Unit 2 : Our Planet "Earth"
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Unit 2 : Our Planet “Earth”
2.1 The blue planet
2.2 Earth’s interior and plate tectonics
2.3 Understanding tsunamis
2.4 Beach erosion
2.5 What’s in air?
2.6 Air pressure
2.7 Air pollution
2.8 Greenhouse effect
2.9 States of water
2.10 Water pollution
2.11 Tides
2.12 Seasons
2.13 The solar systems
29
THE EARTH
2.1 The blue planet
THE SOLAR SYSTEM
We are on the
surface of the
Earth. Trees
and animals live
on the surface. We also find water
forms on the Earth
such as rivers and
oceans.
The Earth is the only planet we know of with the right environment for living
things to exist. The Earth has features which support life. It has oxygen which
animals and plants need to breathe.
We need air as well as water for survival. Most of the Earth’s surface (around 70%)
is covered with water. Earth is the only planet where water can exist in the liquid
form on its surface. As we have so much water the Earth is called the ‘Blue Planet’.
Allah knows
whatever is on land
and in the sea.
30
THE BLUE PLANET
Some land forms
on Earth are
• Island
• Valley
• Mountain
Island Valley
a
Scientists believe that the Earth is
4 ½ billion ( 4,500,000,000) years
old.
Mountain
Some water forms on Earth are
• Ocean
• River
• Pond
• Lake
Ocean River
Pond Lake
31
THE EARTH
Activity 1a: Making a globe
What you need:
• Ball (Tennis)
• Glue
• Copy of a map
• A pair of scissors
•
• What to do:
• Cut out from the dotted lines (you will find a map at the back of the
book).
• Glue one end of the strip to the ball.
• Roll it around the equator and join ends.
• Fold the points at each pole and stick down.
• Take care to fold opposite points together.
32
THE BLUE PLANET
Activity 1b: Reading the globe
What you need:
• Large globe
What to do:
• Locate the seven continents
• Locate the five oceans
• Locate the Maldives
• Locate the equator
• Locate different countries of
interest to you
a
Continent
A continent is one
of the several large
landmasses on Earth.
?
Discuss
■■ Earlier day’s people thought
that the Earth was flat. Do you
think the Earth is flat or round?
Why do you say so?
33
THE EARTH
2.2 Earth’s interior and plate tectonics
We live on the outer I think the inside of the
surface of the Earth. Earth is very hot. The
What do you think is temperature is probably
inside the Earth? high.
That is a good prediction. Through prediction
scientists also figured out what is inside
the Earth. They also drilled deep into the
Earth to get rocks.They also collected rocks
from volcanoes and observed waves from
earthquakes. With all the data they predicted
that inside the Earth must be very hot.
Scientists believe the Earth is made up of three layers; crust, mantle and core.
Below is the model of the inside of the Earth that scientists have built.
The outside layer of the Earth is Crust
called the crust. The crust is the
part of the Earth that we can see.
It is the part that we can touch.
It is the part of the Earth that we
walk on.
The crust is made up of rock and
soil. It is very thin compared to
the other layers.
Under the crust is a layer called
the mantle. The mantle is made
up of rocks and metals. Some
of these rocks are so hot that
they are in the form of liquid.
a
Outer core
Iron, copper and aluminium
are examples of metals.
Mantle
Inner core
34
EARTH’S INTERIOR AND PLATE TECTONICS
Sometimes the hot melted rocks in the mantle shoot up through cracks in the
crust. This is called a volcano.
Under the mantle is the core. The core is the center of the Earth.
The core has two parts, the outer core and the inner core. The outer core is so hot
that the rocks and minerals are in liquid form. The inner core is also very hot, but
it is a solid.
?
Discuss
■■ No one has ever been to the core of the Earth. Why do
you think this is so?
■■ If you dig a hole through the center of the Earth to
travel from Maldives, where will you reach?
■■ Predict what might happen along the journey?
Activity 2a: Layers of the Earth
What you need:
• Hard boiled eggs
• Plates
• Napkins
• Knife
What to do:
• Imagine the egg as the Earth.
• What does the egg shell represent?
• Tap the egg lightly on all sides. You would be able to see the
inside of the egg now.
• What does this layer represent?
• Cut the egg into two.
• Name the layers.
35
THE EARTH
Activity 2b: Making a model of the Earth
What you need:
• Small ball of clay (yellow, red, orange, blue and green)
• Plastic knife
What to do:
• Roll a ball of red clay about 1 inch (2.5 cm) in diameter.
• Cover the red ball with a layer of yellow clay. Try not to
disturb the red layer.
• Cover the yellow ball with a layer of orange clay.
• Cover the orange clay with a thin layer of blue clay and green
clay.
36
EARTH’S INTERIOR AND PLATE TECTONICS
• Cut the model in half.
• The model represents the layers of
the Earth. Explain to your friend
what the red, yellow orange, green
and blue parts represent.
Earth floor: Plate tectonics
Plate tectonics theory states that the Earth’s outer crust is composed of moving
plates. According to the theory, Earth’s outermost layer is broken into seven large
solid pieces called plates. Volcanoes, earthquakes, mountain ranges and islands are
all a result of this movement.
37
THE EARTH
2.3 Understanding tsunamis
Our islands are
vulnerable to That is true. The
environmental recent tsunami
changes. We need left us shocked.
to take extra We need to be
precautions in ready for any such
taking care of our disasters.
islands.
Waves are usually caused by wind motion. The sea waves that you see carry energy.
Earthquakes can also send waves of energy through water.
What are tsunamis?
Tsunamis are enormous waves caused by seismic activities such as earthquakes and
volcanoes. Tsunamis can travel at great speeds across an ocean with hardly any
energy loss.
a
Earthquakes are the
shaking, rolling or
the sudden shock of
the Earth’s surface.
Volcanoes are
mountains that
open downward to a
pool of molten rock
below the surface of
the Earth.
38UNDERSTANDING TSUNAMIS
Activity 3a: Creating waves
What you need:
• Slinky
• Large piece of cloth
What to do:
• Create waves using a slinky spring. Hold both ends of the slinky and
push the slinky back and forth or up and down.
• Create waves using a large piece of cloth.
39THE EARTH
Activity 3b: Finding out how big the waves are?
What you need:
• Large tank filled with several inches of water
• Rocks of different sizes
• Balls and other objects that can be dropped into water
• Stopwatch
• Ruler
What to do:
• Mark the level of the water in the tank.
• Drop a rock into the tank.
• Now measure the increase in height of the water.
• Record the time taken for the water to reach the edge of the tank.
• Repeat this with different sizes of rocks and other objects.
You may use the table below to help you.
Objects Time in seconds Height in centimeters
Rock
40UNDERSTANDING TSUNAMIS
• What can you say about the size of the object and the time taken for the
wave to travel?
• What can you say about the size of the object and the size of the waves?
• What happened to the objects on the side of the tank when the waves
hit them? Imagine these objects represent homes and villages.
• Imagine that you lived on the side of this tank and never expected the
water to go above the highest wave.
How would you feel upon seeing a wave caused by an earthquake
approaching your shore?
?
Discuss
■■ What are the impacts of tsunami
on our lives?
Activity 3c: Creating a poster
What to do:
Create a poster on tsunami aftermath: focus on the devastation caused by the
recent tsunami.
You may look into
• loss of shelter and property
• damage to the environment
• reaction of people.
41THE EARTH
2.4 Beach erosion
Yes, it is. Beach
erosion is a common
environmental issue
for most of the islands.
We have beautiful beaches. Sometimes it happens
However, I have seen in because of our actions.
many islands the beach
being eroded. It is really
sad to see this happening to
our beaches. Is the beach
eroding in your island?
Beach erosion is the movement of sand carried by wind or wave to a different part
of the beach or into the ocean.
We do see the sand that is eroded from one side of the island being transported to
the other side of the island. A number of factors contribute to beach erosion. Wind,
waves and current patterns can contribute to beach erosion. These are natural means
of erosion.
1. Wind removes the sand where there
are few trees on the shore line.
2. Waves that lash against the shore
loosens the sand and the ocean
current carries away the sand.
42BEACH EROSION
3. Unfortunately human activities too contribute to beach erosion.
Human actions that contribute to beach erosion are
• Taking sand from the beach
• Taking coral from the reefs
• Cutting trees and plants near the beach
?
Discuss
■■ Some islands have a sea wall around parts of
the island to protect the island. Explain how
sea walls protect our islands?
■■ Explain how taking sand, corals and cutting
trees can contribute to beach erosion.
43THE EARTH
Activity 4a: Beach Erosion
What you need:
• Tank or large tray
• Water
• Sand
• Pebbles
• Hair dryer or a small table fan
What to do:
• Make a model of an island using the sand.
• Keep the fan or hair dryer at one end of the tank.
• Blow air from this end.
• Observe the sand. What happens to the sand?
• Change the speed of the fan and observe what happens to the sand?
• Place the pebbles on the sand and blow air. What do you observe?
• What can we conclude based on these observations?
Activity 4b: Visiting a beach
What to do:
Visit a beach and observe the surroundings carefully. Observe the beautiful things
that you see on the beach. Look for unpleasant things or events that you may see
on the beach. Make a note of these (if you wish, take photos).
Design a leaflet or a poster that could be used to help people think about how to
maintain beaches.
In your leaflet or poster highlight on how to keep the beach clean and ways
through which we could reduce beach erosion.
44BEACH EROSION
Eroded beach
Activity 4c: Eroding shores
You are to investigate how the sea affects shores.
What you need:
• Jug
• Water
• Tank or deep clear dish
• Sand
• Spoon
What to do:
• Discuss how you could carry out the investigation. You will need to
explain how you would create shallow and steep slopes.
• Note your observations and explain your observation. You may use
diagrams to assist your explanation.
45THE EARTH
2.5 What’s in air?
The air has a gas called I know that air has
oxygen, which is needed oxygen and carbon
by living things. Do you dioxide. May be
know any other gases that there are other gases.
may be present in air? Let’s read and find out
more!
The Earth is surrounded by a layer of air called the atmosphere. The Earth’s
atmosphere is essential to all living things. Animals and plants need air to stay alive.
Other gases
78% of Nitrogen Air is a mixture of gases.
Oxygen The main gases in the
21% of Oxygen air are nitrogen and
oxygen. The remaining
1% of Other gases gases include carbon
Nitrogen dioxide, argon and water
vapour.
Each gas has its own properties. We take in oxygen that is present in air to stay
alive. Oxygen is also needed for combustion.
46WHAT’S IN AIR?
Nitrogen is used by plants for healthy
growth. Likewise, carbon dioxide is needed
by plants to make food.
Look carefully and you will
see the wonderfulness of
Allah’s creations.
Activity 5a: Combustion
What you need:
• Match box
• Candle
• Jar
What to do:
• Stick the candle to a surface.
• Ask your teacher to light the candle.
• Put the jar over the candle.
• Watch the candle burn in the air inside the jar.
• What do you observe after some time?
• Why do you think the flame went off?
47THE EARTH
2.6 Air pressure
We know that air has weight and that
there is a layer of air known as the
atmosphere. What would be the weight
of all the air?
There are several kilo metres of air above the Earth. The weight of this air presses
on everything. This is called air pressure.
?
Discuss
■■ When the air exerts such
high pressure on us why do
not we get squashed?
Sometimes when the airplane flies
high and comes down to land, our
ears ‘pop’ and feel funny. This is due
to the changes in air pressure.
Air pressure is all around us
48AIR PRESSURE
Use of air pressure
Air under pressure is used to operate many devices that require great force. Car lifts
in service stations use compressed air. Air- filled tyres support cars and trucks.
Air pressure and the weather
Air pressure can tell us about what kind of weather to expect. If a high pressure
system is on its way, we can expect cooler temperatures and clear skies. If a low
pressure system is coming, then look for warmer weather, storms and rain.
a
Air moves from areas of
high pressure to areas of
low pressure. This is called
‘wind’.
Ants collect food when they feel a storm is on the way. Changes in air pressure
warn them.
49THE EARTH
Activity 6a: Making a balloon ‘rocket’
What you need:
• Fishing line / string
• A straw
• Sticky tape
• A balloon
• Measuring tape
What to do:
• Thread the straw onto the fishing line or string.
• Tie each end of the line to something stable, such as a chair, a desk or a
post.
• Put a piece of sticky tape over the straw.
• Blow up the balloon. Hold the mouth of the balloon tightly so that air
does not escape.
• Stick the balloon to the tape.
• Let the balloon go! Measure how far it travelled.
• Make adjustments to the balloon, the straw or the line so that the rocket
will travel at least 5 metres.
50AIR PRESSURE
Activity 6b: The Magic Glass
What you need:
• Jar
• 4 x 6 inch index card
• Water
What to do:
• Fill the jar to the top with water and wet the rim slightly.
• Lay the card on top of the jar.
• Hold the card firmly in place and turn the jar over.
• Now take away your hand and see what happens.
• The water should stay in the glass.
• What does the experiment tell us ?
51THE EARTH
2.7 Air Pollution
The roads are How do you think
becoming very dusty. traffic pollutes the
The air we take in will air?
not be good to breathe.
Unlike cities, the air
in my island is really
clean because we have
very few vehicles on
the road.
Air is free for all of us to use, but sometimes due to our activities we pollute air.
Air pollution is the contamination of the air by the discharge of harmful substances.
Air pollution occurs due to toxic gases. These gases could be carbon monoxide,
sulphur dioxide and nitrogen oxides.
Sources of air pollution in the world include:
Industry
Gases from chemical
industries, garages and
dry cleaners.
52AIR POLLUTION
Vehicles Vessels
Gases from trucks, cars, buses, Sea vessels also produce gases that
aeroplanes and machines. pollute air.
Natural disasters Household
Forest fires, sand storms and volcanoes. Uses of aerosol, wood fires, smoking
and fire crackers.
?
Discuss We are the guardians of the
■■ What are the sources of air planet and therefore we
pollution in the Maldives? should take care of the Earth.
■■ How do vehicles pollute the air?
53THE EARTH
Air pollution can cause serious health problems. These include
• irritation of the eyes and throat
• itching nose
• respiratory infections
• eye damage and blindness
• long term respiratory problems such as asthma
• skin diseases
54AIR POLLUTION
Activity 7a: Controlling air pollution
What to do:
• Refer to the picture below.
• Identify what activities contribute to air pollution.
• Based on the picture identify at least two actions that can be taken to
reduce air pollution.
55THE EARTH
2.8 Greenhouse effect
Scientists are
trying to find
Do you really think more information
that our Earth is whether the Earth
warming up? is really warming
up and what are
the impacts of this
to our Earth?
The Earth had relatively stable temperatures for a long time. Light from the Sun
warms land, water and air. The warmed up land , water and air give off heat which
rises towards the sky.
Gases in the Earth’s atmosphere capture some of that heat and prevent it from
escaping into space. This heat trap keeps the Earth at a fairly stable temperature. It
is warm enough for plants and animals to survive. But, for the past 100 years or so,
scientists have noticed that the earth seems to be warming up more than it used to
be. This phenomenon is called global warming.
Scientists believe this is because there are too many greenhouse gases trapped in the
Earth’s atmosphere. When there is more of greenhouse gases, more heat is trapped
in the atmosphere.
a
Earth as a greenhouse
Greenhouse is an all-glass building where
plants are grown. They are warm because
the glass walls allow Sun’s rays in but
prevents the heat from getting out.
Imagine the Earth as being a giant
greenhouse. The gases act like the walls
of a greenhouse. They prevent heat from
escaping into space and the Earth stays
warm.
56GREENHOUSE EFFECT
a
Greenhouse gases
The main gases that cause the greenhouse effect are:
Water vapour
Carbon dioxide
Methane
Nitrous Oxide
Some amount of these gases are important to our Earth. But increase of
greenhouse gases raises the average temperature of the Earth.
?
Discuss
■■ What do you think will happen if the Earth becomes hotter?
Activity 8a: What can you do to slow global warming?
What to do:
Based on the pictures, state what you could do to slow or stop global warming.
57THE EARTH
2.9 States of water
Water exists in three states. It exists as a solid, a liquid and as a gas.
Liquid water is found in many places.
We see liquid water
• coming out from taps a
• when it rains
• in the sea Pure liquid water is free of
salts, rocks, soil and garbage.
When water is a liquid, we can drink it, wash with it, or swim in it.
a
Most of the water we see is
in the liquid form. However,
all of this water cannot be
used by us. Nearly 97% of
all the world’s water is salty
or otherwise undrinkable.
2% is locked in icecaps and
glaciers. Only 1 % is used
for all our needs.
58STATES OF WATER
Water can be a solid.
When water freezes
into ice or snowflakes
it is a solid.
Water can be a gas. When water is
warmed, it goes into the air as a gas.
When water exits as a gas it is called
water vapour.
Activity 9a: Which melts faster?
What you need:
• Ice cubes (big ice cubes, crushed ice)
• Two glasses
• Water
What to do:
• Put water in each glass.
• Put the big ice cubes into one glass. Label this as A.
• Put the crushed ice into the other glass. Label this as B.
• Put the glasses in a warm place.
• Predict which will melt faster.
• Observe both glasses for sometime.
• Was your prediction right?
• Explain your observation.
59THE EARTH
Activity 9b: Dry or Wet
What you need:
• Your hands
• Towel
What to do:
• Dry your hand with a towel. Feel your palm. Is it wet or dry?
• Hold your hand in front of your mouth (about an inch away).
• Breathe out slowly about 10 times on to the palm of your hand. Do not
blow.
• When you are done, feel your palm.
• What does it feel like?
• Is it wet or dry?
• How would you explain the moist feeling?
60STATES OF WATER
Activity 9c: When water freezes
What you need:
• Marker
• Empty Bottle
• Water
What to do:
• Put water into the bottle/jar.
• Don’t fill it to the top.
• Mark the level of water.
• Put the bottle/jar in the freezer.
• Leave it overnight.
• Look at the bottle/jar. What happened?
?
Discuss
■■ How do we get fresh water from underground?
■■ Why do you think the water in some of the islands is salty?
■■ Mountain climbers say that some of the glaciers on top of very high
mountains have disappeared. Why do you think this might be?
We should make a deliberate effort
to look after and thank Allah for the
wonderful creations.
61THE EARTH
2.10 Water pollution
All plants and animals need water. Water is often allowed to become polluted.
All types of water pollution are harmful to humans and animals. Water pollution
may not damage our health immediately but can be harmful after long term
exposure.
Sources of water pollution
Industrial waste
Industrial waste from factories
such as toxic chemicals can
damage the health of marine
animals and those who eat them.
When hot water from power
plants and factories are dumped
into water sources, the water
temperature changes suddenly.
Suspended particles in freshwater
reduces the quality of drinking
water for humans and animals.
This makes such water sources
Domestic Sewage
unsuitable habitats for living
things.
Sometimes water is contaminated by
sewage. Pollutants from sewage can a
infect marine and terrestrial life.
Diseases such as cholera, typhoid and
fever can be caused due to polluted Sewage is wastewater that
water. For these reasons, it is important contains faeces, urine and
to have access to sanitary conditions and laundry waste.
clean water.
62WATER POLLUTION
Marine dumping
Dumping of litter into the sea can cause
huge problems. Marine animals can get
caught in litter and may result in death.
Different items take different lengths of
time to degrade in water.
Effects of water pollution
a
Water born germs can cause diseases
and may lead to death of organisms. Cardboard- takes 2 weeks
For example, water born pollutants to degrade
can enter the food web and cause Newspaper- takes 6 weeks
defects in new born children. Water to degrade
pollution can change the ecosystem, Foam- takes 50 years to
causing death of living organisms. degrade
Styrofoam- takes 80 years
to degrade
? Aluminium- takes 200
Discuss years to degrade
Identify impacts of water Plastic packing- takes 400
pollution on living things years to degrade
Activity 10a: Saving water
What to do:
Refer to the pictures and explain at least three ways by which we can save water.
63THE EARTH
2.11 Tides
Every 12 hours or so, the sea water rises
then falls back again. These rises and
falls are called tides. When the water is
rising, we say the tide is flowing. When it
is falling, we say the tide is ebbing.
The movement of the ocean waters is
caused by tidal forces of the Moon and
the Sun acting on the ocean.
As the Earth turns, the Moon pulls the
ocean water directly beneath it, causing
the water to rise. A similar rise in sea
level occurs on the opposite side of the
Earth, where the water bulges out as a
result of the Earth spinning. At these
places there is high tide.
Some six hours later, the Earth turns by
90 degrees. The sea then falls to its lowest
point and then there is low tide.
Once every two weeks, the Sun and One week later, the Sun and
the Moon line up with the Earth. Their the Moon are at right angles to
combined pull creates a spring tide, each other. Pulling in different
where the tides are higher than the directions, they create a lower tide
usual. than the usual, called a neap tide.
64TIDES
Activity 11a: High and Low tide
What you need:
• Plastic Bowl
• Water
• Ball
What to do:
• Place the bowl on a firm, flat surface, then half fill it with water. Place the
ball gently in the water so that it floats in the middle of the bowl as shown
in the picture.
• Place both hands on top of the ball, and push it down into water gently but
firmly.
• What happens to the level of the water? This shows the high tide.
• Let the ball gently rise again. Now you can see the water in the bowl
dropping gain.
So the tide has risen and fallen even though the amount of water is unchanged.
65THE EARTH
2.12 Seasons
The Earth is tilted on its axis, and the way it is tilted affects the amount of sunlight
different areas receive.
Between mid- March and mid- September the North Pole leans towards the Sun,
and the South Pole leans away from it. From mid-September to mid March the
opposite is true. Warmer weather and long days come to the side of the earth tilted
towards the Sun.
Northern hemisphere
axis
Mid-June Mid-December
Southern hemisphere Mid-September
Seasons are different in different parts of the world.
Some countries experience four different seasons: winter, spring, summer and
autumn., summer and autumn.
Winter
In winter, it is cold. In some places
it snows. The hours of sunlight are
shorter.
Spring
In spring it starts to get warmer.
Plants begin to grow and
produce food.
66SEASONS
Summer Autumn
In summer it is hot. The hours In autumn trees loose their leaves. It
of sunlight are long. starts to become cooler.
?
Discuss Allah knows everything. Not
■■ Why do the length of the a leaf falls without Allah’s
day and temperature range knowledge.
remain the same in the
Maldives?
Activity 12a: Seasons
What you need:
• Flash light
• Dim room
• Table or flat object
What to do:
• Turn the flashlight on.
• Hold it above the table or some other flat object.
• Remember to hold the it close to the table or the object. Can you see a
definite circle of light.
• Notice the size of the circle and the brightness of the light.
• Now hold the flashlight the same distance away from the table or the
object, but at an angle.
• Do you see how much more area the light has to cover when the flash
light is held at an angle?
• How could we relate the experiment to the occurrence of seasons?
67THE EARTH
2.13 The solar system
The solar system consists of the Sun, the planets and a large number of small bodies
such as comets and asteroids. The planets circle around the Sun. The Sun sits in the
middle while the planets travel in circular paths (called orbits) around it.
The diagram shows the different positions of each planet.
The inner solar system contains Sun, Mercury, Venus, Earth and Mars.
The outer solar system contains Jupiter, Saturn, Uranus and Neptune.
Pluto is now considered as a dwarf planet.
?
Discuss
■■ What do you think are the sizes of the planets?
You may refer to the diagram above.
68THE SOLAR SYSTEM
Planets are grouped based on many different features. Two easy groupings are
composition and size.
Composition
Rocky Planets Gas Planets
Rocky planets include Mercury, Venus, Gas planets include Jupiter, Saturn, Uranus
Earth and Mars. and Neptune.
The Rocky Planets are mostly made up of The gas planets are usually made up of gases
rock and metal. (hydrogen and helium).
These are very heavy and move very These planets are light for their sizes and
slowly. move very quickly.
They do not have rings and have very few They have ring systems and have many
moons. moons.
Size
Mercury, Venus, Earth and Mars are
considered as small planets and Jupiter,
Saturn, Uranus and Neptune are
considered as giant planets.
We can see planets by using a telescope
To think of greatness of Allah,
think about His wonderful
creations.
69THE EARTH
Activity 13a: Gathering information on a planet
What to do:
Select a planet of your interest.
Gather information about the planet
Find out
• the size of the planet
• type of planet
• position of the planet
• has any spacecraft visited the planet
• any other interesting facts about it
Compile your findings into one booklet and present to the class.
70You can also read
