Topical Notes · 2018-09-06 · Convectional currents in mantle result in convergent plate movement...

2012

[CORE PHYSICAL GEOGRAPHY]

Topical Notes

Lim Ting Jie

VS Class of 2011

TOPIC 1: PLATE TECTONICS AND RESULTING LANDFORMS

What is the Plate Tectonics Theory?

Tectonic plates are pieces of the Earth that make up the surface of the Earth and are in constant

motion.

It describes the Earth as restless and suggests that the Earth’s crust is made up of 7 major

crustal plates.

Why do the plates move?

1. There are convection currents in the mantle which drag the plates above them.

2. Magma in the mantle is intensely heated, expands and rises. The rising magma spreads out below

the plates, cools and sinks.

3. The continuous heating and cooling of the magma set up convection currents in the mantle.

What are the differences between continental plates and oceanic plates?

CONTINENTAL PLATES OCEANIC PLATES

1. carry the continents 1. lie beneath the oceans

2. mainly made up of continental crust with oceanic crust lying beneath it

2. mainly made up of oceanic crust

3. consists mainly of granitic rocks (lighter in

colour, less dense)

3. consists mainly of basaltic rocks (darker in

colour, denser)

4. rich in sial (compounds of silicon and

aluminum)

4. rich in sima (compounds of silicon an

magnesium)

5. discontinuous, forming the continents 5. continuous, forming the ocean floors and

bases of continents

6. Examples:

Eurasian

African

North American

South American

Indo-Australian

Antarctic

6. Examples:

Pacific

Nazca

Philippine

Caribbean

Cocos

Scotia

Oceanic-oceanic divergent plate movement (South American and African plate Mid-Atlantic ridge)

9+1

C

Convectional currents in mantle result in tensional divergent plate movement

Cause the African plate to be pulled apart from the South American plate

F

B

Fractures and cracks appear

Basaltic magma flows out from the mantle

Spreads outwards along the fractures

S Magma solidifies and forms new crust or new sea floor at the constructive boundaries

S Causes old crust to be pushed away from plate boundary by sea-floor spreading

P

M

More basaltic magma piles up and solidifies forms a chain of mountains known as mid-

oceanic ridges on either side of the spreading zone

D Youngest mountains are the closest to the spreading zone while the oldest are the

furthest away from it (distancing)

V Mid-Atlantic ridge, part of it rises above the sea to form a chain of volcanic islands (i.e.

Iceland)

O Rift valleys, submarine rift volcanoes and earthquakes also form (others)

Continental-continental divergent plate movement (African and Arabian plate East African Rift Valley)

6+1

C


Cause the African plate to be pulled apart in opposite directions along the eastern and

western rifts from the Arabian plate

Plates are pushed upward as well

F

Both plates are continental

Hence cracks to appear known as normal faults with further tensional forces

Faulting

B

Further application of pressure

More tension is generated

African plate starts breaking into several blocks like the Somalia block, Nubian block and

Tanzania block

M

V

Further application of pressure generates more tension

Central block of rocks start moving up along the fault lines to form block mountains

Some parts slip down along the fault lines to form rift valleys

L The rift valleys get filled with water over time

Form lakes like Lake Victoria and seas like the Red Sea

R Upwelling of magma along the fault line which escapes onto the Earth’s surface

Builds up into rift volcanoes like Mount Kilimanjaro and Mount Kenya

*How is the appearance of the East African Rift Valley described?

1. Apperance: Stepped appearance presence of multiple fault lines cause blocks to be

displaced in relations to each other

2. Mountains: Blocked mountains formed as raised blocks on either side on the rift valley

3. Escarpments: where faults have developed and the centre block subsided

4. Lakes: where water accumulates within the valley or depression

5. Volcanoes: where magma escapes through cracks or faults and solidifies

Continental-continental convergent plate movement (Indo-Australian and Eurasian plate Himalayas)

T Large area of sedimentary layers in the Tethys Sea once separated Asia and India

7+2

C

Convectional currents in mantle result in convergent plate movement

Cause the two land masses surrounding the Tethys Sea, Eurasian plate and Indo-

Australian plate, to converge

L Oceanic lithosphere subducts beneath the Eurasian plate

N

Both plates made of relatively light and buoyant rocks with equal thicknesses and have

similar densities

There is no subduction between the two plates

C

B

S

A

Rock strata along the boundary are compressed

Continental sedimentary rock layers between the plates are forced to buckle and fold

Sediments are scraped off from the edges of the Indo-Australian plate

Build up and accumulate to form the continental fold mountains Himalayas

G Indian landmass still pushing into Eurasian plate

Himalayan mountains still growing skyward about 5 cm per year

What are the differences between faulting and folding?

FAULTING [C-C=D] FOLDING [C-C=C]

1. rocks are displaced relative to each other to

cause breaks or fractures in rocks

1. rock strata along the boundary are

compressed to cause the strata to buckle and fold

2. caused by stresses and strains in rocks of two

plates as they move in response to convection currents

2. caused by the bending of the Earth’s crust

under the pressure of compression

3. frequent in areas with brittle rocks (igneous

and metamorphic rocks)

3. frequent in areas with sedimentary rocks

4. stores up stress and suddenly releases it,

causing earthquakes

4. gradually releases stress

Oceanic-continental convergent plate movement (South American and Nazca plate Andes)

8+1

C


Cause the Pacific plate to be brought towards the Philippine plate


D

S

The oceanic Nazca plate, being thinner and denser

Subducts under the thicker, less dense continental South American plate

D

T

Dipping of oceanic plate into the mantle

Forms a long, deep and narrow trench Peru-Chile of about 8000 m deep

F

Continental South American plate rides over Nazca plate

Part of the ocean floor is scraped of

Edges and sediments near the edges and on the ocean floor are folded and crumpled

S Thick layers of squeezed sediments rise to form the fold mountains Andes

S Edges of Nazca plate melt as it gets pushed into the mantle

Forms silica rich magma at destructive boundaries

V

Magma formed by melted oceanic crust erupt

Rises to Earth’s surface through fractures

Forms subduction volcanoes Nevado del Ruiz and the Cotopasi volcano

Oceanic-oceanic convergent plate movement (Pacific and Philippine plate Mariana islands)

8+1

C


Cause the Pacific plate to be brought close to the Philippine plate


D

S

The Pacific plate, being furthest away from sea-floor spreading and hence denser

Both plates are continental

Pacific plate subducts under the less dense Philippine Both plates

D

T

Dipping of Pacific plate into the mantle

Forms a long, deep and narrow trench Mariana Trench of about 11 thousand metres deep

F

Both plates are about the same density as both are very dense

No blucking occurs

No fold mountains are present

S Edges of Pacific plate melt as it subducts under the Philippine plate

Forms silica rich magma at destructive boundaries

U

Magma formed by melted oceanic crust erupt

Rises to Earth’s surface through fractures

Forms undersea submarine volcanoes

V Volcanoes build up and appear above the sea to form volcanic islands

Transform plate movement (Pacific and North American plate San Andreas Fault)

1. Both plates slide past each other lateral movement occurs

2. There is little volcanic activity and crustal material is neither created or destroyed along the

conservative plate boundary

3. Plates grind against each other as they move in opposite directions tear faults form cause

earthquakes due to the great amount of stress built up

How are the landforms formed by faulting and folding different?

PROCESS RESULTANT CONSEQUENCES EFFECT

Types of

folds

Symmetrical

fold

Both limbs are of equal steepness Compression from opposite

sides is equal

Asymmetrical

fold

One limb is steeper than the other Compression is greater from

one side than the other side

Overfold One fold is pushed over the other limb Increasing compression

Recumbent fold Limbs are nearly parallel to each other Increasing compression

Overthurst

fold

One limb is pushed forward and

overrides the other

Fracture occurs along the

fault plane

Types of

faults

Normal fault

Two blocks of rocks are pulled apart,

forming a steep cliff or scarp

Tensional forces cause rocks to

break and fractures to form

Land in between the fault sinks

Two blocks of crust left

standing above the

surrounding land as block

mountains

Graben forms between the

fault

Reverse fault

Two blocks of rocks are compressed,

forming an overhanging escarpment

Compressional forces cause rocks to

break and fractures to form

Two blocks are uplifted to

form block mountains

Graben forms between the

fault

Tear fault Occurs when adjacent blocks slide past each other horizontally

along the fracture

Types of

landforms

Block

mountains

When a block mountain is horizontal, it is called a horst.

However, erosion and weathering may reduce the horst to a range of

rounded hills.

Graben

When the graben is widened, an elongated deep valley with two high

blocks at the sides known as the rift valley is formed.

Lakes and volcanoes may form on the floor of a rift valley. Faults

provide a passage for magma to rise to the surface to form rift

volcanoes

What is the distribution of earthquakes and volcanoes around the world due to plate movements?

1. Earthquakes and volcanoes are found along plate boundaries where they are areas of instability.

2. Constant plate movement where plates converge, diverge or slide past one another give rise to

earthquakes and volcanoes.

3. Other landforms that forms that the zones

Mid-oceanic ridge Rift valley Oceanic trench Fold mountains Volcanoes Earthquakes

O-O=D

C-C=D

O-C=C

O-O=C

C-C=C

Transform Few/none

4. Circum-Pacific Belt / Pacific Ring of Fire

a. Zones of colliding or sliding plates which stretch from New Zealand, South Western

Pacific, Indonesia, Philippines, Japan, past the Aleutian Islands, Alaska in North America,

down the Cascade Range and Andes Mountains on the west coast of South America.

5. Mediterranean-Alpine Belt / Alpine-Himalayas-North India system

a. Zones of colliding plates which stretch from the Himalayas to the Alps and the

Mediterranean region.

6. Belts of minor (earthquake) activities

a. Mid-Atlantic Belt that coincides with the belt of volcanic islands in Atlantic Ocean and is

in the zone of diverging plates beneath an ocean.

b. East African Rift Valley which is in a zone of diverging plates beneath a continent

7. Areas of minor (volcanic) activities

a. Hotspots found away from plate boundaries in the interior of the plates like the Hawaiian

islands and Easter island give rise to volcanoes

Describe the main types of volcanoes and account for the differences in their shapes

COMPOSITE VOLCANO ACID VOLCANO SHIELD VOLCANO

1. Lighter pyroclasts erupts first,

then followed by lava

composed of alternate layers

of pyroclasts (ash and cinder)

and acid lava

1. Composed of layers of

acid lava

1. Composed of layers of basic

lava

2. Viscous (moves slowly and cools

quickly)

forming steep slopes at the top

gentler slopes at the base

2. Viscous (moves slowly

and cools quickly)

forming steep

slopes

2. Fluid (moves quickly than

acid lava and spreads out

far before cooling)

gentle slopes

3. Solidifies in central pipe, building

up pressure, resulting in a violent

eruption

lighter pyroclasts fall around

the vent

the top to be steeper than the

base

3. Solidifies in central

pipe, building up

pressure, resulting in a

violent eruption

steep slopes of acid

lava only

3. Spreads out quickly before

cooling

gentle slopes

broad base

4. More lava and pyroclasts are

added to the volcano

constant elevation of volcano

4. More lava added to

the volcano

constant elevation

of volcano

4. Spreads out quickly,

solidifies usually near base

constant widening of

volcano’s base area

Earthquakes

Danger and direct effects of earthquake Example

Land-

slides

Soil on hill slopes loosen

Large amounts of rocks and soil from a hill slope slide

down.

People and infrastructure like roads and water pipes may

be buried under the soil.

1999 Taiwan Earthquake

caused many vehicles

travelling along were

swept down mountain slopes.

Entire villages were

buried under the massive

landslides.

Fires

Caused by damaged wires, overturned stoves and broken

gas pipes when the ground shakes.

Fires can cause deaths and the collapse of infrastructure,

leaving more people injured and homeless.

Furthermore, water, electricity and gas supplies and

emergency services would be disrupted, delaying the help

given to the affected regions.

1995 Kobe Earthquake in

Japan caused many

wooden houses to catch

fire and leaving the

inhabitants homeless.

Infra-

struc-

ture

col-

lapse

Infrastructure may not be designed to withstand

earthquakes as they are built on weak foundations.

Some earthquakes may not cause immediate collapse on

infrastructure, but may weaken the foundations of

buildings and transport networks.

Repair works has to be carried out; otherwise the

affected infrastructure may collapse within months.

1999 Turkey Earthquake

caused 4000 buildings to

collapse as they were not

built to withstand

earthquakes.

Tsu-

namis

a) Constant movement of 2 (named) tectonic plates due to

convectional currents under the mantle

b) This results in the build-up of pressure and stored energy

due to the unsmooth movement of the plates

c) Stored energy is released when the rocks snap and

fissure causes the sea level to dip temporarily

d) Sudden movements in the sea bed and underwater

vibrations along the plate boundary result in a series of

giant waves.

e) The waves travel at speeds of up to 800km per hour

across the ocean.

f) Increased friction between the waves and shoreline

reduces the speed of the waves, slowing down the waves

to a huge wall of up to 6m before crashing onto land.

2004 December

undersea earthquake

occurred in the Indian

Ocean near Sumatra,

triggering tsunamis.

These waves travelled

thousands of kilometers

before crashing onto the

shores of Indonesia,

Thailand, Sri Lanka and

India.

Impacts and long-term effects of earthquakes Example

Diseases

spreading

Homeless people put in temporary shelters like

schools and tents.

Temporary shelters usually overcrowded and

lack of proper sanitation.

Poisonous materials from broken sewage pipes

can cause diseases like typhoid and cholera.

Haiti earthquake 2010 resulted

in more people dying and falling

ill instead of the earthquake

itself due to the spread of

diseases

Lives lost

Results from fires, collapse of buildings or

tsunamis causing severe injuries and death

Aftershocks delay rescue efforts and endanger

rescuer’s lives

2005 Kashmir Earthquake

destroyed many houses, took

away many supplies and left

many roads buried under rubble

Impacts and long-term effects of earthquakes Example

Economic

impacts

Inconvenience may be caused to the business

area with the destruction of roads, industrial

buildings, water pipes and electrical supplies

Tsunamis by undersea earthquakes can destroy

habitats of marine life, decreasing the amounts

of fish and prawn farmers catch

2004 Indian Ocean Tsunami

caused Phuket to suffer a

drastic drop in the number of

visitors

Trauma

Hard to live with loss of families and friends

Ongoing triggers bring back the trauma like

taking transport or deadly silence

1985 Mexico City Earthquake

caused many civilians to be seen

suffering from uncontrollable

crying and fits of anger even

after a few years since the

earthquake.

Success of preparing for an earthquake

1. Education and Drills

Drills are conducted regularly to educate and familiarise

people on what to do.

In Japan, students have to crouch under the nearest

table when the earthquake signal goes off.

Posters and signs are put up to show evacuation routes so

that people do not panic and can move to safer regions

immediately.

Complacency

The success depends solely on the

people.

If they are complacent and do not

see the importance of earthquake

education, they will be less

prepared when an earthquake

strikes.

2. Planning of location of infrastructure

Local authorities must determine the nature and extent

of earthquake risks in earthquake-prone areas.

They can control land use so that houses or tall buildings

are not built in earthquake prone areas.

Authorities were able to determine the nature of the

earthquake risks in Washington by estimating the level of

expected ground shaking and identifying the sites prone

to ground failures and tsunamis.

Difficult control of land use

However, in developing countries,

it is difficult to control land use

as population growth is fast.

Also, people migrate from rural

areas to cities and build their

homes illegally on earthquake

prone areas without approval

from authorities.

3. Designing new infrastructure

Steel bars are used in the cross-bracing method to

strengthen new infrastructure to be better equipped to

withstand earthquakes

Shock absorbers are used in foundations to help absorb

tremors of the earthquake

Transamerica Pyramid in San Francisco was able to

withstand the Loma Prieta Earthquake of 7.1 on the

Richter scale

Expensive to construct

Transamerica Pyramid in San

Franciso costed S$75 million to

build

Poorer places in the world may

not be able to afford such

technology

4. Earthquake monitoring and warning system

Factors influencing earthquake extent

[1] Magnitude

The strength of the force the earthquake releases. 3 on the Richter scale usually cannot be felt.

8 causes total destruction, destroying even concrete structures.

[2] Distance

from

epicentre

Places near the epicentre (i.e. point on the Earth’s surface that is directly above the focus of an earthquake) generally receive the strongest shock waves due to shorter wavelengths. Hence they are most likely to receive the greatest damage.

Earthquake More deaths Less deaths

1993 Maharashtra

Earthquake India

Village of Killari (nearer to

epicentre)

Village of Gulbarga

(further away)

[3] Population

density

If the population density of an earthquake-prone area is high, the chances of many people being killed or injured will be high. During the earthquake of Anchorage, Alaska in 1964 of magnitude 9.2, the

death toll was only 115 as it had a small and sparse population then

[4] Level of

prepared-

ness

When drills are not conducted regularly in earthquake prone areas and posters not put up to keep people on guard, these people will not be familiar of what to do in the event of an earthquake. Also, if it has been a long time since a major earthquake occurred, they tend

to be less prepared.

Citizens of Tokyo are aware that it is an earthquake prone area but are less

prepared compared to other parts of Tokyo as the last major earthquake

was in 1923.

[5] Type of soil

People who live in areas with soft soil tend to be affected more greatly on areas of hard solid rock. Soft soil tends to amplify the effects of an earthquake, infrastructure more

likely to cause damage

These places are hence at a risk of greater damage than other towns and

cities around it Earthquake More damage Less damage

1985 Mexico

City Earthquake

Mexico City (further away from

epicentre, but lies on soft soil)

Acapulco (nearer to epicentre,

but lies on hard soil)

TOPIC 2: WEATHER AND CLIMATE

1. Weather and Climate and their elements

Weather The conditions in the atmosphere at a specific place over a relatively short period of time

Climate The average atmospheric conditions of a specific place over a considerable period of time (>30 years)

Temperature The degree of hotness and coldness of a place

Maritime effect The effect large ocean bodies have on the climate of coastal areas (that causes coastal areas to have a smaller temperature

range annually)

Continental

effect

The effect that continental surface have on the climate of inland areas (that causes inland areas to have a larger temperature

range annually)

Altitude The height of a point above sea level. Where A = x m, θ = (32.5 - 0.0065 x) °C

Relative humidity The proportion of water vapour present in the air to the maximum amount that the air can hold at a particular temperature

Precipitation Water falling from the atmosphere to the Earth’s surface

Air pressure The downward force exerted by the weight of air per unit area on the Earth’s surface

Deflection The change in the direction of winds by the Coriolis effect

2. Monsoon winds due to the Coriolis effect

Monsoons in greater detail

Southwest Monsoon

June to September

Northern Hemisphere experiences summer with warm air while Southern Hemisphere experiences winter with cold air

Warm air is less dense than cold air

Low pressure develops over Indian sub-continent while high pressure develops over the Australian continent.

Hence the Southwest Monsoon blows from the Australian continent across the Indian Ocean and the Bay of Bengal,

picking up large amounts moisture.

Heavy rains are brought to Southwestern India and Bangladesh, experiencing hot and wet climate

Northeast Monsoon

October to January

Northern Hemisphere experiences winter with cold air while Southern Hemisphere experiences summer with warm air

Warm air is less dense than cold air

High pressure develops over Indian sub-continent while low pressure develops over the Australian continent.

Hence the Northeast Monsoon blows across the Asian continent and Indian Ocean, picking up large amounts moisture.

Heavy rains are brought to Australia, experiencing hot and wet climate

No rain is brought to countries like Bangladesh due to the dry winds from Asia.

3. Types of climate in the world

Tropical equatorial climate Tropical monsoon climate Cool temperate climate

Locations

Singapore (experiences generally lower

temperatures and higher rainfall from

October to March), Indonesia, Malaysia,

Congo Basin of Africa, South America

(N and E), Brazil (NE)

Myanmar, India, Sri Lanka, Thailand,

Taiwan, Vietnam, Pakistan (the

above are TOC areas), Africa (E),

Madagascar, Brazil (N and

E) , Australia (N)

Canada, USA, New Zealand, Japan (N), Europe

(NW), Korea, China (SE area may be affected

by monsoons) (only the above are located in

the N Hemisphere), Chile (S), Argentina (S)

SIMCSA MISTT, VPAMB CUNJEK, CCA

Latitudes Between 10˚ N and S 10˚ to 25˚ N and S 35˚ to 70˚ N and S

4. Factors affecting temperature at a location

# Factor Description Examples / Locations

1 Latitude

At low latitude, Sun’s rays reaching areas near the Equator are concentrated on the Earth’s

surface almost perpendicularly, resulting in high temperatures Tropical equatorial climate

Angle of incidence of the Sun’s rays strike lower latitudes at an acute angle, heating it up more

intensely than higher latitude areas Tropical monsoon climate

Places located further away from the Equator receive less direct sunlight Cool temperate climate

2 Altitude

At lower ground surfaces, air is dense

Contains more water vapour and dust particles

Heat energy escapes from the surface slowly BY ENVIRONMENTAL

LAPSE

RATE

Areas of high altitude At lower ground surfaces, air is more rarified and

Contains little water vapour and dust particles

Heat energy rapidly escapes from the surface

3 Distance

from sea

Land absorbs and loses

heat faster than the sea

as the sun has to

penetrate deeper into the

oceans to heat it up than

the shallower land

During winter, air above land is cooler than the air above sea. The

coastal areas are hence warmer than inland areas. (Coastal area

have cooler summers and warmer winters) Areas at the coast and areas inland

During summer, land is warmer and the cool air from sea brings

the temperature of the coast down. (Inland areas have warmer

summers and cooler winters)

# Factor Description Examples / Locations

4

Aspect (direction

of a slope

relative

to the

Sun)

In N hemispheres, S-facing slopes receive more direct sunlight and are warmer than N-facing

slopes

Cool temperate climate in N

hemispheres

In S hemispheres, N-facing slopes receive more direct sunlight and are hotter than S-facing

slopes

Cool temperate climate in S

hemispheres

5 Length

of day

Longer days More time for the Earth’s surface to absorb Sun’s energy Warmer days -

Shorter days Less time for the Earth’s surface to absorb Sun’s energy Cooler days

6 Winds

Offshore winds (Land breeze)

Areas near coasts Onshore winds (Sea breeze, wind from sea over land near coasts)

7 Ocean

currents

Winds which has blown over a warm current will have its temperature raised -

Winds which has blown over cold current lowers its temperature.

8

Seasonal

monsoon

winds

Moist onshore winds pick up moisture from the

Indian Ocean during the Southwest Monsoon

Dry weather results from May to

September Australia (monsoon)

Cool weather results from May to

September Southeastern China, Taiwan, Hong

Kong, (monsoon) India and

Bangladesh (equatorial) Moist winds blow offshore due to the Northeast

Monsoon from the interior of India

Dry weather results from December to

March

Cool weather results from December to

March Australia (monsoon)

9 Cloud

cover

More cloud cover in wet season reduces incoming solar radiation and outgoing terrestrial

radiation Areas experiencing monsoon winds

10

Varied

Sun

positions

In summer, from about May to July, the Earth’s axis is tilted such that the Sun is

overhead the Tropic of Cancer.

More daylight hours than in winter

Higher temperatures compared to winter

Tropical monsoon climate at the

Tropic of Cancer areas

11

Equa-

torial

climate

Temperature is high all year round Tropical equatorial climate

5. General temperatures in the world climates


Temperature High and uniform throughout the year High and uniform throughout the year High in summer, Low in winter

Statistics

High mean 27°C High mean 26°C High mean -5.5°C to 2.3°C

Low range

25.7°C < T < 27.5°C

Low range but higher than equatorial climate

24.4°C < T < 30.2°C

High range varying from 15°C to 30°C

-19.1°C < T < 19.7°C

Reasons

Mean

1) Latitude

9) Would be higher if not for the thick cloud

cover

Range

9) Cloud cover

11) Temperature is high throughout the year

Mean

1) Latitude

8) Monsoon winds that create

9) More cloud cover

10) Varied Sun positions

Range

9) Cloud cover in wet season

Mean

1) Latitude

Range

3) Continentality

6. Factors affecting rainfall at a location

# Factor Description Locations

A Convectional

rain

Earth’s hot surface heats up the air above it, causing air to rise quickly.

Condensation occurs and clouds are formed.

Heavy rain accompanied by thunder and lightning falls.

Warm air continues to rise and condensation continues to occur, and only eases when moisture is lost.

Tropical equatorial

and monsoon climate

(areas of high

humidity)

B

Relief rain

and “rain

shadow

effect”

Wind picks up large amounts of water vapour from water surface of water body.

Relative humidity of the air increases. Air is forced to rise above the nearby highland.

Air becomes saturated when it reaches a particular altitude and temperature falls.

Relief rain falls on the windward side when the clouds can no longer hold the water droplets.

Air is warmed when the winds descend and moisture is lost. Hence air is dry on the leeward side.

Coastal areas

between a large

water body and a

nearby highland

C

Global

atmospheric

processes

El Nino, abnormal warming of the surface at

Southeastern Pacific Ocean for several weeks, every

three to seven years

Ocean off the coast of South America heats up

Trade winds push warm surface waters eastwards

Peru and South America has more heavy rains

La Nina follows after El Nino, occurring

every three to five years.

Heavy rains are experienced in

Indonesia and Australia

Peru in South

America (equatorial)

Indonesia

(equatorial) and

Australia (monsoon)

7. General rainfall in the world climates


Rainfall High 2343.7 mm High 2146.1 mm Moderately low 525.3 mm

Even 158 < R < 282.8 Distinct 0.5 < R < 751.4 Even 17.4 < R < 80.1

Reasons

A) Relative humidity is high, above 80%.

C) Western South America and Indonesia

receive heavy rainfall during the El Nino

and La Nina periods respectively

8) Monsoon winds and Convectional winds

11) High temperatures cause water to

evaporate rapidly into the air

B) Places to the sea and on windward

slope with receive more seasonal

rainfall

C) Australia may receive heavy rainfall

during the La Nina period

8) Monsoon winds blowing in opposite

directions from September to October

A) Low temp prevents air from holding much

moisture hence low humidity

A) In summer, higher temperatures result in

higher evapotranspiration rates and in rainfall

slightly heavier

B) High when moisture is brought onshore by

winds towards highlands causing relief rain

8. Climate change

Global warming Example

Enhanced

greenhouse

effect

The greenhouse effect occurs when greenhouse gases absorb heat from the Sun’s

rays and trap it in the atmosphere.

With an increase in world population, more greenhouse gases are released and trapped

in the atmosphere.

This enhanced greenhouse effect causes a rise in the Earth’s average global

temperature known as global warming.

Many countries such as Papua New

Guinea and Afghanistan have

been significantly increasing the

world population growth rate,

which stands at 1.17% currently.

Rapid increase in

use of fossil

fuels

Rapid increase in the use of fossil fuels in vehicles and factories has led to high levels

of greenhouse gases released into the atmosphere.

The usage of chemicals like chlorofluorocarbons found in aerosol cans, refrigerators

and air-conditioners, has also contributed to the enhanced greenhouse effect by

depleting the ozone layer.

Many large nuclear power plants

that emit tons of gases to the

atmosphere are built in Korea and

China to accommodate the large

amount of people in their

countries.

Large-scale

clearing of

forests

Large-scale deforestation and forest fires have reduced the amount of vegetation

cover on the Earth’s surface.

Trees and other plants take in carbon dioxide and release oxygen through the natural

process of photosynthesis.

When more trees and other plants are cut down or are destroyed by forest fires, less

carbon dioxide is absorbed from the atmosphere.

Forests are cleared for timber

and mining, and to create land for

other activities such as

agriculture and urban development

Forest fires in Australia and

Indonesia

Global warming Example

Increased

cultivation and

livestock rearing

Increase in the levels of greenhouse gases due to agricultural activities like wet rice

cultivation and cattle ranching.

The cultivation of rice in padi fields and the use of inorganic fertilisers release

methane and nitrous oxides into the atmosphere.

The rearing of cattle and other livestock releases methane into the atmosphere as

the result of the animals’ digestive processes.

Australia is known for high levels

of cattle ranching and large areas

in Southeast Asia grow padi as

food for consumption.

Increase of

domestic waste

More and more domestic and organic waste is being buried in landfills.

The decaying of rubbish produces methane, which adds to global warming as a

greenhouse gas.

Poland produces 3 million tons of

rubbish per year and relies on

many landfills to clear the rubbish.

9. Floods

Natural causes Human causes

Description Example Description

Excessive

rainfall

Tropical monsoon climates

have moist monsoon winds

blow over land

Heavy prolonged rains

Excess water unable to seep

into ground

Rivers overflow banks

In China, the Yangtze

River are usually flooded

as rains wash large

amounts of sediments into

the river, causing rivers to

become shallower.

In China, where rivers

are high, forests in

mountainous regions are

cleared to create land

for housing and wood for

fuel, increasing frequency

of floods.

Clearing of forests increase

deforestation and decrease

vegetation to intercept

rainwater

Bare slopes promote surface

runoff that increases

surface runoff

Forest

clearing

Global

atmospheric

processes

E.g. El Nino, abnormal warming

of the surface at

Southeastern Pacific Ocean

Ocean off the coast of South

America heats up

Trade winds push warm

surface waters eastwards

Peru and South America,

as heavy rains are brought

away from them past the

Pacific Ocean to South

America

Laboratories in Louisiana

has estimated a 1½ feet

increase in sea level

there and parts of

California to ½ foot

increase in sea level in

the next 50 years

Increase in human activities

has enhanced global warming

Ice cover in polar regions

are reduced

Low-lying coastal regions may

face the possibility of

flooding

Enhanced

greenhouse

effect

Storm

surges

Occurs when strong winds

raise waves in the ocean to

high levels

Flood coastal areas when the

giant waves crash

80% of Bangladesh sits on

floodplains surrounding

the river system like

Ganges and 35% less than

6m, prone to storm surges

In London, areas around

River Thames experience

regular flooding due to

urbanisation, increasing

surface runoff

Concrete pavements and

tarred roads has replaced

vegetation and soil

Interception of rain is lower

Groundwater decreases

Urban

development

Natural causes

Description Example

Melting snow

In cool temperate climates, the melting snow releases large amounts of

water into rivers

Rivers overflow their banks when they are unable to hold excess water

St John River in Canada had a flood in 1986

Several homes submerged in flood waters

Families had to be evacuated from flooded areas

Movements of

the Earth’s

surface

Soil may loosen along mountain slopes during an earthquake and cause

landslides

When deposited into a nearby river, it reduces the capacity of the river

and water is made easier to overflow its banks.

Landslide triggered by heavy rains along steep

banks of the Yangtze river in China makes the

surrounding areas more prone to floods

Impact of floods Examples

Lives lost

Floodplains provide fertile alluvium, making them very

attractive for cultivation of crops, and hence densely

populated

More lives are hence lost when a flood occurs at these

lowlands unexpectedly

Heavy downpour led to rising floodwaters in the northern-

central Huai River Basin in China in 2003, claiming 298 lives

and more people to evacuate to elsewhere

Damage to

infrastructure

Homes are ruined and weakened by floodwaters, damaging

property and infrastructure

Disrupts power supply and phone lines, cutting off

communication.

Hurricane Katrina in USA 2005 led to massive flooding of

several states around the Gulf Coast

Flood damage in New Orleans costed around US$44 billion

Diseases

spreading

When people evacuate to makeshift shelters, they are

usually overcrowded, lacking sanitation and drinking water.

Malaria and cholera are common diseases.

Dhaka, Bangladesh 2004, extensive flooding forced people to

take cover in makeshift shelters

Crowded and unsanitary

Environmental

damage

Destruction of trees, other plant life and natural habitats of

animals

Tsunami in Southern Java in 2006 flooded coastal regions to

cause severe damage to coastal ecology like the Pangandaran

Beach

Advantages of floods Examples

Fertile soil for

agriculture

Regular flooding of rivers provides soil along river banks

with fertile alluvium, making the soil suitable for farming

Many people hence live on low-lying plains near rivers

despite the risks.

Nile Delta in Egypt is where crops are commonly cultivated

because of the fertile alluvium deposited and flooded fields

Adaptations to cope with floods Examples

Building

control

Local government draw up maps to show areas prone to

flooding

Developers ensure that flood would not affect the

buildings they construct

Singapore Ministry of Environment of Water Resources requires

ground levels to be raised in low-lying areas

Has successfully reduced flood prone areas from 1970 to 2006 by

90%.

Post flood

management

measures

When a severe flood occurs, the authorities may

decide to evacuate flood victims to shelter.

Victims were evacuated by boats and helicopters to temporary

shelters like the unused New Orleans Airport in Hurricane Katrina

in USA in 2005.

Watershed

management

The watershed is managed directly to deal with floods

Planting of trees and grass on slopes reducing surface

runoff and soil erosion to decrease chances of

flooding

Royal Forest Department in Thailand developed a programme

Detailed plans to conserve vegetation cover, surface runoff and

amount of sediments washed into the rivers and replanting of trees

Flood

insurance

Provides people with financial resources to rebuild

their property if a flood strikes.

People pay different amounts for the insurance

depending on the history of floods in the location.

The government in United Kingdom has a national flood insurance

programme to help reduce financial burden of the people who have

lost their homes due to a flood.

Adaptations to cope with floods Examples Disadvantages

Dykes

Walls of sand, stone and concrete built along river

banks

Increase the capacity of the river

Chances of flooding is reduced

Dykes has been built along

the Yellow River in China

for centuries.

Continual build-up of sediments on river bed

makes channel shallower and water levels to

raise higher over the years.

Sediments regularly dug up from the bed.

Dams

Walls of dams have gates to hold back or release

water from the man made reservoir behind it

Controls the amount of water that flows

downstream

Increases amount of water upstream

Three Gorges Dam in China

was constructed in 2006 to

overcome floods by water

control

The reservoir slows down the speed of

water in the river

More sediments will accumulate in the

reservoir to raise the reservoir bed

Unanticipated floods

Education

and

monitoring

Scientists are able to monitor weather patterns

and issue warnings when a flood is about to occur

Authorities use them to put up warning signs at

flood prone areas.

Evacuation plans to the

safest and fastest route are

created in the USA for the

people to seek flood shelters

on higher grounds

The success depends solely on the people.

If they are complacent and do not see the

importance of flood education, they will be

less prepared when a flood strikes

unexpectedly in their region.

10. Droughts

Natural causes Human causes

Description Examples Description

Delayed or

insufficient

rainfall

This is found in arid areas

like the tropical monsoon

regions near the Equator

Bangladesh and India

when monsoon winds

are delayed due to the

differences in

pressure in Australia

and its continent.

Deforestation in

Amazon rainforest

where miles of exposed

banks are dried up or

eroded by wind

Cleared forests

Ground exposed to direct heating

Soil dries up quickly

Lower transpiration rates

Less water vapour in atmosphere

Fewer clouds

Reduced

forest

cover

Global

atmospheric

processes

E.g. El Nino, abnormal

warming of the surface at

Southeastern Pacific Ocean

Ocean off the coast of

South America heats up

Trade winds push warm

surface waters eastwards

Indonesia and

Australia, as heavy

rains are brought away

from them past the

Pacific Ocean to South

America

Kothariya in India has

experienced droughts

for a decade where

population of 4000 has

used up all water holes

and wells and have to dig

deep into the ground

Rapid population growth

More water needed for homes,

industry and agriculture

Rivers and ground-water will be

more heavily depended on

Livestock will be badly affected in

these areas

Water over

usage

Sahel in Africa is

located near the Equator

and water bodies are

limited

High temperatures and global

warming cause rapid evaporation

Land, lakes and rivers dry

Droughts occur when rain does not

fill water bodies

Enhanced

greenhouse

effect

Impact of droughts Examples

Resources of

water and food

shortage

People and animals die from dehydration and famine due to failing

crops and droughts prevents the necessary conditions for growth

Affecting many developing countries

2006 Ethiopia drought left 737 thousand people

struggling and had to rely on water provided by the

government water tankers

Environmental

damage

Desertification due to prolonged droughts in arid regions

With little or no rain, dry soil is unable to support vegetation growth

Soil is blown away to leave a barren land

Sahara desert expansion in 1968 due to prolonged

droughts, resulting in the loss of trees and greenery

in the environment, promoting global warming

Forest fires and

haze

No rain for a long time

Vegetation becomes dry Easy to catch fire

Winds blow across forests

Blankets cities and haze to produce effects of SO2 and NO2 (Chem)

Australia has frequent droughts that has destroyed

forests spanning many hectares, spreading smoke to

other parts of the world by monsoon winds

Adaptations to cope with floods Examples Disadvantages

Watershed and

agricultural

management

Management measures

like the planting of

thousands of

seedlings and planting

of specially adapted

plants can help to

cope with floods

In Mongolia (water-scarce) laws are

implemented to limit number of trees being

cut down like the use of firewood only

However, some groups in the

world like Kothariya in India do

not have the unity or technology

to implement the laws. They

require the importing of food

and the switch of staple diet,

and the UN would have to supply

these requirements.

Lack of technology Israel farmers plant apple cacti as they

require less water and can bear fruit for up

to 92% of the time

Proper irrigation

techniques

Irrigation brings

water to areas

receiving little or no

rainfall through man-

made channels. Proper

irrigation and save

water for other uses

in droughts.

Turkey farmers use spray irrigation where

precision sprinkers drip small amounts of

water onto crops to reduce water loss and

save water for other uses.

It is hard to find the perfect

irrigation method to suit the

development of the area. For

example drip line irrigation

enables water to seep directly

through the roots effectively,

but is expensive and farmers

may not be able to afford it.

Hard to suit area

development

Cloud seeding

Dispersal of silver

iodide and dry ice into

the sky airplanes to

induce easier

formation of water

droplets and rain

It was used in Malaysia and Thailand in

2005 in hope to end the prolonged

droughts in rain harvests. It eased the

drought by 80%.

However the cost is high and

success is not always guaranteed

as some areas like India may

experience abnormal

atmospheric process and deter

the functions of clouding

seeding.

Guarantee of success

Post drought

management

measures

Countries affected

require assistance

from other countries

or international aid

organisations

US Agency for International Development

(USAID) provided donations of money, food

and water to Ethiopia during the 2006

drought

CHAPTER 3: WEATHER AND CLIMATE & NATURAL VEGETATION

Biome profile (Rainforest, Monsoon and Coniferous) Tropical equatorial rainforest Tropical monsoon forest Temperature coniferous forest

Dense and abundant vegetation growth,

very luxuriant V

Less dense than rainforest, more

open, less luxuriant V Dense and abundant in coniferous trees V

30 m - 50 m

E

25 m - 30 m

C

20 m - 30 m

E

Made up of

tallest trees

To reach out for

sunlight

Fewer non-parastic plants

Evergeen and

found close

together

To withstand strong winds 15 m - 30 m

C Continuous

and inter-

locking

Prevents sunlight from

reaching forest floor

6 m - 15 m

U.

S

6 m - 15 m

U.S

Uniform height

and conical

shaped

Sways instead of toppling Smaller trees with narrow crowns -

Few non-parastic plants

5 m - 6 m S

0 m - 6 m

U.G Little under-

growth

0 m - 5 m

U.G

Tree saplings and woody plants Dense vegetation,

more under-

growth, shed

leaves

Sunlight able

to reach the

ground when

trees

Poorly leeched soils

0 m - 5 m

U.

G

Little sunlight reaches floor

Sparse

vegeta-

tion

Little sunlight reaches the

floor as emergent and canopy

areas spread out like umbrellas

Thin layer of leaf litter

Needle-shaped leaves do not

favour fast decomposition

Examples Tropical equatorial rainforest Tropical monsoon forest Temperature coniferous forest

Canopy

Lianas (thick woody vines, up to 90m), Epiphytes (grows on trees

for support, rainwater and decaying leaves land on for supply of

water and nutrients), Raflessia (parasitic, competes with host

tree, causing the death of the tree)

Teak, sandalwood and sal -

Understorey Shrubs, ferns and small young trees - -

Undergrowth Small plants, ferns, fungi, saprophytes, decaying leaves Thick shrubs, bamboo

(thickets), grasses and herbs Mosses and lichens

Tropical equatorial rainforest

Tropical monsoon Tropical mangrove Temperate coniferous

Diversity

of plant

species

Largest diversity of plant species in

all biomes Mostly hardwoods Made up of halophytes (salt-tolerant plants)

Softwood found in the trees, which grow in pure stands

Useful

species

Keruing, Kapur,

Chengal, Meranti Sal Sandalwood

Avi-

cenn

ia

Son-

nera-

tia

Rhizo-

phora

Bru-

geria

Sea

hibis-

cus

Nipah

palm Fir Spruce Pine

Making furniture For fuelwood For making

incense

Cons-

truction

materials

Me-

dicine

Fire-

wood Charcoal Food

Pa-

per Pulp

Mat-

ches

Fur-

ni-

ture

Chem

. pro-

ducts

Summary

Large variety of

plants due to high

year round

temperatures and

rainfall, 750 species of trees

and 1500 of plants/ha

Fewer species due to

inconsistent rainfall, 200 species/ha

Plants have to be adapted to growing in salt

water

Plants have to be adapted to low

temperatures and precipitation,

1-3 species/area

Density Extremely dense

and abundant

Abundant but less

dense than tropical

rainforest during dry

season

Mostly similar to tropical

rainforest during wet

season

Sparse d

uring dry

season

Dense and luxuriant Not dense

Reasons High temperatures

and rainfall

Crowns do

not interlock

to form a

continuous

canopy,

denser

undergrowth

More

abundant

leaves

Plants lose/sh

ed

their leave

s High temperatures

and rainfall

Canopy competes

continuously for sunlight

resulting in sparse

undergrowth

Low temperatures and

precipitation

Tropical mangrove Tropical equatorial rainforest Tropical monsoon Temperate coniferous

Leaves S

ecre

te

exce

ss s

alt

Abso

rb

salt

and

st

ore

them

in

old

le

aves

Char

acte

rist

ics

sim

ilar

to e

quat

oria

l cl

imat

e

Ever-green

No shedding of leaves

Large and

broad

Waxy with drip tips

Deciduous (shed leaves during dry

season)

Bamboo plant have narrow leaves during dry season

Mostly

evergreen

Needle-like

Store water during winter

Reasons

Avi

cenn

ia

Son

nera

tia

Rhiz

ophor

a

Bru

guie

ra

High

cons-

tant

rainfall

through

-out the

year

Constant

rainfall,

loss of

water

need not

be highly

reduced

To

maximise

surface

area for

photo-

synthe-

sis

To allow

rainwater to drain

off easily to

prevent bacteria

from growing on

them (as high

temperatures

promote growth

of bacteria)

To minimise

loss of

water

through

trans-

piration

To minimise

of loss water

through

transpiration

due to lack of

water during

dry season

So th

at photosynth

esis

can occur all the tim

e

To

reduce

loss due

to

trans-

piration

The

ground

will be

frozen

and

little

water

available

To regulate the

amount of salt in the

tree as they grow in

salt water

Flowers

and

fruits

Avi. Brugeria Rhizo- Colourful and sweet smelling, present all

year round Usually only present during dry season

Bear cones

Colourful

bright red

lantern

shape -

Attract

insects: for

pollination

phora

Fruits Waves/ Male Female

Traits

and Pros

currents carry

buoyant fruits to

new

places to

take root

elongated,

sharp tips

- Anchor

firmly in

muddy soil

Still air at canopy area do not allow

pollination to be carried out by wind and

can only rely on insects for pollination

and animals for dispersal

They are leafless during this period

Produce

pollen

Produce seeds

(dispersed by

wind or animals)

Protect the seeds from

the cold

Bark and

branches

Thin and smooth

barks

Branches found

only on the top

one-third of the

trunks

Thick and coarse

Located

around the

middle of

trunks

Thick

barks

Flexible

branches

Conical

shape

(some)

Pros

No need for

protection against

cold or dry

conditions

Emergent and

canopy layers

branches spread

out like umbrellas

to get maximum

sunlight

Protects

trunk from

heat and

dryness

during dry

season

Withstand

extreme

heat from

natural

forest

fires

Sunlight

better able

to reach the

lower parts

of the

forest

Protect from

long cold w

inters

Snow can

slide off

easily

prevent-

ing

breakage

With

stand

strong wind

s by

swaying

Tropical equatorial

rainforest Tropical monsoon

Tropical mangrove Temperature coniferous

Roots

Shallow and spread widely

Buttress roots

present Deep roots

Aerial roots / Pnuematophores (exposed during low tide)

Prop / Stilt roots Kneed roots

Shallow and spreading roots

Pros

Roots do

not need to

reach deep

into soil for

water and

nutrients

To

support

the great

weight of

the trees

To tap

water

sources

deep under

the ground

Avicennia Sonneratia Rhizophora Brugeria

To absorb water easily

from soil surface when

snow melts, as during

winter, snow falls instead

of rain

Peg-like,

thick base

Pencil-like, able

to grow 30m high

To anchor trees

firmly in muddy soil,

protecting coastal

areas from strong

waves

To provide

firm

support on

soft soil

Exposed during low tide and able

take in oxygen from the air

during this period

Roots are specially adapted to oxygen-deprived soil

Reasons

Leaf litter decomposes

and humus form to

supply nutrients to the

topsoil

Rainfall is

not regular

throughout

the year

The trees grow on soft and waterlogged soil that lacks oxygen

Precipitation is low

throughout the year,

resulting in little water in

the ground

Biome profile (Mangrove)

Zone Coastal zone Middle zone Inland zone

Species of trees Avicennia and Sonneratia Rhizophora Bruguiera

Types of roots Aerial roots / Pnuematophores Prop / stilt roots Knee-like roots

Tolerance in salt water

Shor

e

Sanility

Inundation (water

cover)

Soil stability

Density of leaves

Distance from sea

Increases

Increases

Functions of forests

Habitat

for flora

and

fauna

Habitat for

people Water treatment

Green lungs of

the Earth Medical uses Water catchment

Protecting

coasts

Preventing

floods

Home to

more than

half the

species in

the world

About 60

million people

live in tropical

rainforests of

SA, SEA &

Africa

Mangrove forests

process waste

materials like dead

animals and human

waste carried by

water

Forests

prevent global

temperatures

from rising

Some plants in

forests have

medicinal value,

which some has

yet to be fully

explored

Enable water to be

collected, stored and

maintained

Mangroves

are able to

protect

coastal

areas

Roots

reduce

chance of

the river

overflo-

wing banks

Quantity

maintenance

Quality

main-

tenance

Tigers

and rare

animals

Tropical

rain-

forest

in Penin-

sular

Malay-

sia

Grizzly

bears

Coni-

ferous

forests

of

North

America

Hunter

gatherers

Korubu tribe

in Amazon

hunts wild

animals

Gathers

leaves for

subsis-tence

Shifting

cultivators

Grow crops

on forest

land cleared

by burning

Roots of mangrove

trees help trap

waste materials

and filter water

before it flows

into sea

Soil contains

bacteria that can

break down

biodegradable

waste, converting

into nutrients for

themselves

Some countries

channel sewage

portions to

mangrove forests

to treat waste

During

photosyn-

thesis

Forests take

in carbon

dioxide, a

greenhouse

gas produced

by humans

Release

oxygen,

replenishing

oxygen supply

This helps

regulate

temperature

on Earth

Sarawak

Calophyllum has a

compound that

may be able to

prevent full-

blown AIDS

Brazillian

rainforest

Quinine from

Cinchona in can

be used to treat

malaria

Coniferous forests

Cough syrup

from barks of

Eastern white

Pine trees

Leaves and branches

intercept rain falling on

ground surface

Acts as a

barrier

from

strong

waves

and

storms

In 2004

Indian

Tsunami ,

it pro-

tected

coasts of

Southern

India

from

destruc-

tion

Soil

erosion

is slower

Soil

makes

the river

bed

shallower

Ability

of the

river to

contain

the

water is

in-

creased

with

roots

Less surface

runoff More

groundwater

Rivers and

reservoirs

Vegetation

transpires to

release water

vapour into

the

atmosphere,

encouraging

cloud

formation and

rain

Less

soil

par-

ticles

are

wash

ed

into

near-

by

rivers

and

reser

-viors

Rnfst

Mnsn

Mngr

Cnfs

Functions of forests

Research and

education Chemicals Food Recreation Timber

Fuelwood and

charcoal

New medicines and

varieties of crops

developed

Some useful

chemicals are

extracted from

forests

Forests also

provide people

with food (e.g.

Borneo:)

Provides ecotourism to

many city-dwellers

Timber can be used to

make furniture and paper

and construct buildings

Wood and charcoal is

used for cooking and

heating for 2 billion

people in the world

New medicine and crops

Banana, coffee and

cocoa are cultivated

for food, new ones are

constantly discovered

Effect on ecosystems

on life

Scientists study

interactions between

forest, animals and

plants like the effect

of weather

Mangrove trees

in East Africa

Tannin from

Rhizophora

treat leather

Tree sap

Black dyes

Pine and fir

trees

Resin Wood

varnish and

ointments

Sago from sago

palm

High in starch

concentration

Edible ferns

Midin

Forests provide

the perfect

location for

animal hunting

Wild deer for

meat

Rafting, hiking and bird-

watching is engaged so

that the environment is

not harmed

Otherwise, tourists

entering the forests

have to follow rules and

regulations

Tamam Negara in

Malaysia is promoted as

ecotourism to gain

income while protecting

the forest

Tropical forests

Chengal and meranti

trees

Rattan for furniture

and baskets

Coniferous forests

Pine trees

Mangrove forests

Leaves of Nipah palm

can be made into

thatched roofs

Monsoon forests

Bamboo for buildings

Less developed

countries like Asia

and Africa gather

wood from forests

as fuel

Rhizophora is being

cut down to make

charcoal in the

Matang Forest

Reserve in

Peninsular Malaysia

Rnfst

Mnsn

Mngr

Cnfs

Causes of deforestation

Forest fires

( Forest fire control)

Most of the forest fires are deliberately set up by people

Plantation companies start forest fires to clear large areas of rainforest for growing oil palm

Some of the fires are also due to dry weather

Vegetation debris that are left on the forest floor like branches and twigs catch fire easily

Caused deforestation of more

than 23750 km2 of Kalimantan

between 1997 and 1998

Demand for

agricultural

landuse

Causes increase in demand for land which result in population pressure in area near forests

New settlers near forests permanently clear forests to grow crops in small holdings

Small farms such as rice and cocoa are grown for own use, for sale and profit

Indonesian government population

programme eases overcrowding in

islands like Java and Sumatra

Causes of deforestation

Growth of

settlements

As population increases and settlements become crowded, more land is cleared for

housing

People start moving from rural settlements to urban settlements to live and

work due to more opportunities for employment

Rainforests are cleared

Balkapapan in East Kalimantan is a business

centre for many national companies dealing with

mining and oil extraction and this reduced the

are from 98.7 km2 to 35 km2 in one year

Improved

transport

networks

Roads and railway tracks are constructed to link settlements in Kalimantan

Allow access to previously remote forested areas in Kalimantan

Lengths of forest trees had to be cut down to clear the path

Trans-Kalimantan Highway between Balikpapan

and Banjarmasin is 230 kilometres long and cuts

through rainforests. This has made it easier for

people to destroy more forest areas.

Growth of

industries

( Logging control)

Logging (timber being cut down and sold)

Pace of logging is increased by timber companies to ensure that the processing

facilities are fully utlitised

Mining (extraction of gold, silver and copper underneath the forests)

Vegetation has to be cleared to expose the ground underneath

A large hole has to be created, exposing loose soil

1656 km2 of forest is removed West

Kalimantan annually

A mining company was awarded a contract to

mine 1290 km of the rainforest since 1980.

Large expanse has been cleared.

Problems caused by deforestation

Loss in

biomass

/diversity ( Af/reforestation)

Stored energy of the organisms represents the total amount of food available on Earth

Ability of the rainforests to support various plant and animal life is reduced as the food chain is

adversely affected.

Survival of herbivores and carnivores will be threatened due to the loss of plant food sources.

Biodiversity of plants and animals in the Kalimantan forests are reduced

Extinction of species in

the Kalimantan may result.

The Proboscis monkey in

the Kalimantan rainforest

is being endangered.

Changes in

the

nutrient

cycle

Less leaf litter

Less decomposed

material

Slower fertility rate

Lack of vegetation cover

No protective cover for soil

Soil exposed to rain and erosion

Loss of soil nutrient

Roots are absent

Absorption of rain reduced

Soils are leached topsoil becomes

infertile cannot support growth

Little of original

vegetation can be replaced

back and cleared land is

unsuitable for cultivation

Vast

changes in

water

Droughts - Less transpiration Cloud formation is reduced Rainfall is lowered

Floods - Roots are not present Soil is loose Eroded and goes into rivers Decrease river

capacity

Muddy waters - Increased amounts of soil Increased sediment level of rivers Unclean waters

Acidity of rivers - Increased amounts of soil Increased sediment level of rivers Water

becomes more acidic Inversely affects aquatic life in the rivers Less fish catch by fishermen

Droughts have been

caused during 1997-98

Severe floods in 2001 in

Samarinda and

Balikpapaen

Problems caused by deforestation

Air

pollution

Dust and smoke released during clearance of trees by burning, causing air pollution If more severe, the

particles were be suspended in air and be blown by strong winds Haze found in other areas like

Southeast Asia from Central Kalimantan, many suffered from eye, nose and throat irritations

Flights had to cancelled to

the Southeast Asian region

due to poor visibility in 1997

Summary of the adaptations of forests

Tropical Rainforests Tropical Monsoon Forests Mangrove Forests Coniferous Forests

Large and broad

To maximise surface area for

photosynthesis

Waxy with drip tips

To allow rainwater to drain off easily

to prevent bacteria from growing on

them

Branches found only on the top one-

third of the trunks

Emergent and canopy layers branches

spread to get maximum sunlight

Colourful and sweet smelling fruits

To use insects for pollination and

animals for dispersal

Roots shallow and spread widely,

buttress roots present

To support the great weight of the

trees

Deep roots

To tap water sources deep under the

ground as rainfall is not regular throughout

the year

Thick and coarse

Protects trunk from heat and dryness

during dry season and withstand extreme

heat from natural forest fires

Waxy with drip tips

To allow rainwater to drain off easily to

prevent bacteria from growing on them

Deciduous (shed leaves during dry season)

To minimise loss of water through

transpiration

Bamboo plant have narrow leaves

To minimise of loss water through

transpiration due to lack of water during

dry season

Leaves able

secrete or store

excess salt

Regulate the amount

of salt in the tree

as they grow in salt

water

Flowers are

generally colourful

To attract insects

to pollinate flowers

Specially adapted

roots

Like aerial, prop and

kneed roots to grow

on soft and

waterlogged soil

that lacks oxygen

Needle-like

To reduce loss due to transpiration

Leaves able to store water

The ground will be frozen and little

water available during winter

Flowers bear cones

Protect the seeds from cold

Thick barks

Protect from long cold winters

Flexible branches

Snow can slide off easily preventing

breakage

Mostly conical shaped

Withstand strong winds by swaying

Shallow, spreading roots

To absorb water easily from soil

surface when snow melts, as during

winter, snow falls instead of rain

Nutrient cycle

dissolved in rainfall from atmosphere

LITTER decomposes tissue fallout BIOMASS

surface runoff

leaching nutrient transfer to SOIL plant uptake

weathered from rocks

Nutrient cycle characteristics in forests

Equatorial rainforest Temperate Coniferous forest

Biomass Largest store of mineral nutrients Relatively low (unsorted)

Total mass of living

organisms, mainly

plant tissues

Tall, dense and rapid vegetation growth Composed of

several layers

of plant species

Needle-like leaves Littler undergrowth

High annual temperature,

with high and even rainfall

Year long

growing season Limited variety of species

One layer of coniferous

trees only

Litter Limited despite continuous fall of leaves

Largest store of mineral nutrients Total amount of

organic matter (e.g.

humus and leaf litter

in soil)

Hence rapid decomposition of dead vegetation

Hot and wet climate provides ideal environment for bacterial

action

Soil Rich in nutrients but easily leeched and washed by runoff Contains few nutrients (unsorted)

Naturally occurring

unconsolidated or

loose covering Earth’s

surface

Soil has to rely on replacement of nutrients from chemical and

biological weathering of the bedrock

Lost through leeching

and surface runoff

Low temp restrict the rate of

chemical weathering of parent

rock, slow replacement rate

Litter content is rapidly reduced

Low fertility

potential of podsol

soil of tiaga

Needle-like cuticles discourage

decomposers and breakdown of leaf

litter to humus

Summary of the functions of forests

Tropical Rainforests Tropical Monsoon Forests Mangrove Forests Coniferous Forests

1. Habitat for flora and fauna

2. Habitat for people

3. Green lungs of the Earth

4. Medical uses

5. Water catchment

6. Preventing floods

7. Research and education

8. Food

9. Re-creation

10. Timber

11. Fuelwood & charcoal


2. Chemicals

3. Food

4. Recreation

5.Timber

6.Fuelwood and charcoal


8. Habitat for people


10. Water catchment


1. Water treatment


3. Water catchment

4. Protecting coasts



7. Timber


2. Green lungs of Earth

3. Medical uses


5. Chemicals

6. Recreation

7. Timber

Measures to reduce deforestation

Forest fire

control

Implement policies to make it

illegal to clear forests by

burning

Conduct annual forest fire

awareness campaigns

Indonesian government introduced measures to

to monitor forest fires through forest fire

campaigns in 1996 and National Fire management

plan in 1999

However, some plantation companies

continue to burn for profit as it is

the cheapest way to clear land

Some local people are also too used

to their traditional farming methods

inherited from the past

Affores-

tation and

reforestation

Plant trees on area not

originally covered with

forests

Plant trees in formerly

forested area cleared by

logging

Afforestation is carried out on agricultural lands

located on fringes of villages and existing forests

MOF set out to restore 900 000 hectares of

forests annually in Kalimantan through the

Forests and Land Restoration Initiative with local

people involved in the replanting of trees

However, rates of the forests being

replanted are slower than the forest

being cleared as the incentives may not

be attractive enough for the people to

participate in the projects

Logging

control

Careful management of

forests with the use of law

enforcement, education and

research programmes

Severe penalties such as

fines and imprisonment are

enforced for irresponsible

timber companies for illegal

logging

Ministry of Forestry (MOF) has arranged for

education and research programmes for timber

companies

Selective cutting is encouraged so that much of

the forest is undisturbed

However, it is difficult to monitor

logging and detect illegal logging

activities due to the lack of

manpower and remoteness of the

forest

Some places has allowed illegal

logging to go undetected

Also, trees selectively removed may

also affect un-removed trees

Conservation

Careful use of resources like

forests to protect them from

destruction

MOF sets aside nature reserves like the Betung

Kerihum Nature Reserve (Heart of Borneo)

WWF works closely with Kalimantan, Brunei and

Malaysia to protect the reserve

However, it is difficult to monitor

logging and detect illegal logging

activities due to the lack of

manpower and remoteness of the

forest

Treasure Island at Risk reported the

presence of illegal logging in 2005

TOPIC 4: RIVERS

1. River terminology

Drainage basin the land area drained by the main river and its tributaries

Watershed the imaginary line acting as a boundary separating one drainage basin from the

next one.

Channelisation the process of changing the natural course of a river to make it flow in a

specific path so as to reduce possibility of flooding.

Wetted perimeter the perimeter of river channel in contact with water

2. The hydrologic cycle map

Refer to Annex A

3. Factors affecting river energy

River velocity

Channel

shape

Rivers with the same cross-sectional area but with different shapes have different velocities

The larger the wetted perimeter, the greater the friction, the lower the erosion, the

slower the speed

Channel

slope

Channel slope refers to the steepness or gradient of the the channel

The steeper the slope (the higher the course), the greater the velocity of the river

Channel

pattern

Three common types of patterns are the straight pattern, the meandering pattern

and the braided pattern

The lower the amount of friction, the faster the flow of water in the river

Channel

roughness

Channel is uneven with items like boulders and vegetation

These items increase the amount of friction, thus decreases the velocity of the

water in the river

River volume

Size of

drainage

basin

Larger drainage basins have generally more tributaries that increase the volume of

water in the main river

The larger the drainage basin, the greater the discharge

Climate

Higher temperatures increase evapotranspiration rates and result in a lower

discharge in the river

Higher precipitation result in more volume of water in the river to cause a higher

discharge in the river

Permeability

of rocks

More permeability of rocks increases the infiltration of water into the ground and

reduces surface runoff

Places with low permeability include concrete pavements in urban areas and places

with asphalt roots

When discharge exceeds river capacity, flooding occurs

Presence of

vegetation

Vegetation intercepts and absorbs rainwater when it rains, increasing the

infiltration of water and reducing surface runoff

Elements of a hydrograph

Hydrograph The graph of the amount of river discharge against time during a specific

stormy period

Rising and falling limb The gradient of the discharge increase from start of storm to peak of storm

Lag time The time taken for the storm to reach the peak of the storm from the start

Peak discharge The greatest discharge during any period of the storm

4. Erosion, depositional and transport methods

a. Transport (TS3)

Traction involves rolling and sliding of large particles like boulders along river bed

Saltation moves bedload and small materials like pebbles downstream by bouncing

Suspension transport of silt, clay, sand and other particles without the touching the river bed

Solution chemical action of river water in dissolving soluble rocks (limestone/CaCO3)

b. Erosion (CASH by vertical or lateral erosion)

Corrasion wearing down of a river bed and banks by grinding action of rock fragments carried by

the river

Attrition load carried by river is being broken as rocks collide with each other, becoming

smoother and rounder in the process

Solution chemical action of river water in dissolving soluble rocks (limestone/CaCO3)

Hydraulic

action

loosening, breaking, dragging, tearing away and removing of rock particles from the river

bed and banks by the sheer force of running water

c. Deposition

Why

At the lower course, river velocity is low and energy level falls.

The river is unable to transport its load and it will be dropped and deposited.

Larger particles are dropped first as they require more energy to be transported

When

When there is a decrease in river velocity, when floodwaters recede, or when a river

enters a sea or reservoir or lake, there will be a significant drop in river energy,

causing the river to lose its ability to transport its load.

Where

At the inner bend (convex bank) of a meander (slip-off slope)

Floodplain when floodwaters recede

At the river mouth where a delta is located

5. Landforms on rivers

a. Erosional

Waterfall

rocks of different resistance

erode less resistant rocks faster

change in gradient

sudden fall in height

great force

hydraulic action (impact of water)

abrasion (rocks swirling at the base)

deepening the depth of the waterfall

Plunge pool

further hydraulic action

and abrasion results in a

deep depression known

as a plunge pool

excavated, enlarged and deepened by hydraulic action

turbulent water at base of water

rock particles swirl about

further erodes the depression

Gorge (it is

a deep,

narrow and

valley with

steep,

almost

vertical

sides)

river flows

through less

resistant rocks

vertical erosion

is faster than

the wearing

away of the

sides of the

valley

flows to the edge of the cap rock of limestone

water increases velocity a excavates a plunge pool at the bottom

armed with rock debris

backsplash at base of waterfall

undercuts cliff face of less resistant sand and shale

erosion of the cliff face

overhanging cap rock loses support and collapses

continuation of the process cause the waterfall to retreat

and form a deep, narrow and long valley known as a gorge

b. Erosional and depositional

Meanders (loops in the

course of a

river)

Areas of regular-spaced deeper water

pools and shallower water riffles

Less friction in pools

Greater velocity and erosive power

More friction in riffles

Lower velocity and more deposition

Continuous erosion and deposition

accentuate

Slight bends of a river

Further erosion and deposition

Bends are more pronounced

Loops known as meanders form

River cliffs

and slip off

slopes

Difference in velocities across channel

Unequal pressure and energy distribution

Currents in a river bank moves in a corkscrew

manner, repeating a series of rotations

Current from outer concave bank descends

downwards

Undercuts and erodes materials

Continuous erosion causes some eroded

materials are slumped down a river, forming a

river cliff on the concave bank.

Some eroded materials are

also carried along the bed up

to inner convex bank

Deposited there

Continuous deposition makes

the convex bank shallow

Resultant slack water

encourages further deposition

A gently-sloping slip-off slope

is built up

c. Depositional

Floodplains (a

wide low-lying

plain found on

both sides of a

river) and

levees (natural

embankments

found along river

banks)

Heavy rain

Amount of water will be

more than the river

capacity

Water overflows its banks

Floods surrounding areas

Once out of the channel,

there will be more friction

Velocity is reduced and energy decreases

Deposition

Larger, coarser and heavier materials are

deposited at river banks and accumulate to

form raised embankments (levees)

Smaller, finer and lighter materials are

deposited further away from the river banks

and accumulate to form the floodplain

Ox-bow lakes (horse-shoe

shaped lake)

Continuous erosion of concave bank

and deposition of the convex bank

Pronounced meander formed

Two neighbouring banks get closer

Narrow neck of land formed

Continued lateral erosion eventually

erodes the narrow neck of land

Outer banks merge

Water now flows straight through the

straighter river channel

Instead of the cut-off abandoned

meander loop

Deposits start to build up at both ends

of cut-off

Seals it off from the main channel

Cut-off becomes an ox-bow lake

Stabilised by vegetation or dried up

Delta (a flat

alluvial platform

found a a river

mouth nearing a

sea)

River mixes with water upon entering sea

River velocity decreases and river loses

energy

Deposits alluvium load of gravel, sand,

silt and clay

The clay consolidates with salt water and

sinks to the bottom

When tidal currents are not strong

enough

And when coastal waters are shallow

enough

Mass of alluvium built up from sea

bed and rises above the water

forming extensive deposits deltas

A flat alluvium platform is

formed and obstructs the flow of

water

Water is forced to find another

way around and hence overflows

banks into distributaries

Levees built up

Stabilised by vegetation

6. Channel management strategies (pros, examples, cons)

Strategy Description Example

Realignment (straightening

of the river

channel)

i. Removes meanders

ii. Reduces length

iii. Increase river velocity

iv. Flow away from an area more quickly

v. Wash away sediments which have accumulated on the river

bed

vi. Deepens the channel

vii. Channel capacity is increased to hold more water

viii. Localised flooding is minimised

For example, the

Mississippi River in

the USA has been

shortened to up to

240km to reduce the

threat of flooding.

Re-

sectioning (widening and

deepening of

the river

channel)

i. Widening and deepening of river channel ii. Increases channel’s ability to hold water

iii. Increases amount of surface runoff as more surface

runoff can enter without flooding

iv. Soil of river banks can be replaced with cement and granite

v. Less friction between water, river bed and banks

vi. Increase rate of water flow away from a section of the

river

Singapore River has

been extensively

altered by widening

and deepening the

channels through

dredging. This is an

effective long-term

measure.

Gabions and

revetments

i. Built along river channel

ii. Divert flow of water to centre

iii. Protects banks from being eroded by force of running water

iv. Reduces amount of sediment flow into the river

Revetments built in

Jamuna and Megna

Rivers in Bangladesh.

Vegetation

planting and

clearance

i. Planting vegetation along river

ii. More roots of trees present

iii. Hold soil together firmly

iv. Improves stability of channel

v. Minimal destruction to natural habitats

Embankments of the

Mekong River

stabilised with

mangroves planted

along river by a joint

initiative by Laos,

Cambodia, Vietnam

and Thailand.

Strategy

Disadvantage

Realign-

ment

Re-

sectioning

Gabions and

revetments

Vegetation planting

and clearance

Building of

dykes

Costly and labour intensive Requires technological

know-how Deters the growth of

marine life like corals Aesthetically unpleasant

and affect tourism Sediments may accumulate

behind these structures and

may lead to flooding, have

to be maintained regularly

May add stress to the banks

and causes the banks to

collapse

Strategy

Disadvantage

Realign-

ment

Re-

sectioning

Gabions and

revetments

Vegetation planting

and clearance

Building of

dykes

Woody debris can become

erosion agents and

encourage flooding

Continual build-up of

sediments on river bed

makes channel shallower and

water levels to raise higher

over the years

Sediments have to be

regularly dug up from the

bed

7. Summarised pros and cons of dams (refer to Geography file)

Pros Cons

Hydroelectric Power Generation Silting

Domestic Water Supply Salanisation

Flood Control Destruction of habitats

Transport and economic value Resettlement of people

Recreation Spread of diseases

Destruction of delta downstream

Water pollution

Annex A

Inputs

Precipitation

Stores and flows

1. Return flow

2. Interception

3. Surface water

storage

4. Infiltration

5. Soil water storage

6. Percolation

7. Groundwater storage

8. Groundwater flow

Interception

Transpiration

by plants

1

2

3

1

4

Water is taken through

the roots to reduce volume

of river as less water

enters the river

Reduces the

amount of

water that

reaches the

river

Outputs

1. River runoff

2. Evaporation

3. Transpiration

TOPIC 5: COASTS

1. Wave terminology

Crest The highest part of a wave formed between two troughs

Trough The lowest part of a wave formed between two crests

Wave height The vertical distance between the wave crest and wave trough

Wave length Horizontal distance between two wave crests or troughs

2. Coast profiles terms

offshore (not visible

even during low tides) foreshore (zone of contact

between sea and land) backshore (exposed all

the time) shoreline

cliff

high tide level

low tide level sand

coastline

rocks

sea

3. Factors affecting wave energy

Wind effects

Duration of wind The longer the wind blows, the larger the waves will be.

Speed of wind

Since waves are formed as a result of high wind velocities across the

surface of the water they are proportionate.

The higher the wind speed, the bigger the waves.

Sea effects

Fetch

It refers to the expanse of sea that a wave travels through before reaching

land. A larger fetch will allow the wave to gain more energy.

Depth of sea

Water particles in a wave are in a circular motion.

A deeper sea would mean that the particles are able to move more freely as

compared to shallow sea, where a lot of friction is encountered.

Hence the deeper the sea, the less friction, the greater the size of the waves,

and the greater the wave energy.

4. Erosion, depositional and transport methods

a. Transport

Longshore drift (refers to the

movement of

sediments parallel

to the coast by the

action of waves

reaching the coast

at an angle)

Winds usually travel towards the coast at an angle.

Prevailing winds cause the waves to hit the coast at an oblique angle.

When the waves reach the beach, the waves break and topple over, causing

surf containing sediments to run up the beach as swash.

The surf then runs back down the beach as backwash perpendicular to the

coast due to the influence of gravity.

The sediments in the backwash are later being carried by a second swash.

This continuous motion of swash and backwash result in transport of sediments

in a zig-zag fashion by longshore currents.

b. Erosion (W.CASH)

Wave

refraction

Wave refraction occurs when waves approach an irregular coastline in a parallel

fashion.

Wave energy is concentrated on promontories such as headlands, erosion

occurs.

Corrasion Waves and rock debris lash against the base of cliffs, scouring and

undercutting the rocks.

Attrition

Rock particles carried in the water knock against one another, reducing one

another in size.

The load is hence more rounded, evident from beach deposits.

Solution

Rain water is a weak acid, and may be further acidified with acid rain.

When it reacts with limestone containing calcium carbonate, it gradually

weakens the whole rock structure, causing it to disintegrate.

Hydraulic action

When waves surge into cracks and joints in rocks, air is trapped in the rocks

and would be temporarily compressed.

When the waves leaves the rocks, there would be a sudden expansion of the

trapped air, exerting a force on the rocks.

Alternate contraction and expansion weakens the structure of the rock overall,

resulting in the disintegration of the rock.

c. Deposition

Where

Gentle waves

Heavy load

Erosion opposing

factors

*Indented

coastline

Presence of vegetation

Sheltered, less windy coast

*Gently sloping shorelines

*Source of beach sediments (e.g. headlands)

Why

Indented coastline

Wave refraction occurs

Waves travel a larger distance to the bay compared to the

headlands

Dissipated wave energy encounters more friction and diverges

at the beach as they spread

Gently sloping

shorelines

Swash is stronger than backwash

More deposition than erosion

Source of beach

sediments More active erosion occurs at the headlands

5. Landforms at coasts

Landform Method of production

Sea cliff

When waves repeatedly pound

against a rocky coast, rocks are

weakened to form lines of

weaknesses in the rock face

A notch forms

Further eroded to form a sea cave

The overhanging part of the cave

eventually collapses with repeated

pounding

A cliff is formed

Wave cut

platform

As a cliff continues to be eroded

by waves, it retreats inland

Over time, a flat or gently sloping surface

known as a wave cut platform is formed


Headland

When waves approach coasts of

differing alternating

resistance, the less resistant

rocks are eroded at a faster

rate than the more resistant

rocks

Differing rates of erosion of rocks produce

an uneven coastline

Less resistant areas of rocks curve inwards to

form bays

More resistant areas of rocks protrude out

from the coastline to form headlands Bay

Beach

Rocks of different resistance builds

up at headlands and bays

Wave refraction at the headlands

cause wave energy to be dissipated at the bay

Materials eroded form headlands

together with materials carried by the

waves get deposited and accumulate at the bay

Over time, a beach forms

Berm

As constructive waves run up the

beach slope, it loses energy

Load is deposited

Swash is stronger than backwash

More materials deposited then

removed

During a storm, waves are stronger

and beach sorting occurs

Coarser heaver materials are hurled

further up the beach slope and deposited

there as the weaker backwash does not

have the energy to remove them, forming

the berm

Finer lighter materials are carried

seawards by the backwash and deposited

near the water’s edge

Spit

Longshore drift

Prevailing winds

Waves to hit the coast

at an oblique angle

Waves breaking

obliquely at the shore

move materials

Along the shore in a zig-

zag manner known as

longshore drift...

Due to backwash and

swash (more on 4a)

Spit formation

Abrupt change in the

coastline causes the

longshore drift to lose

energy due to shallower

waters

Sediments are deposited on the sea floor developing

an under water ridge

Over time, they extend further

Currents are not strong enough to wash the deposits

away

Lie undisturbed

Hooking

The second most dominant pushes the tip landwards

to give it its hooked appearance

When the wind slackens, the spit continues to extend.

The strong current carries the sediments out to sea

and prevents the spit from extending further.

Strong winds again pushes the end of the spit

inwards to give its second hook

Tombolo formation

When an extension of a spit joins an offshore island

to the mainland, and tombolo is formed

Tombolo

Notch

When waves have short wavelength and large

wave height, they form destructive waves

Waves attack rocks of varying resistance by C,

A, S and H along an exposed or uneven coast.

Bays and headlands form

Waves concentrate their energy on headlands

Increased wave erosion form a cliffed headland

The waves attack lines of

weaknesses by CSH (no A)

[elaborate each].

Waves continually attack

these weak rock joints

A notch is formed at the

base of the headland cliff

Cave Prolonged wave action The notch is gradually enlarged, forming a sea cave

Wave cut

platform

Over time further wave erosion

along the cave may cause its roof

to collapse forming a steep cliff

face

As the steep cliff retreats due to continued

erosion, undercutting the base of the cliff

A gently-sloping land strewn with eroded

rocks called a wave cut platform develops.


Arch

The cave and wave up

platform is slowly enlarged

and lengthened

When the cave undercuts the base fully to the

other side of the headland, it cuts through the

headland, forming an arch

Stack

As the sides of the arch are being eroded by

wind and wave forces, the arch loses its

support and collapses to the wave cut platform

An isolated pillar of rock called

a stack is left behind and

separated from the headland

Stump Continual erosion by strong winds and

destructive waves reduces the stack to a stump

This stump is only revealed at

low tide and covered at high tide

6. Waves

What happens as waves hit the

shore?

1) Waves approach the shore

2) Water depth generally

decreases

3) Friction with seabed increases

4) Circular motion of waves is

retarded

5) Waves slowed down

6) Length decreases

7) Crests bunch up

8) Wave height and steepness

increases

9) Top of wave topples over

10) Surf runs up the beach as

swash

11) Percolates into the beach

12) Runs back down as less strong

backwash

Waves

hitting a

straight

shore

No indentation

Waves hit the shore at an oblique angle in

direction of the wind

Friction near the coast

Waves get shallower

Retards the speed of waves

Waves break almost parallel to shore (longshore

current)

Transport of sediments increase

Waves

hitting an

irregular

shore

Headland

Waves reach headland first before entering

bay

Wave refracted at headland concentrates

energy there

More intensive erosive power of C, A, S and H

Bay

When waves move towards the bay, it tends to

curve away across the bay area

Energy is dispersed

Eroded material at the headland is deposited at

the boy area

Constructive waves Destructive waves

Energy Low, resulting in low flat waves High

Coastal

waves Swash more powerful than backwash

Backwash more powerful than swash, surf

pounds on sand but does not run far up the beach

Coastal

process Deposition Erosion

Ability Able to push material up the beach

to form a berm at the top of the beach

Able to dig out material and carry it out

offshore

Offshore Low wave length and height High wave length and height

Frequency Low (6-8 per minute) High (>10 per minute)

Coast

approach Gentle surging waves Steep plunging waves

Association Gently sloping coasts Steep sloping coasts

7. Coastal protection strategies

Type Strategy Description Example Disadvantage

Hard

Seawalls

i. Wall made of concrete built

in front of a coast

ii. Absorbs energy of the

waves

iii. Protects the coast against

strong waves, especially

during storms

Build at long

stretches of

coasts in

England to

reduce rate

of erosion of

land

Waves are redirected

downwards to the base of

the seawall as waves break

Strong backwash wears

away the base, weakening

and collapsing it.

Expensive, S$3 million per

kilometre

Break-

waters

i. Granite materials acting as

breakwaters are placed off

and parallel to the coast

ii. Creates a zone of shallow

water between the coast

and itself

iii. Breaks the waves before it

reaches the coast

iv. Reduces wave energy

Singapore

beaches like

the East

Coast Park

and Siloso

beach at

Sentosa

Unable to provide

complete protection as

some areas are still left

unprotected

Expensive, each

breakwater is S$1 million

Groynes

i. Low wall built perpendicular

to the coast

ii. Prevents materials from

being transported away by

longshore drift

iii. As sediments accumulate at

the side of the groyne

Groynes built

at Sussex in

the United

Kingdom

The beach will not be

replenished by materials

carried by longshore

drift

Beach further down the

coast may be eroded

away

Spoils the natural beauty

of a coastal environment

Gabions

i. Wire cages containing small

rocks to form a wall

ii. Protects the coast against

erosion

Chichester

Harbour in

the United

Kingdom

Can be easily destroyed

by powerful waves during

storms

Wires rust easily

Soft

Stabilising

coastal

dunes (Ridge of sand

piled up by

wind usually

extending

many

kilometers

and heights to

100 metres)

i. Ridge of sand piled up by

wind

ii. Provides protection to

human property

iii. Provides a habitat for many

animals

iv. Plantation of vegetation

along coasts

v. Roots trap and bind sand

together, preventing sand

from being blown inland

Omaha Beach

in New

Zealand

Marram grass

Property development

and recreational

activities can damage the

coasts

Causes the sand to be

easily blown inland

Can easily cover nearby

roads, farms and

buildings

Planting

mangroves

on the

shore

i. They have prop roots that

anchor trees firmly in the

muddy soil

ii. Bind loose soil and protect it

from erosion

iii. 2004 Tsunami showed that it helps

2005 Malaysian

government

launched project

to protect

4800 km of

its coastline

Require cooperation of

the people in the local

area

Have to be mindful not

to let animals like goats

enter the plantations

Type Strategy Description Example Disadvantage

Soft

Beach

nourish-

ment

i. Large amounts of sand are

added to a beach that is being

eroded

ii. When longshore drift removes

sand from the coast, people

bring in sand from other areas

and deposit it onto the beach

24 kilometres

of the Miami

Beach of the

United States

was renewed

This method usually lasts

for only about 10 years.

Beach quality sand is

expensive

Miami Beach project

costed S$105 million

Encou-

raging

growth of

coral

reefs

i. Masses of rock like

substances calcium carbonate

from living organisms

ii. Speed of waves approaching

the coast is reduced

iii. Most of original energy of

waves is lost

iv. Protect beaches against

coastal erosion

Pacific and

Indian Oceans

where water

is warm and

clear

Dynamite fishing, sand

mining and land

reclamation can destroy

coral reefs

Water pollution hinders

growth of coral reefs

Malaysia, for example,

banned fishing in

protected areas

CONCLUSION: MAPWORK AND PATTERNS

1. Map-work materials

Long ruler Set square Protractor Calculator String Pencil Eraser

2. Formulas

Gradient Vertical Distance (Make use of the contour lines, make sure line corresponds)

Horizontal Distance (Make use of long ruler and multiply with scale accordingly)

Always express as a fraction or ratio with the numerator as 1 and denominator 3 sig. fig. if not exact

3. River and drainage patterns

Dendritic Trellis Radial Centripetal

dep

ict Main river resembles tree

trunk and tributaries

resemble branches

Resembles pattern

formed by bricks on a

wall

Move out from

centrally elevated

location

Rivers move towards

of a focal point or

depression

feat

ures

River flows over areas of

same rock types

Rocks are made up of

alternate bands of

resistant and less

resistant rocks

River originates

from the top of a

steep hill, mountain

or volcano

Usually towards a

volcano crater

forming a crater

lake

dia

gram

Opposite direction

from radial,

resembling spokes of

a bicycle wheel

4. Common unique rivers

Centripetal rivers Waterfalls formed by faulting

Rivers around Lake Toba in Indonesia Victoria Falls along Zambezi River in South Africa

5. Weather patterns (describing from climograph)

Mean Range/Distribution Seasonality Extreme months

Tempe-rature

Mean annual temperature

of climograph is high at

26.8ºC

Annual

temperature range

is low at 1.7ºC

Temperature is

hot throughout

the year...

...with the hottest

months in May and

June at 27.5ºC

Rainfall Mean annual rainfall

shown is very high at

2343.7 mm

Rainfall is well

distributed...

...with no dry

season

The highest rainfall

in December at

282.2 mm

Identify From the temperature and rainfall data, it can be seen that the climograph experiences

a hot and wet climate throughout the year and is likely an equatorial climate.

6. Weather descriptors

High Moderate Low

Mean temp. Above 20ºC 10ºC to 20ºC Below 10ºC

Temp. range Above 15ºC 5 to 15ºC Below 5ºC

Rainfall Above 2000mm 1200 to 2000mm 750 to 1200mm 250 to 750mm Below 250mm

7. Earthquake patterns

Zones

Oceanic Oceanic

Mid-

Atlantic

Mid-

Atlantic

Continental Continental

East

African

Rift

Valley

East

African

Rift

Valley

Oceanic Continental

Hima-

layas

Hima-

layas

Oceanic Oceanic

Mariana Mariana

Continental Continental

Andes Andes

Transform Earthquake Boundaries

San

Andreas

San

Andreas

South

America North

America Africa Arabian

Indo-Austra-lia

Europe Nazca Pacific Philip-pine

When Relation to factors Why Features

Velocity

drops

Channel shape When there is an increase in wetted perimeter

Channel slope When there is a sudden change in gradient Floodplains

Channel pattern When the river flows into a calm lake or sea Deltas

Volume

drops

Size of drainage

basin

When little or no rain enters a river

Permeability of

rocks

When the river flows across permeable rocks,

allowing sinking in of water

Climate When the river flows across a desert when

evapotranspiration rates are high

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