Answers and Suggested Responses—
Chapter 5 Disasters
Opening spread
6.1 What impact do tectonic disasters have?
1
The effects of earthquakes tend to be felt over a larger area than the effects of volcanic eruptions.
Earthquakes also occur much quicker than eruptions with much less warning to residents. In
earthquakes many people may be killed as buildings collapse.
2
They both occur at the edges of plate boundaries and are the result of movements within the
Earth’s mantle and crust.
3
Answers will vary but two common answers will be: ‘I gotta get outa this place!’ and a roar like the
sound of a fright train approaching.
6.2 How do weather disasters affect communities?
1
Storms, hurricanes/cyclones, floods, droughts, lightning strikes, snow storms, hail, typhoons,
heatwaves, bushfires and freezing temperatures.
2
We experience few tectonic disasters because we are located far from the edge of a tectonic plate.
However, we experience many weather disasters because the size of the continent means that it
lies within several climatic zones. It is quite common, for example, for northern regions such as
Queensland to be experiencing floods while parts of southern Australia are experiencing droughts,
heatwaves and bushfires.
3
Drowning, being crushed by blown debris or collapsing buildings, illness from water-borne
diseases, homelessness, disruption to food supply and other essential services.
6.3 What problems do man-made disasters cause?
1
The smoke plume carries soot, which settles on the ground; smoke will block sunlight causing
problems for plants and animals; uncapped oil wells will also mean that oil can escape and settle in
ponds.
2
Destruction of whole ecosystems such as forests; compaction of soils due to the use of heavy
machinery; pollution of air from tanks, planes, etc; water pollution from destroyed ships; destruction
of human environments, such as roads, electricity supplies, bridges and whole towns.
3
Nuclear accidents at Chernobyl and Three Mile Island, ozone depletion, climate change, oil tanker
Exxon Valdez in Alaska are all environmental disasters that were accidents.
Section 6.1 What impact do tectonic disasters have?
What do you know about earthquakes?
1
a United States, Mexico, New Zealand , Indonesia, Philippines, Japan, China, Pakistan and Iran
all experience frequent earthquakes.
b Most of these countries have converging plate boundaries.
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2
Changes to the natural landscape
Changes to communities
‘Mountains and rivers changed places’
Floods
Ground movement resulting in hill and valley
formation
People crushed to death
Streams burst their banks
Homes, temples, city walls and statuses destroyed
Landslides blocked roads
Severe injuries
Dam wall cracked
People displaced from their homes
Collapse of chemical plant
3
They both occurred in China and both resulted in many deaths, mainly from crushing. There were
also changes to river courses in both earthquakes but in the earlier quake in Shaanxi there
appears to have been more changes to shape of the land.
4
Low quality housing tends to collapse more readily during an earthquake, putting the residents at
greater risk from injury and death. The building materials are also important as brick structures
tend to crack and fall apart whereas wooden buildings which are more flexible often survive an
earthquake intact. Housing quality varies around the world due to the building materials available
and the available income of residents. Poor quality housing tends to occur in low income regions.
5
The epicentre is the point on the Earth’s surface directly above where the earthquake begins and is
therefore the point at which the earthquake is felt first and most strongly. The city of Yingxiu lies
close to the epicentre of the Sichuan earthquake and it suffered extensive damage to roads and
buildings and more than three-quarters of the population died.
6
The Richter Scale is used to measure the intensity of an earthquake. It is important to know
earthquake intensity as it helps to compare earthquakes and to learn how to design buildings and
structures to withstand them.
What do you know about tsunamis?
1
Tsunami means ‘harbour wave’ in Japanese and they are no longer called tidal waves because
they are not usually caused by tides.
2
A massive earthquake caused an undersea landslide. This is a tectonic event because the
earthquake resulted from the movement of tectonic plates (the Indo-Australian plate and the
Eurasian plate).
3
Visual answer.
4
The distance is about 1500km, which means that the tsunami travelled at 750km/hr.
5
At sea, a tsunami has very little impact and the fishermen would only feel at slight rise in sea level
as it passed beneath their boat.
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6
Because of the long-term impacts to food production, water supplies and livelihoods through, for
example, the destruction of fishing boat fleets.
7
Tilly noticed that the water was frothing and had receded quickly. She quickly told her parents and
the beach was evacuated.
What do you know about volcanic eruptions?
1
One tectonic plate dives down (subducts) beneath another. In the case of the 1815 Tambora
eruption, the Indo-Australian plate subducted beneath the Eurasian plate. This causes hot magma
to rise to the Earth’s surface and erupt through a weakness in the Earth’s crust.
2
Molten boulders can be thrown many kilometres, ash and gas clouds, pyroclastic and lava flows,
tsunamis and lahars.
3
They build up the Earth’s surface as the ash settles and the lava hardens, particularly near the
crater.
4
Pyroclastic flows are superheated flows of ash, rocks and gases that sweep down the side of a
volcano. The Mayon pyroclastic flow caused no loss of life because no one lived in the area of the
flow or they evacuated the area.
5
Indonesia, New Zealand and Papua New Guinea
6
Refugees may flee to Australia. Australia may be asked to contribute to rescue efforts or to supply
aid to help the survivors recover from the effects of the eruption. Ash clouds may affect our climate.
7
148 000
8
New Zealand was uninhabited in AD 180.
Big Ideas
1
Visual answer.
2
Australia is not located on a plate margin, which is where most earthquakes and eruptions occur.
3
One of the reasons was the standard of buildings that collapsed when the earthquake struck. It is
difficult to compare this to the Newcastle earthquake as this was much smaller, but better building
standards may have resulted in fewer deaths in this instance.
4
Ash can create dangerous pyroclastic flows on the sides of the volcano and ash clouds can stay in
the atmosphere for months, causing changes to climate and bringing about starvation and disease.
Lava flows down the side of the volcano, sometimes quickly but usually quite slowly. Ash causes
the greater loss of life because its effects are more widespread and can occur at a global scale.
Lava effects tend to be only felt at the local scale.
5
a Yingxiu, GR139343
b 2648 deaths, hundreds buried. Many of these victims were children trapped when school
buildings collapsed
c 133 km
d The epicentre was in a mountainous region but the effects of the earthquake were felt on a
neighbouring plain in the south and east as well as in the mountains to the north and west.
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e
The greatest death toll was in the city of Yingxiu because it lies close to the earthquake’s
epicentre.
6
Massive
earthquake
off the
southern
coast of
Sumatra
Undersea
landslide
Water is
pushed
upwards
creating a
large wave
The waves
radiated
outwards
and travelled
towards
coasts
Waves slam
into coastal
towns and
villages
causing great
devastation
7
Overlay map, ensure that both maps have BOLTSS.
a There is a strong spatial association between plate boundaries and earthquakes. Most
earthquakes occur at plate boundaries, particularly where one plate is subducting beneath
another.
b The Sichuan earthquake measured 7.9 on the Richter Scale.
8
Sketch of Kalutara Beach
9
Tsunami warning sign.
10
Changes include loss of beach sand, loss of vegetation including large trees, road destroyed,
flooding, and destruction of buildings including houses. Some loss of life seems likely as a number
of buildings have been destroyed.
11
Features unique to earthquakes: the ground shakes
Features unique to volcanic eruptions: ash cloud
Features unique to tsunamis: large wave
Features common to earthquakes and eruptions: Mostly felt at plate margins
Features common to earthquakes and tsunamis: Effects can be felt over a wide area, flooding,
effects spread out like ripples on a pond.
Features common to eruptions and tsunamis:
Features common to all three: very destructive with great loss of life, strike with little warning, occur
as the result of tectonic movements
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12
Answers will vary but better answers will include the concept of sustainability. This refers to
whether or not the plan will succeed in the long term and whether or not the materials, costs and
expertise are available.
Section 6.2: How do weather disasters affect communities??
What do you know about flooding?
1
Because it has flooding so often throughout history.
2
Because the river provides resources that people need such as a supply of fresh water. The
regular flooding of the river has built up a fertile floodplain which sustains crops and the river also
provides a transport route and a source of electricity.
3
Over time the bed of
the river has risen
higher due to regular
flooding.

Heavy rains in
western China filled
the river to capacity.

Earthen banks, built
to control floods
could not hold back
the force of the river
and burst allowing
water to flood the
plain.

Disease and famine
then set in as
drinking water
became
contaminated and
farming was
disrupted.
Legend:

Natural processes
100 000 km² of
surrounding land was
flooded, destroying
many communities
and covering the
countryside with
water and soil.

Attracted to the
supply of fresh water
and fertile soils,
millions of people
have made the
floodplain their
homes.
Human activities
4
Poorer people had built their homes on marginal land on steep hillsides. These areas were hardest
hit in the floods. Their homes were also poorly constructed so they could not withstand the force of
the water and mud. Poorer people also find it more difficult to recover from natural disasters.
5
They both began with heavy rain in the mountain which swept down rivers into low lying areas. The
natural processes of flooding along with erosion and transportation of silt occurred during both
floods. The effects of the flood were due to a combination of human activities and natural
processes.
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What do you know about cyclones?
1
They are the same naturally occurring event. They are called cyclones in Australia and the Pacific
region, and hurricanes in the Americas (including the west coast) and the Atlantic region.
2
The location of Bangladesh at the head of the Bay of Bengal makes it particularly susceptible to
cyclones. The waters are warm and strong monsoonal winds blow up the Bay. Cyclones also tend
to be funnelled to Bangladesh by the shape of the surrounding land.
3
Criteria
Cyclone Bhola
Hurricane Katrina
Wind speed
185 km/hr
200 km/hr
Storm surge
10 metres
9 metres
Deaths
300 000–500 000
1800
Homeless
3 million
500 000
According to these criteria, Cyclone Bhola was the most destructive.
4
A levee is ‘a raised area between low-lying land and a body of water, built to protect flooding’ (see
glossary, page 304). During Hurricane Katrina, some of these levees collapsed, allowing low-lying
parts of New Orleans to be flooded. The dark area in the second satellite image shows the extent
of the flooding. Attempts were made to repair the levees by using helicopters to lower giant
sandbags into the gaps.
5
Some of the similarities include heavy rain, rivers bursting their banks, people killed and buildings
destroyed by rising waters and problems with disease and food supply after the event. In a
cyclone, winds and rising seas make the situation much worse.
What do you know about Australia’s biggest weather disaster?
1
Important factors include high temperatures, strong northerly winds, mild winters, eucalypt forests
and an ignition such as lightning.
2
Causes
Effects
Responses
High temperatures
71 deaths
Evacuations
Strong northerly winds
20 000 km² burnt
Fire-fighting
Homes and towns destroyed
Establishment of DSE
CFA formed
Towers and roads built
Fuel reduction burning
3
a Changes in equipment, water used today, today’s system is safer as the fire fighter is not near
the fire and is better able to get away if the situation becomes more dangerous.
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b New fire-fighting groups, such as the Department of Sustainability and the Environment and the
Country Fire Authority, were established. Infrastructure was built such as fire towers and fire
access roads. Fuel reduction burns were lit in winter and spring.
c Answers will vary but remind students that changes to fire fighting methods such as the use of
helicopters is one of the options they should consider.
4
Australia’s worst disaster resulted in many fewer deaths than the world’s worst floods and
cyclones. They also affected many fewer people and their long-term effects were not so great.
They are similar, however, to floods and cyclones as they cause loss of life, are due mainly to
natural factors and result in major disruptions to people’s way of life.
Big Ideas
1
A storm surge is the rise in sea level that is caused by strong onshore winds and low atmospheric
pressure that typically accompany a cyclone. It is so destructive because it causes the flooding of
low-lying coastal areas where many cities and communities have been established.
2
A heatwave is a long period of unusually hot weather and they cause the deaths of many people,
particularly the very young or very old. In Australia, they may create the ideal conditions for a
destructive bushfire.
3
Most of the world is largely unaffected by cyclones. Virtually all of the world’s cyclones begin in two
broad bands within the tropics north and south of the equator. In the northern hemisphere, most
cyclones begin in the western Pacific Ocean near the Philippines in Asia and the eastern Pacific off
the coast of Northern America. There are also significant numbers that begin in the northern
Atlantic and the Bay of Bengal. From their point of origin they tend to move in a north-westerly
direction. In the southern hemisphere, the Indian Ocean and the western Pacific off the coast of
Australia are most likely to see the beginnings of cyclones. Cyclones in these areas tend to track in
a south-westerly direction. Cyclones occur in these regions as this is where the ocean and
atmosphere are warm enough.
4
Arson and the building of homes in bushfire prone areas.
5
A cyclone can lead to flooding and an earthquake can cause floods, landslides and tsunami. A
tsunami can also be created by a volcanic eruption.
6
The 1939 bushfires affected large areas of Victoria, particularly the alpine areas north-east of
Melbourne as far as the New South Wales border. The Otway Ranges and area in the south-west
of the state near the city of Portland were also affected. Towns in the alpine regions are Woods
Point, Healesville, Jamieson and Corryong. The Otway Range fires would affect the towns of
Apollo Bay, Lorne and Forrest, while Portland, Heywood and Casterton may have been adversely
affected by the fires in the south-west.
7
Population density remains relatively low in the west of China which is much more mountainous
than the east. The most densely populated areas are the Sichuan Basin in central China where the
Yangtze River leaves the mountains and the coast, particularly on river mouths. The coastal plain
formed by the regularly flooding of the Huang He River is very densely populated and contains
many cities of over 1 million people. People have been attracted to this area by the fertile soils, flat
land and reliable supply of fresh water.
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8
Plant trees suitable distances apart, do not plant them close to the home, use small shrubs such as
succulents in gardens close to the house, pave areas close to the house and keep the areas under
trees free of dried leaves.
9
Visual answer.
10
Helicopters can access areas that may be flooded or impassable to ground transport and can land
in relatively small areas. They can also be used to evacuate people quickly, to deliver essential
supplies such as medicines and fresh water and can provide access for rescuers.
11
A human activity that may contribute to flooding is the building of earthen banks and levees beside
rivers and the settlement of areas for farming and cities next to large rivers. Coastal communities
may also be at risk from the flooding caused by a storm surge. Natural processes are mostly
responsible for large floods as they are caused by heavy rains and the natural tendency of rivers to
leave their normal course and flood across surrounding plains.
12
I have defined ‘worst’ as being the natural disaster that has caused the greatest loss of life.
According to this definition, the 1931 flooding of the Huang He River which claimed over one
million lives has been the world’s worst natural disaster. In addition to this loss of life, more than 80
million people were made homeless.
13
Possibilities include people ignoring warnings or believing that they had prepared adequately,
unexpected events such as the failure of the levees, poor preparations, inadequate infrastructure,
worsening conditions, and unexpected human responses such as looting.
6.3 What problems do man-made disasters cause?
What do you know about deliberate disasters?
1
The Gulf War was fought because Iraq invaded Kuwait, an oil-rich country in the Middle East. Iraq
considers Kuwait to be a part of its territory but other countries, including the United States, does
not. These countries therefore attacked the Iraqi troops in Kuwait.
2
Crude oil released into the waters of the Persian Gulf, oil well fires, use of depleted uranium bullets
and rounds of ammunition, oil seepage into surrounding desert areas, salt water destroyed many
land habitats, compaction of soil due to heavy machinery, land mines and leaking oil from
destroyed warships.
3
It might slow down the coalition forces attacking them; it would distract these forces from attacking
the Iraqi troops by taking resources away from the battle. It would also give them revenge against
the Kuwaitis and against the Americans who they felt only came to battle in order to gain access to
the oil wells.
4
The effects of oil in a marine environment, particularly on sea birds such as penguins.
5
Some of the similarities are that the floods occurred in the same areas because they were both the
result of flooding of the Huang He River; both floods occurred as a result of heavy rain and a failure
of the earthen banks that hold back the swollen river; both floods resulted in the deaths of many
people and the flooding of vast areas of the Chinese countryside. The two floods differ, however, in
one key aspect: the 1931 floods were a natural disaster, whereas the 1938 floods were the result
of a deliberate human act: the destruction of one of the dykes.
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6
Following the retreat of the Iraqi forces back into Iraq and the withdrawal of the coalition forces to
their home countries, the people of Kuwait still had to deal with many environmental issues, such
as the oil spill, oil well fires and ruined desert and marine habitats. Perhaps most worrying,
however, are the land mines that still pose a great threat to people in the country today. In China in
1938, the act of war that slowed the advance of the Japanese troops resulted in the deaths of tens
of thousands of Chinese peasants who became innocent victims of the war and of their own
government’s tactics in that war. After this war, the surviving civilians would also have long-term
effects to cope with, such as the flooding of their fields and the destruction of their homes.
What do you know about the Chernobyl environmental disaster?
1
The Chernobyl nuclear power plant exploded because a routine check of the safety systems went
wrong.
2
6 figure grid reference
Feature on map
How this would be
affected by the
accident within the first
week
How this would be
affected by the accident
for many years
196697
Pripet
Many people affected by
radioactive fallout. Town
evacuated.
Pripet is still an
abandoned town. High
levels of radioactivity still
present.
285676
Radinskoye Forest
Radioactive material
would fall from the
atmosphere
Soil and water would be
contaminated and this
would result in high levels
of radioactivity in plants
298697
Nuclear power plant
Destroyed by explosion
and fire
No longer functions as a
power plant the reactor is
now encased in concrete
306684
Pripet River
Radioactive material
would fall into the river
Water would remain
affected as would the silt
in the river bed. This
would affect plants and
animals, including people.
323672
Kyiv Reservoir
Radioactive material
would fall into the
reservoir and be carried
there by the Pripet River
Water would become
contaminated which
affect people who use
this for domestic supply
and also farmers may
irrigate with this water
further spreading the
contamination.
285692
Staraya Krasnitsa
garden plots
Radioactive material
would fall from the
atmosphere
Soil, water and plants
would become
contaminated and this
would result in affected
crops for many years and
poor health for those who
ate them.
310695
Track in vegetation
Radioactive material
would fall from the
atmosphere
Vegetation would be
contaminated due to
contaminated water and
soil.
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3
People were evacuated because the radioactive material produced in a nuclear explosion is
dangerous to heath and can result in death.
4
They may be many reasons for tensions such as these. The two groups come from different parts
of the country and may have different belief systems or ethnicity. The evacuees often cause a
strain on local resources, such as food and water supplies, and this is felt by new arrivals and longterm residents alike. Many people in the city would also be afraid that people evacuated from
affected areas may spread contamination into their city.
5
Probably on the day of the explosion and the following day: the 25th and 26th of April, 1986.
Big Ideas
1
Radioactivity is carried in many ways across a wide area. This includes through the atmosphere by
winds and through rivers. These do not stop at national borders and so the radioactivity was
carried into other European countries.
2
a This is an oil spill from a shipping accident.
b This is likely to be an accident.
c Oil may affect marine environments and habitats and also coastal environments. This has an
impact on the plants, animals and human activities in the region. Some of these impacts include
oil on sea birds and marine mammals such as seals and otters.
3
Because the wind on the day of the accident was an easterly wind which carried much of the
radioactive material into Belarus, which lies west of the reactor.
4
Answers will vary but some of the key similarities will be the impacts on both land and water and
the long term nature of these impacts.
5
a
High levels
Medium levels
Low levels
Russia
Sweden
Croatia
Belarus
Norway
Estonia
Ukraine
Moldova
Latvia
Austria
Romania
Lithuania
Finland
Slovakia
Poland
Slovenia
Hungary
Czech Republic
Switzerland
Germany
Denmark
Italy
Netherlands
Belgium
France
United Kingdom
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b Countries immediately west of the accident site were most at risk from the nuclear fallout. This
was due to wind direction at the time of the explosion. Countries further way and the northwest
(such as Finland, Sweden and Norway) and to the southwest (such as Austria and Slovenia)
received higher than expected levels of radiation. This may be due to a combination of factors,
such as wind direction, presence of high mountain ranges in these countries and the weight of
the radioactive material.
6
Yes, it could lead to tensions and it did. This was largely due to the Russian authorities deciding
not to inform their neighbours of the accident, giving them no opportunity to prepare their citizens
for the arrival of the radioactive material.
7
Saudi Arabia’s coastline was affected by the oil spill, and the smoke plume from the oil well fires
spread across the country. Iran seems not have been affected by either of these environmental
problems. This may be due to geographic factors, such as the prevailing wind direction that
appears to have carried the smoke in a south-easterly direction over Saudi Arabia, and by ocean
currents that carried the oil spill south.
8
Visual answer. Remember BOLTSS.
9
This depends on your definition of the word ‘worst’. If this means the greatest loss of life then the
deliberate flooding of the Huang He River is easily the worst, with more than 500 000 deaths. If the
definition of ‘worst’ refers to the area affected or the time scale of the effects, then the Chernobyl
disaster is the worst.
10
This question refers back to question 2 on page 184. Answers will vary.
11
Answers will vary and may refer to the old adage that ‘all’s fair in love and war’.
12
Answers will vary but should rely on some background information about nuclear power beyond
that supplied in the chapter. Refer to the teaching plan for suggestions.
Transferring Ideas—The Aeta People: How do we sustain communities in
the face of disaster?
6.1
What impact do tectonic disasters have?
1
Regions on the sides of volcanoes often have rich volcanic soil suitable for agriculture and higher
rainfall than the surrounding lowlands. Floodplains have deep fertile soil and a plentiful supply of
fresh water.
2
Many were killed and about 200 000 were made homeless. Many villages were totally destroyed
and the landscape was covered by a pyroclastic flow meaning that the Aeta may never return to
the region.
3
A pyroclastic flow is a superheated torrent of mud, ash and water that sweeps down the side of a
volcano during an eruption. It is so dangerous because of the great speeds that it reaches as it
flows down the side of the volcano.
4
Perhaps they lived far enough away from the volcano that they were not in immediate danger.
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6.2 How do weather disasters affect communities?
1
Buildings and communities were destroyed and more people were killed.
2
The mudslide in Venezuela in 1999 was similar to a lahar. Human activities such as forest clearing,
road building, and housing construction on slopes all contributed to this disaster.
3
The Philippines is likely to receive typhoons because the country is located in one of the most
typhoon-prone areas in the world. High winds and flooding are often associated with this type of
disaster.
6.3 What problems do man-made disasters cause?
1
They were a hunting and gathering people whose livelihood depended entirely on the forests in
which they lived.
2
It destroys the environment that they rely on for their food and shelter. It is different from manmade disasters, such as the Gulf War and the Chernobyl accident, in that it is due to changes in
the way that the forest is used by other people.
3
It is similar to other man-made disasters as they all resulted in the destruction of the natural
environment and the resettlement of people. The effects of all of these disasters will be felt for a
long time.
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