ocean floor
is formed as the mid-oceanic ridge.
• The newly formed (youngest) rocks are closest to the plate
boundaries.
• At various points along the ridge, magma builds up above
the ocean to form volcanic islands.
• E.g. the Mid-Atlantic Ridge is found in the middle of the
Atlantic Ocean cutting across Iceland, a volcanic island.
1. Oceanic-oceanic plate divergence

15. 2. Continental–continental plate divergence
• Two continental plate moves away from each other
• Results in cracks / fault lines created
• Middle section sinks, while adjacent side remains
• Results in RIFT VALLEY and BLOCK MOUNTAINS

16. • A rift valley is a low land valley with steep sides , and
a flat valley floor formed along fault lines.
• A block mountain is a block of land with steep sides.
It is formed when sections of the crust extend along
fault lines and rock masses surrounding a central
block sink due to tensional forces.

17. • A fault is a fracture in the rocks along which
the rocks are displaced.
• The tensional forces result in parts of the
crust being fractured.
• This process is called faulting.
2. Continental–continental plate divergence

18. EXAMPLES
Linear sea - Red Sea and Gulf
of Aden near the Great Rift
Valley
–Elongated/linear shape
–1,900 km long, 300 km
at its widest stretch,
Average depth of 500 m
–Evidence of tectonic
activity — formation of
new volcanic island in
Red Sea
2. Continental–continental plate divergence

19. EXAMPLES
Great Rift Valley (East Africa)
– formed by Somalian
boundary of the African
Plate moving away from
the Nubia plate boundary
of the African Plate
– 6,000 kilometres long, 30
to 100 kilometres wide
– Evidence of tectonic
activity: active volcanoes
and earthquake fractures
found
2. Continental–continental plate divergence

20. • Distribution of rift valleys and block mountains

21. 3. Oceanic–oceanic plate convergence

22. • Earthquakes may also occur.
• E.g. the Pacific Plate converging with the slower-moving
Philippine plate
3. Oceanic–oceanic plate convergence
OceanicOceanic
plateplate
OceanicOceanic
plateplate

23. 3. Oceanic–oceanic plate convergence
• Two oceanic plates move towards each other
• The heavier oceanic plate subducts under the lighter
plate.
• A subduction zone forms, creating a deep oceanic
trench.
• The subduction of the oceanic plate causes the crust
to melt and magma is formed.
• The magma rises to emerge as volcanoes.
• Eventually a chain or arc of islands called island arc is
formed.

24. Continental crust
Continental crust
Himalayas
Tibetan
Plateau
Uppermost mantle
Asthenosphere
EURASIAN
PLATE
INDIAN
PLATE
4. Continental – Continental plate
convergence
E.g. The Himalayas

25. 4. Continental – Continental plate convergence
ContinentalContinental
plateplate
ContinentalContinental
plateplate

26. • Two continental plates move towards
each other
• Both plates have similar densities and
hence, resist subduction.
• The plates break, slide along fractures in
the crust and fold, forming fold
mountains.
• E.g. the Himalayas - convergence of the
Indian Plate and the Eurasian Plate.
4. Continental – Continental plate convergence

27. 5. Oceanic – Continental plate convergence

28. 5. Oceanic – Continental plate convergence
ContinentalContinental
plateplate
OceanicOceanic
plateplate

29. • An oceanic plate and continental plate moves towards each other
• The denser oceanic plate subducts under the less dense
continental plate.
• A subduction zone forms, creating a deep oceanic trench along
the plate boundary.
• The subduction of the continental plate causes the plate to melt
and magma is formed.
• The magma rises through the mantle and crust to emerge as
volcanoes on land.
• The edge of thick continental plate buckles to form fold
mountains.
• Earthquakes may also occur.
• E.g. the Australian Plate subducting under a section of the
Eurasian Plate near Sumatra formed the Sunda Trench.
5. Oceanic – Continental plate convergence

30. Fold mountains
• Over millions of years, the folding of rocks creates a
landform called fold mountains.
• The Himalayas, the Rocky Mountains and the Andes are
examples of fold mountains.
• Fold mountains are formed along
convergent plate boundaries.
• The compressional force causes
the layers of rocks to buckle and
fold.
• This process is known as folding.

31. Fold mountains
The Himalayas
Peak : Mount Everest (between Nepal and Tibet)
Elevation : 8,848 metres
The Alps
Peak : Jungfrau and Titlis (Switzerland)
Elevation : 4,158m and 3238m

32. • located along convergent plate boundaries
Fold mountains location

33. 6. Transform : Continental – Continental plate slides past each other

34. • Plates slide past each
other.
• As they do so,
tremendous stress
builds up.
• This stress is eventually
released, often as a
violent earthquake.
• E.g. San Andreas Fault,
United States of America
& North Anatolian Fault,
Turkey
6. Transform : Continental – Continental plate slides past each other

35. E.g. San Andreas Fault, United States of America
• In 1906, an earthquake
occurred in San Francisco,
southern California between
the Pacific Plate and the North
American Plate.
– This caused several hundred
km of North American Plate
to move an average of 2.5 m
– and at one point almost 7 m
all in less than 1 minute.
6. Transform : Continental – Continental plate slides past each other

36. E.g. North Anatolian Fault, Turkey
How would the plate movement affect the two cities shown in
time to come?
6. Transform : Continental – Continental plate slides past each other

37. • An earthquake is a vibration in the earth’s crust
caused by the sudden release of stored energy in the
rocks found along fault lines.
Earthquakes

38. The distribution of the earth’s major earthquakes

39. • Apart from its magnitude, the extent of
damage caused by an earthquake may vary
based on other factors:
1. Population density
2. time of occurrence
3. level of preparedness
4. distance from the epicentre
5. type of soil
Extent of damage caused by Earthquakes

40. 1) Population density
• EQ in a city causes more causalities and damages than an
EQ in the countryside.
In 1964, an EQ in Anchorage(Alaska) of magnitude 9.2 had only 115
people died as the area had a small and sparse population.

41. 2) Time of occurrence
• The time of the day which the EQ occurs determines where
people are at and what they are doing, therefore affecting
their chances of survival.
In 1999, when
an EQ struck
after midnight
in Sun Moon
Lake (Taiwan),
more than
2400 died in
their sleep.

42. 3) Level of preparedness
• The more prepared the people are in the event of an EQ
such as evacuation plans and trained rescue workers, the
higher their chances of survival.
In Japan, students are taught in schools how to react when the EQ
warning signal goes. They will move to a safe area in an orderly
manner and not result in a stampede.

43. 4) Distance from epicenter
• The damage caused by an EQ is more severe when an area
is closer to the epicenter of the EQ.
In 2011,
Christchurch had
an EQ of
magnitude 6.3
with 75 deaths
as compared
with 2010’s EQ
of magnitude 7.1
with 0 deaths.
This is due to the
nearer epicenter
to the town in
2011.

44. 5) Type of soil
• Places with loose and unconsolidated sediments may
amplify seismic waves and results in greater damage when
EQ occurs.
In 2011, the EQ in Christchurch (New Zealand) causes liquefaction of
the ground which became unstable and saturated soil flow like
liquid. Houses and buildings had to be abandoned.

45. 1. Threat of tsunamis
2. Disruption of services
3. Fires
4. Landslides
5. Destruction of properties
6. Destruction of infrastructure
7. Loss of lives
SPLIT Like Flower
Damages caused by Earthquakes

46. 1) Threat of tsunamis
• Tsunami refers to an usually
large sea wave.
• Tsunamis may be formed
by:
- The movement of the sea
floor during a large
earthquake at subduction
zones;
- An underwater volcanic
eruption;
- An underwater landslide; and
- A landslide above sea level
which causes materials to
plunge into the water.
In 2004, a 9.2 earthquake in
Indian Ocean triggered a
tsunami that damaged
coastal communities in 12
countries. The tsunami waves
were 4-39m high and went
inland to 10km in western
Sumatra.

48. Tsunami formation

49. 2) Disruption of services
• An earthquake can disrupt services such as the supply of
electricity, gas and water.
In 2004, an earthquake in Kobe, Japan disrupted electricity, gas
and water supplies to the city’s 1.4 million residents.

50. 3) Fire
-Earthquakes may rupture gas pipes and this can provide fuel to
start fires.
In 1995, an
earthquake in
Kobe, Japan
caused
extensive
fires.

51. 4) Landslides
• Landslides are rapid downslope movements of soil,
rock and vegetation.
• Mudflows may also occur when there is heavy
rainfall.
In 1970, an
earthquake in Peru
destabilised the
slopes of Mount
Huascaran and
triggered a massive
landslide. The
landslide travelled at
160km/h and flatten
the town within
seconds. More than
18000 people died.

52. 5) Destruction of properties
• Earthquakes can cause destruction to many homes.
• People may be without homes after the disaster.
In 2011 Tohoku
Earthquake in
Japan, the
tsunami
travelled 10km
inland and
destroyed the
houses and
properties.

53. 6) Loss of lives
• Earthquakes and their associated hazards often
threaten the lives of those living in earthquake zones.
A body of a victim lies trapped in the debris after an
earthquake hit, in Kathmandu, Nepal April 25, 2015. The
earthquake measured 7.9 magnitude.
In 2010, Haiti
Earthquake
killed 300,000
people and left
1.3 million
homeless.

54. 7) Destruction of infrastructure
• Earthquakes may cause cracks to form in infrastructure
such as roads and bridges.
• Transportation can be disrupted as it is unsafe to use the
damaged roads.
In 1995, Kobe’s
earthquake
damaged many
places in the
city where it
became
inaccessible and
difficult to
reach.

55. Examples of major earthquakes and impact

57. Volcanoes
• A volcano is a landform formed by magma ejected
from the mantle onto the earth’s surface.
Mount Saint Helens volcano before and after an eruption in May
1980

58. Video of Active Volcano in Hawaii,
Hilo (December 2016)
http://sendvid.com/946ssyix

59. Parts of a Volcano
Magma chamber, Pipe, Vent, Crater, Caldera, Cone, Ash, Lava

60. Where are volcanoes distributed?
- Pacific Ring of Fire
- Near plate boundaries
- Countries such as Japan and Indonesia Archipelago
- Some volcanoes are in middle of the ocean such as Mauna Loa in Hawaii

61. Shapes and sizes of volcanoes
• Volcanoes vary in shapes and sizes due to the
characteristics of the lava.
• Viscosity refers to the stickiness of the lava
• More viscous = more sticky/ dries faster
• Less viscous = more fluid/ flows further
• The most common types of volcanoes are:
- Shield volcanoes
- Stratovolcanoes
Volcanoes

62. Shield volcanoes
• Gradient : gently sloping sides
• Height : Shorter
• Viscosity : Less viscous, lower silica content
• Eruption : Less violent

63. Shield volcanoes
- Chain of volcanoes in Hawaii
- No presence of plate boundaries

64. Video of Active Volcano at Jagger
Museum (Hawaii, Hilo) December 2016
http://sendvid.com/9gmednua

65. Stratovolcanoes
• Gradient : Sleep sloping sides
• Height : Taller
• Viscosity : More viscous, higher silica content
• Eruption : More violent (trapped gases)
• Eg. Mount Mayon, Philippines

66. Volcanoes
Active, dormant or extinct
• Active volcanoes refers to volcanoes which are currently
erupting or are expected to erupt in the future.
• Dormant volcanoes are currently inactive but may erupt
in the near future.
• Extinct volcanoes refers to volcanoes without current
seismic activity

67. 4 Risks of living near volcanic areas
• Destruction by volcanic materials
• Landslides
• Pollution
• Effects on weather

68. 1) Destruction by volcanic materials
• Lava 500°C to 1400 °C
• Pyroclasts (ash, rock fragments and volcanic bombs)
are produced
In 1985, the eruption
of the Nevado del
Ruiz in the Andes
Mountain (South
America), released a
pyroclastic flow. The
lahar engulfed the
town of Armero and
killed more than
20,000 people.

69. Hawaii
Volcano
National Park

71. Pyroclastic flow
Destructive mass of
very hot ash, lava
fragments, and gases
ejected explosively
from a volcano and
typically flowing at
great speed.

72. Video of Volcano steam at the ocean ,
Hilo (Hawaii) December 2016
http://sendvid.com/7948sl5l

73. Jagger Museum, Hawaii

74. Lahar
A type of mudflow or
debris flow composed of
a slurry of pyroclastic
material, rocky debris,
and water.
The material flows down
from a volcano, typically
along a river valley.

75. 2) Landslides
• occur due to the structural collapse of a volcanic cone.
• obstruct the flow of rivers which causes floods,
• block roads, bury villages and farmlands.
In 1980, eruption
of Mt St Helens in
Washington
created the largest
landslide which
flattened 150,000
acres of fir trees.

76. Lua Manu
Crater
(erupted in
1974)

77. 3) Pollution
• Ash particles may block sunlight, suffocate crops, and cause
severe respiratory problems for people and animals.
• Release of gases may be harmful to people.
During AD 79, Mt.
Vesuvius (Italy)
erupted and
expelled a deadly
cloud of volcanic
gas, stones, ash
and fumes that
rose to a
tremendous height
of 33km.

78. Jagger
Museum,
Hawaii

79. 4) Effects on weather
• Sulphur dioxide released from volcanic eruptions has
impacts on the environment
• It may react with water vapour and other chemicals in the
atmosphere to form sulphur-based particles.
• These particles reflect the sun’s energy back into space and
temporarily cool the earth for periods of time.
In 2010, the Iceland
volcanic eruption
producted volcanic ash
clouds which were a
danger to aircraft
engines. This result in a
closure of airspace
where flights were
cancelled.

80. 4 Benefits of living near volcanic areas
• Fertile volcanic soil
• Building materials, and precious stones and
materials
• Tourism
• Geothermal energy

81. 1) Fertile volcanic soil
• Lava and ash from the volcanic eruptions break down to
form fertile volcanic soils. Favourable to agriculture
The volcanic soils of Java
and Bali in Indonesia
support crops such as
tea, coffee and rice as
the soils are fertile due
to lava and ash.

82. 2) Precious stones and minerals, building materials
• Volcanic rocks can be rich in precious stones and minerals.
• These resources can only be from a volcanic area after
millions of years.
• An example is diamond.
The old volcanic rocks at
Kimberly in South Africa are
one of the world’s richest
sources of diamond.

83. 3) Tourism
• Volcanic areas offer a variety of activities for tourists to
engage in.
The ruins of Pompeii (Italy) was
buried by layers of ask from
nearby Mt Vesuvius when it
erupted. 3 million tourists visit
yearly to see remains of
buildings and pottery.

85. 4) Geothermal energy
• Geothermal energy is derived from the heat in the earth’s
crust.
• The hot water or steam can be harnessed to produce
electricity.
Most of Iceland’s electricity is
generated from geothermal
power which hot water or
steam is harnessed to drive
turbines.
Hakone (Japan) attracts many
tourists due to the hot
springs that are from volcanic
steam