Worksheet Part1 TE e

Opportunities Opportunities and risks

Senior Secondary Exploring Geography (Second Edition) Part 1 Lesson worksheets

1

hazard-prone areas?

1.1

Is the earth we live on stable?

A

What are natural hazards?

1

Hazards are events that threaten us or cause loss of property

2

Is it rational to live in

human

life life

and

.

Identify whether the following cases are natural events or natural hazards. a

A tsunami which has caused 1,000 deaths and serious loss of property This is a natural ( event / hazard )..

b

A volcanic eruption on a remote island without any settlement This is a natural ( event / hazard ).

c

An earthquake which leads to the damage of a road This is a natural ( event / hazard ).

B

Is the earth we live on stable?

3

Tsunamis, volcanic eruptions and earthquakes are caused by earth

movement

. This

results in violent movements of the earth ’s surface. 4

They are classified as

© Oxford University Press (China) Ltd 2014

tectonic tectonic

hazards.

1


Why is our earth unstable?

1.2 A

What is the structure of the earth?

1

Figure 1 shows the structure of the earth based on chemical composition. Complete Table 1.

F igure 1 Table Tabl e 1

Layer Crust

Thickness

6 – 8 km

Characteristic Characteristic A

Oceanic



It is found under the oceans. It is thin and dense



It consists of mainly iron

25 – 70 70 km

crust / sima

B 

silica

with relatively more

and magnesium

Continental

crust /sial

It makes up the continents and the continental shelves. It is thick and light



It consists of mainly aluminium

2,900 km

C

Mantle 3,470 km

D

Core


silica


, potassium and sodium



It lies below the crust



It is rich in



It is the hottest and densest part of the earth



It is rich in

iron iron

iron iron

and

and

magnesium

nickel

2


Why is our earth unstable?

1.2 A

What is the structure of the earth?

1

Figure 1 shows the structure of the earth based on chemical composition. Complete Table 1.

F igure 1 Table Tabl e 1

Layer Crust

Thickness

6 – 8 km

Characteristic Characteristic A

Oceanic



It is found under the oceans. It is thin and dense



It consists of mainly iron

25 – 70 70 km

crust / sima

B 

silica


and magnesium

Continental

crust /sial

It makes up the continents and the continental shelves. It is thick and light



It consists of mainly aluminium

2,900 km

C

Mantle 3,470 km

D

Core


silica


, potassium and sodium



It lies below the crust



It is rich in



It is the hottest and densest part of the earth



It is rich in

iron iron

iron iron

and

and

magnesium

nickel

2


2

Figure 2 shows the structure of the earth based on the state of material.

F igure 2

a

What are the states of materials in the following layers? Tick () the appropriate column in Table 2. Tabl e 2

Layer Crust Mantle

State

Solid

Oceanic crust and continental crust



Uppermost part of the mantle



Liquid

Lithosphere 

Asthenosphere 

Lower mantle Core



Outer core 

Inner core

b

Plastic

Which two layers in Table 2 above are collectively called the lithosphere? The crust and the uppermost part of the mantle are collectively called the lithosphere.

B

What are plates?

3

a

What are plates? Plates are the broken pieces of the tectonic

b

lithosphere

. They are also called

plates.

What are the characteristics of plates? 1

Shape:

They vary in shape

2

Thickness and sizes:

They have different thickness and sizes

3

The direction of movement:

They move in different directions

4

The kind of crust they carry:

Some carry both oceanic and continental crust; some carry oceanic crust only


3


C

Why do plates move?

4

Research shows that ridge push and slab pull are two major mechanisms which drive plate movement. Fill in the blanks on pp. 4 – 5with the keywords given to show the processes. Some words can be used more than once. magma gravity a

crustal materials asthenosphere

fissure

suction

ridge

sinks

oceanic

density

slab pull

increases

ridge push

Ridge push The intense heat in the earth’s core causes som e

rocks to melt. This molten rock is called (i)

magma

. It rises towards the

surface at some places. a •

When the rising (ii)

magma

reaches the lithosphere, it creates a (iii) b

•

fissure

The upwelling (iv) fill the (v) (vi)

•

there. magma

fissure

will

and form new

crustal

materials

.

These materials are very hot and have a low (vii)

density

. They rise above the

existing crust and form an upswelling (viii) •

ridge

.

These materials gradually cool off, solidify and become a new part of the (ix)

c

•

oceanic

lithosphere.

As this new lithosphere cools, its density (x)

increases

and slides down

from the two sides of the ridge under the force of (xi) •

F igur e 3


•

.

This pushes the rest of the plates away from the (xii)

d

gravity

ridge

This is called (xiii)

. ridge

push

. 4


b

Slab pull •

As the newly formed part of the oceanic lithosphere continues to move away from the ridge, it merges with some of the rock materials in the (xiv)

a

asthenosphere

,

and gets thicker in the process. •

After many millions of years, they become a dense, heavy slab of plate.

•

When this dense slab of plate collides with another plate, it (xv)

sinks

into

the asthenosphere because it is heavier. •

b

This creates a (xvi)

suction

force

that pulls the rest of the plate behind it.

F igur e 4 •

This is called (xvii)

slab

D

What types of plate boundaries are there?

5

a

Draw arrows on Figures 5a to c to show the directions of plate movement.

b

Complete Table 4 about plate boundaries.

pull

.

Table 4

F igur e 5a

Movement of plates Effect on the lithosphere

Type of plate

F igur e 5b

F igur e 5c

Plates diverge or move

Plates converge or move

Plate slide horizontally

apart

towards each other

past each other

New crustal material is formed Divergent plate boundary

boundary


The denser plate sinks into the asthenosphere or subducts

No crustal material is formed or subducts

Convergent plate

Transform plate

boundary

boundary

5


6

Figure 6 shows the distribution of major plates.

F igure 6

a

Name plates A to F in Table 5.

Table 5

Plate

Name

Plate

Name

A

Eurasian Plate

D

Pacific Plate

B

Philippine Plate

E

North American Plate

C

Indo-Australian Plate

F

Nazca Plate

b

Complete the key in Figure 6 to show the distribution of plate boundaries.

c

Draw arrows in the boxes in Figure 6 to show the direction of major plate movement.


6


What are the landforms/features resulted from the major internal forces and processes?

1.3 A

What are the internal forces and processes?

1

a

Identify the internal forces shown by the diagrams in Table 1. Tabl e 1

Original rock

Internal force applies to rock

Type of internal force

Compression

Tension

Shearing force

b

These forces give rise to three internal processes. They are and

volcanism

folding

,

faulting

.

B

What is folding?

2

Study Figures 1a and b. What is folding? Folding is the process by which rock layers are

folded

up

compressional

force.

under

F igure 1a

F igure 1b


7


3

a

Figures 2a and b show the landforms/features formed by folding. Identify them.

Credit: Sadikgulec/Dreamstime.com

Credit: Fotomorgana/Dreamstime.com

F igure 2a

F igure 2b

Fold b

Fold mountain

Give two examples of the landform as shown in Figure 2b. The Himalayas/The Alps/The Rockies/The Andes/The Atlas Mountains (any 2)

C 4

What is faulting? a

i

Compressional, tensional and shearing forces place stress on rock. When the stress exceeds the internal strength of the rock, the rock may ( break apart / fold up ).

ii

What happen when rocks are broken up? When rocks are broken up, they are

displaced

relative to each other.

Faulting occurs. The cracks or fractures along which rocks are displaced are called faults

.

F igur e 3

b

Study Figures 4a to c on p. 9. i

Mark the faults on the right diagram of Figures 4a to c.

ii

Complete the last column to: •

describe the movement of rock blocks; and

•

identify the types of fault shown in the diagrams.


8


Before

After

Description

The rock block on the right ( moves up / moves down / slides past each other). The fault formed is called a normal

fault

F igure 4a

The rock block on the right ( moves up / moves down / slides past each other). The fault formed is called a reverse

fault

F igure 4b

The rock block on the right ( moves up / moves down / slides past each other). The fault formed is called a strike-slip

fault

F igure 4c

5

Faulting may form large-scale landforms called block mountains or rift valleys. Both of them can be formed by both compressional and tensional forces. Refer to Figures 5 and 6 on p. 10. a

State the type of force applied to the blocks in the last column.

b

For each diagram,

c

i

draw the position of the central block after the displacement of rock blocks;

ii

label the movement of blocks with arrows; and

iii

describe the movement of the block(s) in the last column.

Label the resulting landform as shown by the central block.


9


a

Compressional force

biii

The central block (upthrown block) is squeezed up or uplifted

F igure 5a

a

Tensional force

biii

The side blocks (downthrown blocks) sink and the central block (upthrown block) is left

F igure 5b

as it is a

Tensional force

biii

The central block (downthrown block) sinks

F igure 6a

a

Compressional force

biii

The side blocks (upthrown blocks) are pushed up and a depression forms

F igure 6b

d

Name ONE example for each landform. Block mountain: Black Forest/Vosges (any 1); rift valley: Rhine Rift Valley/East African Rift (any 1)


10


D

What is volcanism?

6

a

Volcanism refers to all the processes related to the occurrence and movement of magma:

F igure 7

Y Magma escapes from the

X Magma becomes

The process is called extrusive

lava

magma chamber and

volcanism

reache s the earth’s surface

The process is called

Z Magma cools and solidifies

intrusive

before it reaches the earth’s surface

volcanism F igure 8

b

Refer to Figure 7. Put the answers to the following questions in Table 2. i

Name landforms/features A to H.

ii

Describe the appearance of these landforms/features.

Tabl e 2

A

Volcano

Appears as a

cone

symmetrical

, with a vertical vent at the centre, and

slopes for sides. There is a

crater

at the top of a volcano B

Crater lake

It is formed when the crater is filled with water

C

Lava flow

Lava flows in a sheet form

D

Lava plateau

Sheets of lava pile up

E

Laccolith

Dome-shaped

F

Dyke

Vertical

G

Sill

Sheet-like

H

Batholith

feature found parallel to the bedding plane or tilted sheet-like feature feature found parallel to the rock layers

Large mass of intrusive rock formed deep


underground

11


7

Figure 9 shows a contour map of a volcano. a

Draw a cross-section along line A – B in Figure 10.

b

Mark the volcano and its crater in the cross-section. Label two characteristics of the volcano.

c

Is it possible to have a crater lake in this area? If yes, where will the lake be? Mark the location on the cross-section.

d

Describe the volcano and its related features shown in the cross-section in Figure 10. The volcano is in conical shape. It is high, over 2,000 metres. Its slopes are gentle and symmetrical. A crater lake may develop in the crater if rainwater accumulates in the depression.

F igure 9

F igure 10


12


What are the major landforms found at the plate boundaries?

1.4 A

What are the major landforms/features found at divergent plate boundaries?

1

Refer to Figure 1. Name the four major zones of divergent plate boundary.

F igure 1

2

1

Mid-Atlantic zone

3

Antarctic zone

2

Mid-Indian zone

4

South-east Pacific zone

a

Complete the following flow chart about the landforms found at divergent plate boundaries.

* Tick () the correct answer

Plates

move apart/split

at divergent plate boundaries *

Tensional force leads to two internal processes: folding



faulting

Mid-oceanic ridge



volcanism

Rift valleys


Landforms/features produced

Transform faults

Submarine

volcanoes

and volcanic islands

13


3

Study Figure 2 which shows the Mid-Atlantic Ridge. a

Mark the Mid-Atlantic Ridge in Figure 2.

b

Draw a pair of arrows in Figure 2 to show the movement of the South American Plate and the African Plate.

F igure 2

c

How is the mid-oceanic ridge formed here?

i

Along the

divergent

plate boundaries

at the Atlantic Ocean, the South American Plate and the African Plate

split from each other/

move apart A

ii

Hot

.

fissure

is created.

magma

rises through the

lithosphere and fills the lava cools and new

solidifies

crustal

and have a low

fissure

. The hot

. This creates

materials, which are hot density

. They rise

above the existing crust and form a

ridge

on the seabed. d

How does a rift valley formed at the Mid-Atlantic Ridge? Under tensional force, normal faults occur. As plates continue to move apart, the central block of the ridge sinks to form a rift valley.


14


4

Refer to Figure 2 (p. 14) and Figure 3 below.

F igure 3

a

Is the Mid-Atlantic Ridge shown in Figure 2 a smooth continuous line? Tick the correct answer. Yes, it is a smooth continuous line. 

b

No, it is not. It is broken into short segments.

Refer to sections I and II in Figure 3. What is in between these sections? A fault is in between these sections.

c

Do sections I and II move in the same direction? Yes, they do.

d

Study the section between A and B. Describe the direction of plate movement at both sides. The movement of plates at both sides is in opposite directions.

e

Name the fault found between A and B. A transform fault

5

Figures 4a and b show the formation of submarine volcanoes and volcanic islands at a divergent plate boundary. Fill in the blanks on p. 16 for their formation.

F igur e 4a


F igur e 4b

15


a

Submarine volcanoes i Cracks form in the

ii

plates under

volcanism

force b



Active submarine volcanoes form

occurs

Volcanic islands i

Repeated

eruptions

ii

When they



raise the height of the submarine

rise above sea level , volcanic islands

volcanoes 6

iii

through these cracks,



tensional

When magma rises

are formed

Look at Figure 5 which shows some submarine volcanoes and a volcanic island at a divergent plate boundary. a

Do the submarine volcanoes and volcanic islands stay where they are? No, they will move away from the mid-oceanic ridge.

b

What are the reasons? 

As plates continue to diverge, ridge and slab

pull

be dragged in 

push

will cause the plates to opposite

F igur e 5

directions.

Old submarine volcanoes and volcanic islands are carried away from the zone of rising magma.

B

What are the major landforms/features at convergent plate boundaries?

7

What internal force is produced at convergent plate boundaries? At convergent plate boundaries, plates move Compressional

8

towards

each other or collide.

force is produced.

What happens when two plates collide? When two plates collide, the denser or heavier plate This is called volcanism

subduction

. During collision,

slides/subducts folding

below the other plate. , faulting and

may occur.


16


9

Figure 6 shows the two major belts of convergent plate boundary. In Table 1, a

name belts A and B;

b

describe their distribution.

F igure 6 Table 1

A:

Alpine-Himalayan

belt

It stretches from the

Mediterranean

Sea, crosses the north of India and turns south-east into the B: 10

Circum-Pacific

belt

Indian

Ocean

It nearly surrounds the

Pacific

Ocean

The types of landforms that result from the collision depend on the nature of the crust carried by the plates where they collide. Name the three types of collision below. 1

Ocean-continent collision

2

Ocean-ocean collision

3

Continent-continent collision


17


11

Answer the following questions which are about ocean-continent collision. a

Refer to Figure 7. i

Fill in Table 2. Table 2

Plate X

Plate Y

Nature of

Continental crust

Oceanic crust

crust at the edge

ii

Draw a pair of arrows to show the moving direction of plates X and Y.

iii

Name the belt where ocean-continent collision occurs. The eastern Circum-Pacific Belt

F igur e 7

b

Figures 8a and b shows the process of collision of plates X and Y. Fill in the blanks to describe the process and the resulting landforms.

F igur e 8a

Formation process How do plates move?

The

Nazca

the edge) collides with the (Plate Y) (with

How is sedimentary rock formed?

Plate (Plate X) (with

Sediment from the

South

continental South

washed down and deposited in the Later, the layers of sediment are

oceanic

crust at

American

Plate

crust at the edge). American coastal compacted

landmass is water

.

into sedimentary

rock.


18


F igur e 8b Formation process The three kinds of landforms formed: Landform 1 Landform 2

When denser plate subducts, an (

Peru-Chile

and elongated

trench

Trench) is formed at the plate margin. It is a deep trough

under the sea.

Because of the collision of plates, sedimentary rock is Fold

Landform 3

ocean

mountains

(

folded up

The Andes

.

), are formed.

During subduction, water released from the subducted plate causes the asthenosphere

to melt at a lower temperature. This forms magma.

Folding and subduction result in

compressional

force, this

produces cracks in the rock. When magma rises through cracks, volcanic eruption occurs. This forms volcanoes c

, for example,

Mount Chimborazo

.

Draw an annotated diagram in the space provided below to show the landforms created by ocean-continent collision at the convergent plate boundary. (Hint: collision of plates; direction of plate movement; subduction of denser plate; presence of ocean trench, fold mountain and volcanoes)


19


12 Ocean-ocean collision occurs when two plates carrying oceanic crust at their edges collide. Refer to Figures 9 and 10 about ocean-ocean collision between the Eurasian Plate and the Indo-Australian Plate. Fill in the blanks about the formation of two major landforms/features.

F igure 9

a

Ocean trenches

i

How do plates move here?

The

Eurasian

Plate collides with the Indo-Australian Plate.

F igur e 10a

ii

How is this ocean trench formed? What is the name of this ocean trench?

The denser

Indo-Australian

This produces an b

Volcanic island arcs

i

How do plates move

Plate subducts under the

ocean

trench

called

Eurasian Java

Plate.

Trench

.

here?

The

Eurasian

Plate collides with the Indo-Australian Plate.

F igur e 10b


20


ii

How is the volcanic island arc formed?

The denser

Indo-

Australian Plate subducts under the Eurasian

Plate.

During subduction, magma is formed and cracks are produced. Magma then rises up F igur e 10c

through the cracks. This results in

volcanic

volcanoes appear

eruptions

parallel to

on the sea floor. A chain of submarine

the ocean trench. After repeated eruption,

some submarine volcanoes may rise above sea level to become volcanic islands . They finally develop into a chain of volcanic island called a volcanic iii

island

arc

.

Give some examples of volcanic islands along this volcanic island arc.

Sumatra, Java and Bali

are some of the volcanic islands along the

island arc that makes up the country of Indonesia. c

Draw an annotated diagram in the space provided below to show the landforms created by ocean-ocean collision at the convergent plate boundary. (Hint: collision of plates; direction of plate movement; subduction of denser plate; presence of ocean trench, volcanic islands and volcanic island arc)


21


13

Refer to Figure 11 which shows the continent-continent collision at Plate boundary A. a

On Figure 11, i

label plates X and Y.

ii

draw some arrows to show the direction of movement of plates X and Y.

iii

color the convergent plate boundaries in RED.

iv

name and label the fold mountains found at Plate boundary A.

F igur e 11

b

Refer to Figures 12a and b. Complete the paragraphs below to show the situation before the formation of the fold mountains. •

Million years ago, the and the

Asian

by an ocean.

Indian

continent were separated

Plate

Indo-Australian towards the

subcontinent

Eurasian

movement caused the Plate to move Plate.

F igur e 12a

F igur e 12b •

The collision caused the subduction of the ocean floor at the contact zone (

•

oceanic

crust) to be under the Asian continent.

Landforms associated with an ocean-continent collision such as (1) trench


and (2)

volcanoes

ocean

were formed.

22


c

Refer to Figures 13a and b. Follow the guiding questions to write paragraphs to show the formation of the fold mountains.

F igur e 13a F igur e 13b

Guiding questions Where did sediment come from? Where did it deposit?

Formation process

Before both continents met, sediment from each of them was washed down and deposited in the coastal waters around them.

How was sedimentary rock formed?

Due to the weight of the overlying sediment, water was squeezed out. The layers of sediment were compacted into s edimentary rock.

What happened when the two landmasses got closer?

As two landmasses got closer, the ocean floor between them eventually subducted. The Indian subcontinent directly collided

What happened to the sedimentary rock?

with the Asian continent. As the continental crust of the two continents was thick and light, neither of the continents could subduct. The sedimentary rock between the two plates experienced great compressional force. Folding occurred and the rock was folded up to form a fold mountain range.

Name the fold mountain formed.


It is called the Himalayas.

23


14

Figure 14 concludes the types of collision and the landforms formed at convergent plate boundaries. Complete the flow chart. Plates converge Convergent

Ocean-continent collision

plate boundaries

Ocean-ocean collision

Continent-continent collision

Resulting landforms:



•

Ocean trenches

•

Ocean trenches

•

•

Fold mountains

•

Volcanic island arcs

•

Volcanoes

Fold mountains

F igure 14

C

What are the major feature found at transform plate boundaries?

15

What internal force is produced at transform plate boundaries? At transform plate boundaries, plates slide Shearing

16

past

horizontally each other.

force is produced.

What happens when two plates slide past each other? What feature is formed? When two plates slide past each other, ( new / no new ) crustal material is formed and ( the denser / neither ) plate subducts. The internal force produced at these plate boundaries forms transform

17

faults

(feature).

Name the most active and typical example of a transform plate boundary. It is the Plate and the

San Andreas Fault Pacific


. It is found between the

North

American

Plate.

24


How do plate movements create hazards?

1.5 A

How do plate movements create earthquakes?

1

Refer to Figure 1. The boxes i, ii and iii refer to some important terms related to earthquakes.

F igure 1

a

What is an earthquake? It is the

b

sudden

shaking

of the land.

How is it caused? sudden release of energy stored in the rocks beneat h the earth’s

It is caused by the surface •

:

When the stress is applied to rocks, fracture

•

When the

energy

builds up in the rock layer and a

is formed; energy

exceeds the

strength

of the rock, the rock

breaks and displaces along the fracture. c

Fill in the boxes in Figure 1 to show the important terms related to earthquakes.

d

Which place, X, Y or Z, will have the strongest destruction if earthquake occurs in the area? What is the reason? Place X will have the strongest destruction. Compared with places Y and Z, Place X is the closest to the epicentre where most of the energy is released from the focus.


25


2

Figure 2 shows the distribution of earthquakes of the world in a selected month of a year.

F igure 2

a

Describe the distribution of earthquakes with reference to plate boundaries. Earthquakes can be found at

b

all types of plate boundaries

.

Convergent and transform plate boundaries produce more earthquakes. Explain. This is because when plates past

move

each other, friction and

towards stress

are great.

or

slide Energy

builds

up more easily and rapidly at the plate boundaries. c

Some earthquakes are found far away from plate boundaries. i

Give two examples. Hawaiian Islands, eastern USA, central Asia (any two or other reasonable answers)

ii

Suggest reasons. Some earthquakes may be triggered by volcanic eruptions at hot spots. Some earthquakes are generated from fault systems which may affect the nearby plates.


26


3

Figure 3 shows the depth of earthquake foci at different types of plate boundary.

F igure 3

a

Describe the depth of earthquake foci at different plate boundaries. At convergent plate boundaries, shallow to and transform plate boundaries,

b

shallow

deep

earthquakes occur. At divergent

earthquakes occur.

How is the depth of earthquake foci related to plate movement? Subduction

of plates causes friction at a great depth, therefore generating

intermediate- to deep-focus earthquakes.

Non-subduction

plate movements

cause shallow-focus earthquakes.

B

How do plate movements create volcanic eruptions?

4

Figure 4 shows the distribution of active volcanoes in the world.

F igure 4


27


a

Describe the distribution of active volcanoes. Active volcanoes are found at

convergent

and

divergent

plate

boundaries. They form a rough circle around the Pacific Ocean and is known as the Pacific Ring of Fire b

.

Why do volcanic eruptions occur at convergent plate boundaries? At

convergent

The melting of the

plate boundaries, collision of plates builds up asthenosphere

and extend downward to the

creates magma. When

magma

chamber

pressure

cracks , the

.

develop

magma

will then rise through these cracks. c

Some volcanic eruptions have been occurred in scattered places away from plate boundaries. Complete the following paragraphs for the explanation. Away from plate boundaries, there are often lines of volcanic islands. They are located above . A hot spot is where

hot spots

a mantle plume rises

from between the core and the mantle . At a hot spot, magma rises and erupts at the earth’s surface and forms volcanoes, volcanoes or

submarine

volcanic

islands

. F igure 5a

As the plate moves, the volcanoes/ volcanic islands/submarine volcanoes are carried away. The hot spot later creates new volcanoes just above it. The process is repeated and this results in a line of volcanic

islands

.

The further the volcano from the hot spot, the

older

the age of it.

A famous example of volcanoes/ volcanic islands formed by a hot spot is the

Hawaiian Islands


.

F igur e 5b

28


C

How do plate movements create tsunamis?

5

a

What are tsunamis? Tsunamis are

a series of big sea waves that can travel at a speed of 700 kilometres per

hour or more. Once generated, they travel in all directions. . b

Figure 6 shows the three causes of tsunami. With reference to this diagram, explain why tsunamis are most often generated at convergent plate boundaries.

F igure 6

Tsunami is caused when the sudden

vertical

displaces a large body of

. The causes for this situation include submarine

earthquakes landslides

water

, submarine

volcanic eruptions

of rock

and submarine

.

At convergent plate boundaries, plates plate subducts. Friction and stress are great. energy

displacement

exceeds the

strength

collide

and the

denser

Energy

builds up. When the

of the rock, the rock breaks and displaces

along the fracture. If the epicentre is under the sea, submarine

earthquakes

may be

generated. If the displacement is a vertical one, it can displace a large body of water and cause tsunamis. At these plate boundaries, submarine landslides

volcanic

eruptions

and submarine

are common. If either event causes vertical displacement of water,

tsunami is also resulted. c

Why are tsunamis most active in the Pacific Ocean? This is because the plate boundaries in the Pacific Ocean are mainly

convergent ones.

The above three causes occur most frequently at convergent plate boundaries. . © Oxford University Press (China) Ltd 2014

29


1.6

What destruction do tectonic hazards cause? How can we deal with them?

A

What destruction do earthquakes and volcanic eruption cause?

1

Fill in the flow chart in Figure 1 to show the major destruction caused by earthquakes. Earthquakes

Damage structures, such as: •

Buildings/hospitals

•

Bridges

•

Roads/Railways/

of underground gas

Trigger:

pipes and power lines causes fires

Transport facilities •

• Breaking

• Breakdown

communication • Spread

Dams

of

•

landslides

•

avalanches

•

tsunamis

links

diseases

Loss of

life

and

property

F igure 1

2

Fill in the flow chart in Figure 2 to show the major destruction caused by volcanic eruption. Lava

• Burns

houses, crops and vegetation

• Damages

• Loss

communication

of

and • Causes • People

Volcanic

Volcanic ash

eruption

mudflows

after rain

property

• Destruction

may find it difficult to

of

natural

breathe • Blocks

life

environment sunlight

and

lowers visibility • Affects

traffic and damages farmland

• Poisonous

Gases

• Sulphur • High

gas kills people

dioxide can cause

acid rain

concentration of carbon dioxide can kill

people and animals Triggers landslides,


earthquakes

or even tsunamis

F igure 2 30


B

What destruction do tsunamis cause?

3

Read the news clipping in Figure 3 and answer the questions.

South Asian tsunami in 2004 A submarine earthquake of 9.0 on the Richter scale struck the seabed off Sumatra, Indonesia at 07:58 local time on 26 December 2004. The earthquake had triggered a huge tsunami that hit many countries surrounding the Indian Ocean. The tsunami reached a height of 30 metres and caused widespread destruction. It knocked down buildings and houses, swept ships and boats, flooded low-lying areas, drowned thousands of local people and tourists, destroyed coastlines, beaches, fish ponds and vegetation. The earthquake together with the tsunami killed over 280,000 people and caused huge economic los s. F igure 3

a

Figure 4 shows typical destruction caused by tsunamis. Complete the flow chart with reference to the 2004 South Asian tsunami. Ships

and other objects swept ashore

Buildings

collapse, houses smashed

and washed away Tsunami

Flooding drowned

or

washed away; disease may spread

b

eaches

of

life

and

property

• Local

ecosystem

disrupted

People and animals

B

• Loss

washed away

• C

oastline

changes F igure 4

Read the case study of the 2011 Tohoku tsunami in Japan on pp. 65 – 6 of the textbook. Why is the impact of this tsunami so serious? This tsunami not only caused destruction as in the case of the 2004 South Asian tsunami, it also damaged the back-up power generator of a nuclear power plant. This resulted in the meltdown of the three nuclear reactors and the leakage of radioactive materials. Radiation contamination has long-term adverse impact on people.


31


C

What has been done to minimize losses caused by tectonic hazards? How effective are they?

4

Table 1 (pp. 32 – 3) shows the measures of reducing losses caused by tectonic hazards. Complete the table. Table 1

Measures

Details

i

For earthquakes

Monitoring and warning systems

•

Aim: •

Use

seismographs

and

satellites

to monitor earthquakes

to give time for evacuation

For volcanic eruptions

,

•

Use instruments to detect volcanic activities

•

Study the history and

which helps reduce casualties

geological

structure of the volcano For tsunamis •

Use

tsunami

buoys

and

ocean-bottom tsunami gauges to monitor tsunamis •

Set up warning systems and warning centres, such as the

Indian Ocean Tsunami Warning System,

Pacific Tsunami Warning Centre

ii

Hazard-proof structures

For earthquake-prone regions

Aim:

•

•

Erect buildings and structures with

to provide protection and

earthquake-proof

designs, e.g. the one shown on

help prevent the

the right

collapse of structures , thus reducing the numbers of injuries and deaths

For eruption-prone regions •

Build strong and steep-sided roofs to shed the ash

•


Build

barriers

to stop lava flows

32


ii

Hazard-proof structures

For tsunami-prone regions

(con’t)

•

Construct

•

Reinforce coastal structures

•

Provide

sea

walls

vertical

evacuation

routes

for coastal structures iii

Land-use planning

For earthquake-prone regions

General policy:

•

•

areas, such as

Avoid building facilities with potential danger, e.g.

•

nuclear plants, oil

Govern the

height

•

schools

and indoor stadiums

Issue

volcanic hazard-zone maps

for preparing emergency evacuation plans

buildings Establish

Designate

For volcanic regions

and structures of

•

parks

as shelter centres

depots •

Reserve large open spaces as safety evacuation

evacuation

For tsunami-prone regions •

routes

Encourage people to move from coastal area to higher ground

•

Design a coastal belt for beaches or woodland reserves

•

Build

evacuation

routes leading to

higher ground iv

Education and drills

•

Aim: •

Example:

regular large-scale earthquake

drills

to raise the awareness

of

people about tectonic hazards v

Rescue systems

•

well-equipped

Aim: •

to reduce the number of

teams are well-trained and

Rescue

•

Use advanced equipment such as advanced life detectors, helicopters, medicines and wireless

deaths

communication networks vi

Other measures


•

Provide

disaster

•

Provide

insurance

aid against hazards

33


5

Read the news clipping in Figure 5 and answer the questions.

Strong earthquake triggered tsunami in the Mentawai Islands in Indonesia An earthquake of 7.7 on the Richter scale occurred off the western coast of Sumatra, Indonesia on 25 October 2010. The earthquake had triggered a localized tsunami that struck the Mentawai Islands. The tsunami reached a height of 3 metres and swept as far as 600 metres inland of the islands. It caused widespread destruction and killed 435 people. The bad weather, the rough sea and the remoteness of the islands had caused the delay of relief. Indonesian military and international aid organizations could only reach the islands two days after the ts unami. Although a tsunami warning was issued after the tsunami, people on these remote islands do not have radio access. They therefore did not receive warnings. F igure 5

a

How effective are the following measures in the Mentawai Islands in Indonesia? i

Monitoring and warning systems - it is not effective - people have no access to radios and therefore they did not receive warnings

ii

Rescue systems - it is not effective - rescue had been delayed by bad weather and rough sea

b

Would you suggest building hazard-proof structures on the Mentawai Islands? Why or why not? Open answer. Suggested answer: Yes, because it offers more protection to local people. No, because Indonesia has limited capital and technology. Corruption makes building laws difficult to be enforced. Providing more education and drills may be more helpful.


34


D

What factors cause a place to be more vulnerable to tectonic hazards?

6

There are many factors affecting the level of destruction. a

Complete Table 2 which shows the factors concerning the affected area. Table 2

Factors concerning the affected area

Less vulnerable to

tectonic hazards

tectonic hazards

i

Population density of the area

(Higher/Lower)

(Higher/Lower)

ii

Level of economic development

(Higher/Lower)

(Higher/Lower)

iii

Preparedness of people

Less prepared

More prepared

iv

The weather after the hazard

Extreme weather condition

Normal weather condition

occurs

v

vi

b

More vulnerable to

Relief of land: •

For earthquakes:

steep slopes

gentle slopes

•

For volcanic eruptions:

steep slopes

gentle slopes

•

For tsunamis:

low-lying areas

higher ground

narrow inlets of

wide inlets, deep

shallow water

water

Coastal relief (for tsunamis)

Complete Table 3 which shows the factors concerning the tectonic hazards. Table 3

Factors concerning the tectonic

More serious

Less serious

hazards

destruction

destruction

i

Magnitude of earthquakes

Higher

Lower

ii

Duration

Longer

Shorter

iii

Onset speed

Fast (occur suddenly)

Slow

iv

Distance from the sources

Short distance from/ Closer to the source

Long distance/Farther away from the source

the hazard ‘travels’

Directly hit by the hazard

Not directly hit by the hazard

Time of the occurrence

Night-time, rush hour

Off-peak hour

of destruction

v

vi

The path through which


35


E

What makes less developed countries suffer more than more developed countries?

7

Refer to pp. 77 – 8 of the textbook for the case studies of earthquakes in Haiti and New Zealand. Complete Table 4 below to compare the backgrounds of and losses caused by the two earthquakes. Tabl e 4

Port-au-Prince, Haiti

Canterbury Plains, New Zealand

Magnitude of earthquake (Richter scale)

7.0

7.1

Depth of focus of earthquake

13 km

10 km

Time of occurrence

16:53

04:35

Number of deaths

316,000

0

Number of injured

300,000

102

Buildings destroyed

90% of the buildings in the city were destroyed

A few old buildings were damaged

Infrastructure affected

All hospitals, transport facilities Power cut, water and sewage and communication systems pipes broken, roads cracked and damaged or destroyed; public bridges collapsed telephone system not functional; fibre-optic connectivity disrupted

Level of economic development

Low

High

Level of technology

Low

High

Level of education

Low

High

Population density

High

Low


36


8

From the case study of Haiti and Figure 5 (p. 34) about the tsunami in Mentawai Islands, can you generalize the reasons for less developed countries to suffer more in tectonic hazard? Fill in the blanks in Figure 6. Lack of

capital

Poorly

and technology High

developed

transport network urban

Low

population density

Non-hazard-proof/Poor building material

awareness

of people

Inefficient

and

corrupt government

F igure 6 EXTENDED

9

Refer to textbook p. 83. What can less developed countries do with limited resources? Complete Table 5. Tabl e 5

Measures

a

Increase people’s awareness of hazards

b Land-use planning

c

Cooperate with

i

Education

ii

Propaganda

i

Building hazard-proof structures/buildings

ii

Reserve open spaces

i

Economic:

other countries

the economy

or international organizations

Attract foreign investment to improve

ii

Technology:

Invite specialists from technology-advanced countries to share knowledge and give advice

iii

Research:

Join international research bodies which study hazards

iv

Forecasting and warning systems:


Send officers overseas to learn about forecasting and warning systems

37


Is it rational to choose to live in hazard-prone areas?

1.7 A

What is a rational decision?

1

When deciding to leave or stay in hazard-prone areas, a rational person will weigh possible gains and losses. What does a rational person concern? Complete Figure 1. Possible gains: More

safety

Possible losses: for one’s life and

Losses in the new

property

economic

social

and

environment

Move away?

Staying behind?

Possible gains: Opportunities offered by

Possible losses: resources

available in the hazard-prone area

Probability of hazard reoccurrence and the anticipated

destruction

F igur e 1

B

What do people consider when deciding to leave or stay in hazard-prone areas?

2

What do people consider when deciding to leave or stay in hazard-prone areas? a

Risks

The more risks people perceive, the

less

likely they choose to stay.

The perceptions of people depend on: - education level

- religious background

- past experience

- the character of the person


38

Worksheet Part1 TE e

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