DK Findout! Earth - Maryam Sharif

Earth

Author and consultant: Maryam Sharif-Draper

Project editors Manisha Majithia, Ishani Nandi Contents
Senior editor Cécile Landau
4 What is Earth?
US Senior editor Shannon Beatty
US Editor Jill Hamilton 6 Earth’s atmosphere

Editorial assistant Megan Weal 8 Structure of the Earth
Senior art editor Clare Joyce
Project art editor Nehal Verma 10 Moving Earth
Art editor Jaileen Kaur
12 Mountains
Managing editors Deborah Lock,
Alka Thakur Hazarika 14 Volcanoes

Managing art editors Vicky Short, 16 Earthquakes
Romi Chakraborty
18 Deserts
DTP designers Dheeraj Singh, Ashok Kumar
Picture researcher Nishwan Rasool 20 Water

Pre-production producer Dragana Puvacic 22 Oceans
Production controller Isabelle Schart
Art director Martin Wilson 24 Rivers Meteor
Publisher Sarah Larter 26 Glaciers shower
Publishing director Sophie Mitchell
Li River, Guilin, China
Educational consultant Jacqueline Harris

First American Edition, 2017
Published in the United States by DK Publishing
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ISBN: 978-1-4654-6309-8

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A WORLD OF IDEAS:
SEE ALL THERE IS TO KNOW

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2

28 Erosion and weathering Satellite
30 Caves
32 Record breakers 50 Continents
34 Biomes 52 Rural and urban
36 Conservation 54 Mapping the world
38 Weather 56 Meet the expert
40 Seasons and climate 58 Earth facts and figures
42 Climate change 60 Glossary
44 Soil 62 Index
46 Rock cycle 64 Acknowledgments
48 Rock uses
Tsuna
Political globe of the world

mi wave

Mauna Loa, US

What is Day
In an area of
Earth? the Earth that is DAY
facing the sun, it
Earth is our home. It is nearly will be light, and
therefore day.

94 million miles (150 million km) EQUATOR

from the sun, and is the fifth Equator
This is an imaginary
largest planet in our solar line around the
middle of the Earth.
system. Earth is also the only It lies halfway
between the North
planet in our solar system Sun’s rays and South Poles.
where water is found on the As the sun’s rays
surface, which allows animals reach Earth, they
and plants to live here. provide light and
warmth. Without
the sun, life on Earth
would not exist.

Solar system ! WOW!

Our solar system is made Our sun is
up of the sun and the eight huge—about
planets that travel around it one million times
—Mercury, Venus, Earth, Mars, bigger than
Jupiter, Saturn, Uranus, and
Neptune. The solar system also the Earth!
has moons, comets, asteroids,
and meteoroids zipping through Mercury Venus Earth Mars
it. Scientists estimate that our
solar system was formed
about 4.6 billion years ago!

4

AXIS Axis Earth’s story
This is an imaginary
HTline around which It is thought that Earth, and the
the Earth spins as other planets, formed as gravity
it travels around forced material in clouds of gas
the sun. Earth’s and dust together, creating
axis is slightly tilted. clumps of rock. These gradually
grew bigger to form planets.
Night Over time, the conditions on
In an area of Earth Earth evolved to support life.
that is turned away
from the sun, it Earth’s orbit
will be dark, and
therefore night. This is the path that the Earth takes
as it travels around the sun. Earth’s
NIG orbit does not form a perfect circle.
It is a slightly flattened circle, or oval.
Earth takes 365 days, or a whole
year, to make one complete journey
around the sun.

The number of
days it takes Earth
to orbit the sun

365

Sun

Earth

Jupiter Saturn Uranus Neptune

5

6 370–6,000

Exosphere Satellites 50–370
These orbit Earth in
This is the highest layer of Earth’s the thermosphere and
atmosphere, where it merges into space. exosphere. We use them
Only a few, very thin wisps of gas are to make phone calls and
found this high above our planet. It watch TV. Scientists also
would be impossible to breathe here! use satellites to find out
more about space.
Earth’s
atmosphere Thermosphere

Earth is surrounded by a thick layer Unlike in other layers of Earth’s atmosphere,
of gases, called the atmosphere. These temperatures here increase as you go higher,
gases protect Earth from the sun’s some parts rising to 3,600°F (2,000°C)!
rays, keeping temperatures on our Satellites, including the International Space
planet at a comfortable level. Earth’s Station, orbit Earth in the thermosphere.
atmosphere is divided into a number
of distinct layers. At the outer edge Aurora ! WOW!
of the atmosphere, there is no clear These bright lights appear in
boundary. It just fades into space. the thermosphere when Without some
particles from the sun fall of the gases in its
into Earth’s atmosphere. atmosphere, Earth

would be too
cold to live on!

Mesosphere Meteors
These are bits of matter
The top of the mesosphere is from outer space that
the coldest part of the Earth’s burn up on entering
atmosphere, with temperatures Earth’s atmosphere,
of -226°F (-143°C). Gases here are creating streaks of light.
thick enough to slow down meteors, They are also called
causing them to burn up. shooting stars.

Stratosphere Sun’s rays 30–50

The air in this layer is very Reflected rays Weather balloons
dry and still. The ozone Scientists launch these
layer, which protects plants to collect information
and animals on Earth from about conditions in
dangerous ultraviolet rays
that are given off by the sun,

lies in the stratosphere. Earth’s atmosphere
that affect the weather,

Ozone layer such as temperature 10–30
This thin band, running across the stratosphere, and air pressure.

contains a large amount of ozone, a gas that

Troposphere absorbs ultraviolet (UV) rays from the sun. UV
rays cause sunburn, and can cause skin cancer.

The gases found in DISTANCE FROM EARTH IN MILES

the troposphere make Mountains
up the air that we Some of Earth’s highest
breathe. Therefore, mountains extend quite a

life exists in this layer. way into the troposphere.

Clouds form here, and 0–10

it is where most of Planes
our weather occurs. Planes usually fly in the

troposphere, but may

go up to the edge of

the stratosphere.

7

Structure 2,000–3,700 3,900–4,000
of the Earth
3,700–3,900
Planet Earth is made up of a number
of different layers. Some of these Lower mantle
are solid, while others are liquid or This layer of solid rock reaches
a mixture of both. Knowing about temperatures of up to 5,432°F
Earth’s structure will help you (3,000°C). This is hot enough
understand what is happening
on the surface—where you live. to melt the rock, but pressure
pushing down prevents this.
Looking under Slice of AVERAGE THICKNESS IN MILES FROM THE CENTER OF THE EARTH 750–2,000
the surface section Mantle plume
These clouds
If you could slice a section out of hot gas and
of the Earth, you would see melted rock shoot
its very different layers. up toward Earth’s
surface.
Water
Seas and oceans Outer core
cover about This layer is made of melted
71 percent of metals, including iron, nickel,
Earth’s surface. and sulfur. It can get as hot
as 11,000°F (6,100°C). As
Land 0–750 Earth spins on its axis, this
Just 29 percent liquid metal swirls around,
of Earth’s surface Inside and outside creating a magnetic field.
is land, which is Ocean and land cover Earth’s surface,
split up into but inside are many complex layers. Inner core
continents. At the center of the
Earth is a huge ball of
solid metal—mostly
iron—called the
inner core. It can
reach temperatures
of up to 10,000°F
(5,500°C), as hot
as the sun’s surface.

8

Crust Volcano
Earth’s outer layer, or Volcanic eruptions occur
crust, is also its thinnest when liquid rock, called
layer. The crust is made magma, rises up through
up of solid rock, which cracks in Earth’s crust.
can be divided up
into continental crust Continental crust
and oceanic crust. A mixture of different
rocks are found in this
Upper mantle layer, which forms all
This layer is made of both
solid and liquid rock. It is of the land found on
constantly moving, which Earth. The continental
is why the tectonic plates crust is older than
that form Earth’s crust also the oceanic crust.
move around on top of it.
Ocean
! WOW! All of Earth’s major
bodies of water lie
The direct above the oceanic
journey to the crust, or sea bed.
center of the Earth
is 4,000 miles Lithosphere
This is made of
(6,400 km) solid rock, which
long! is divided into
tectonic plates.

Upper mantle Oceanic crust
The lower part of this This rocky layer under
layer is called the the Earth’s seas and
asthenosphere. High oceans is constantly
temperatures here changing, as tectonic
melt some of the plates move around and
rock. The cooler, solid liquid rock, or magma,
upper part is called rises up from the
the lithosphere. asthenosphere, then
cools and hardens.

9

Moving Earth KEY

Earth’s crust is divided up into large All Earth’s tectonic plates
pieces called tectonic plates. These plates have names. The color
move around on the molten rock under of the line along their
them. Where the edges of these moving edges tells you what type
plates meet, the Earth’s crust is unstable, of boundary they have.
and earthquakes and volcanic eruptions
occur. Mountains may also form there. Convergent

PTtadbterhhilocevaeeutestotnprhengedlraaieeactrnbereepitsoeml,wasiaunath.neiTvenndsorhemdtltevyrtyaeeaphdenderetsismi.fef—efTodeershgrecmeeotis.nrneovhfeorwgent, Divergent

Transform

Arabian Eurasian Plate
Plate
Philippines
Plate

Convergent boundary African Plate

Here, two plates move toward each Indo-Australian
other. They may push together, forming Plate
mountains. But, if one plate gets pushed
under the other, a volcano can form. Antarctic Plate

Continental
plate

Oceanic
plate

10

Ring of Fire Mount Fuji, Mount
Japan St. Helens, US
This area in the Pacific
Ocean is one of the most Nevado del
unstable parts of the Ruiz, Colombia
Earth’s crust. Here, the
tectonic plates move
around a lot, causing
some of the world’s
worst earthquakes. It
is also where there are
many active volcanoes.

Transform boundary

When two plates rub against each other,
this can cause an earthquake. They may
slide by in opposite directions or move in
the same direction at different speeds.

North American Plate

Juan de Caribbean Moving
Fuca Plate Plate plate

Cocos Divergent boundary
Plate
Here, plates move away from each other,
Pacific Plate South and plate material forms in the gap left
American between them. When this happens under
the ocean, new ocean floor is created.
Plate

Nazca
Plate

Scotia Oceanic
Plate plate

Oceanic
plate

11

Mountains Fault-block mountains

Mountains are formed when the Earth’s Cracks in the Earth’s crust can
tectonic plates move and collide with create massive blocks of rock that
one another. As the plates continue then move apart. As they move,
to move, magma and land may be one block may slide under another,
pushed up, forming mountains. pushing it up. This leaves large
blocks of rock sticking up, high
above the Earth’s surface. These
are fault-block mountains.

FACT FILE MOUNTAINS

» Name: Sierra Nevada
» Height: 14,494 ft (4,418 m)
» Location: US

Dome mountains GREETINGS FROM de Dôme

When large amounts of the Puy
magma under the Earth’s crust
bubble up toward the surface,
layers of rock above the magma
are pushed up to form dome
mountains. The inside of these
mountains is filled with magma
that has cooled and hardened.

12

FACT FILE

WISH YOU WHEREimHERaE..l. ayas » Name: The Himalayas m)
» Height: 29,029 ft (8,848
» Location: Nepal

Fold mountains Volcanic mountains

These are the most common A volcanic eruption occurs when
type of mountain. They form magma bubbles up and eventually
when two or more tectonic erupts through a crack in the Earth’s
plates are pushed together, crust. This causes molten rock, known
causing layers of rock on the as lava, to flow over the land, before it
seafloor to crumple and fold. cools and hardens. Further eruptions
Over millions of years, these create more layers of hardened lava,
folded layers are slowly pushed which build up to form a mountain.
up higher to form mountains.

FACT FILE MOUNT

» Name: Mount Kilimanjaro Kilimanjaro
» Height: 19,340 ft (5,895 m)
FACT FILE » Location: Tanzania

» Name: Puy de Dôme
» Height: 4,806 ft (1,465 m)
» Location: France

13

Volcanoes STRMAouTnOt FVujOi, JLaCpaAnNO

Volcanoes form when magma, baoTcSenfohtdnrvleaaeeyhvtr-oaaasyrvhradpeoaneolpmdcnweaeaadenddsr,oh.efweuTutsilhhtpaahearnoitesrdfthteeldaaorevlautplenspasgcotniieofddoroelnoalsesuy.desc.rasn
a mixture of hot gas, ash, and
melted rock, erupts from a crack
in the Earth’s surface. The melted
rock, called lava, flows out and
hardens. As layers of lava build up,
the volcano gets bigger. A volcano
can be active, dormant, or extinct.

! WOW!

Most of Earth’s
active volcanoes
lie hidden from
view, under the

ocean!

Inside a volcano Main Eruption
vent
When pressure in the magma Magma
chamber under a volcano gets too chamber
high, the magma is forced up and
out of the main vent. This is called
an eruption. The force of this
eruption blows rock off the
top of the volcano, creating a
bowl-shaped hollow, the crater.
In some volcanoes, magma also
erupts from smaller vents that
branch out from the main vent.

14

MaunaSLHoaI,EHLaDwaii, US

SsfeatTlrchrhonoohiupaedmnepnlitdnsmtiteiognhvoutguosinhcneilehsdcen,afreartlonesrulvre,esoonsayeellnnecesrdyasdauahsnrplnaaasoetvrg.vxieeeeoasprf.ng.looToesurnshmcsitaevleinyerd

CINDER CONE NgoCroAngLorDo,ETaRnAzania

Paricutin, Mexico ccmwaCahlhuaomalsesmdoitnnesborgatefarlmistitkuhaatenerosedasmcielbovaareolrgltgwaemheprle,.ausceTvpoi.ohrtucliecotuyanolnaffforootr,hhrmcoeellsows,

Csowamifrnietvadholuellessrcstuacetanoealonplny.esdTnivdhmooeetloscyt.asoatnTorcohevoeecimsiooralmneerenreou-tntsp.hhtteaiyoppneeds 15

Earthquakes What causes
an earthquake?
When the rocky tectonic plates that
form Earth’s crust move suddenly, The plates in Earth’s crust constantly slide
large waves of energy spread out, past each other, but can get stuck. Pressure
causing the ground to shake. This then builds up until the plates finally move,
is an earthquake. Some earthquakes sending out shock waves. The focus of an
are fairly gentle and may even go earthquake is the point inside the ground
unnoticed, but others can bring where pressure builds up. The epicenter is
terrible destruction. the point on the surface above the focus.

Epicenter Shock wave

Fault line

Earthquake crack Tectonic plate Focus

An earthquake can cause large cracks to open up 56
in the Earth’s surface. Many are small, no more
than a few feet deep or wide, but others are
massive, and whole buildings can fall into them.

12 2.54

Seismograph Mild tremors

This machine is used to Earthquakes that a seismograph
measure the force of the records as having a force of 2.5–4
vibrations caused by an are felt as mild tremors. They cause
earthquake. It records how little or no damage, although trees
powerful these vibrations may sway and windows rattle.
are on a numbered scale.

16

Italy 2009 Sumatra 2004

In 2009, an earthquake measuring This massive earthquake had
6.3 on a seismograph struck L’Aquila a force of 9.3! It triggered a
in central Italy. Many buildings series of huge waves, called
collapsed and around 300 people died. tsunamis, that traveled for
Thousands of smaller earthquakes, thousands of miles across
called aftershocks, followed. the Indian Ocean, killing
280,000 people.

6.3 7.9 9.3

Wobbling dishes China 2008

When an earthquake A force-8 earthquake
has a force of 5–6, struck Sichuan Province,
windows are likely to China, in 2008. Huge
crack and dishes fall chunks of rock fell down
off shelves and smash. from the mountains,
Some buildings may smashing towns and
suffer serious damage. villages. Tremors were
felt up to 1,060 miles
(1,700 km) away.

17

Hot deserts
Temperatures often reach 122°F
(50°C) or higher during the day in
hot deserts. But at night, it can be
very cold. Most hot deserts are
near the equator, where there is
strong sunlight all year round.

Sahara Desert, Africa

Coastal deserts
Here, cold winds blowing off the
ocean cause thick fog to form and
drift inland. Water droplets in the
fog soon dry up under the hot
sun, rather than falling as rain,
leaving the land below very dry.

Atacama Desert, South America

Deserts ! WOW!

Abnfsaeyuboswrodvrvuaeesitiprsvneyeea,rchittsinhseoo.sittrtThopdhhefleoameyacfyne.aEaisWrmar,erebeaetuahluxsrt’tssearsuaesnoasmumdllrtyehpfelalatyaachtrendiegntriessvykt.eccolOroaifytnvntdeclleeryoesloadderr. ts The largest
desert, the
Sahara, covers
about a quarter
of Africa!

Cold deserts
The largest cold deserts are
in Central Asia, usually in
high, flat areas. They are very
dry, like all deserts, but are
also very cold for most of
the time. During the long
winters, temperatures often
drop as low as -40°F (-40°C).

Gobi Desert, Central Asia

Polar deserts
These are extremely dry
and cold. Temperatures
rarely rise above 50°F
(10°C), even in summer.
Some are covered in ice
and snow all year, while
others are covered in gravel
and large rocks. Most of
Antarctica is polar desert.

Ross Island, Antarctica

Desert landforms Sand dunes Oases Mesas and buttes
These hills are formed Rare underground Sand and grit, carried
Over thousands of years, by the wind blowing water can create pools by the wind, wear away
many different natural across the desert sand, of water. Plants then rock to create these
features, or landforms, have so that it piles up. spring up around them. steep, flat-topped hills.
developed in deserts. These
include hills; mountains;
narrow, steep-sided valleys
called canyons; large, flat
areas called plains; sand
dunes; strange rock
formations; and oases.

19

Water ! WOW!

Water is essential to life on Earth. Without Between
it, plants and animals would not be able to 50 and 65%
survive. Around 71 percent of Earth is of your body
covered in water. This includes both
saltwater and freshwater. Not all of Earth’s is made
water is easily available for us to use. up of water!

29% SALTWATER 0.3%

LAND FRESHWATER Only a small part of
Earth’s freshwater is
71% found in lakes and
rivers. We use it for
WATER washing and drinking.

97.5% 30.8%
Some freshwater
Water on Earth
lies under Earth’s
Most of Earth’s water—97.5
percent of it—is saltwater that surface. This
makes up the oceans and seas.
The 2.5 percent that is left is groundwater
freshwater. This is found in
ice caps, glaciers, lakes, rivers, flows into
and sometimes underground.
lakes and

rivers, so

68.9% we also use
it in our
daily lives.

This portion of Earth’s
freshwater is found in
ice caps and glaciers. It
is therefore very difficult
for us to access and use.

20

The water cycle Sun Water vapor
Condensation cools and
Earth’s water is always moving condenses to
from one place to another. This Evaporation form clouds.
process, called the water cycle,
is a continuous journey, in Rainfall
which water moves between
the land, the atmosphere, Rainwater runs
and the ocean. into rivers, and
finally the ocean.
The sun’s heat makes water
evaporate, or turn to vapor,
which rises up into the air.

How we use water Drinking
Only a small amount
We use large quantities of water. We drink it, of the water a person
wash with it, use it in industry, and also prepare uses every day is for
food with it. Below are the percentages of the water drinking.
that each person uses every day for these activities.
Personal
0.2% Washing, brushing
your teeth, and
4.2% flushing the toilet
use up this share.
30.6%
Manufactured goods
65% Nearly a third of each
person’s daily water is
used to make things. This
includes items such as
televisions and phones.

Food production
This takes up most of
the water we use. Water
is an essential part of
our diet. Without it, our
bodies would not work!

21

Oceans Pacific gree

Around 71 percent of the Earth’s surface
is covered by oceans. Many different and
interesting features are found in and around
them, and a huge variety of animals and plants
have adapted to life in this watery world.

Volcanic islands Nishinoshima vo n turtle
These islands are formed from
layers of magma, or hot liquid rock, lcanic island, Japan Open ocean
which erupts from a volcano under This is the top layer of
the water, then cools and hardens. the ocean, nearest the
The magma layers eventually build surface. The open ocean
up to create an island. is vast. Although food
can sometimes be hard
to find, many animals,
such as dolphins, seals,
and turtles, live there.

Seamounts Oceanic trench
These underwater mountains When tectonic plates
are formed by volcanic eruptions in the ocean floor
on the ocean floor. Most of them move and collide, one
are not erupting. may be pushed under
the other, creating a
Tectonic plates in narrow trench. These
the ocean floor trenches are the
are moving. deepest places in
the Earth’s oceans.

Tectonic plates in
the ocean floor
are moving.

22

G
assic Coast, Dorset, United Kingdom
reat Barrier Reef, Australia Mupe Bay, Jur
Rock pools
Coral reefs When the tide goes out on
These are made from a rocky seashore, pools of
the skeletons left by water are left behind in
tiny sea animals, called holes in the rocks. These
coral polyps, when they then become home to a
die. The skeletons build huge range of plants and
up into huge reefs, animals, such as shellfish
where plants and other and sea anemones.
sea creatures live.
! WOW!
Oceanic ridge
Moving tectonic Nearly 95%
plates can also of the world’s
create underwater oceans remain
mountains. The unexplored!
Mid-Atlantic Ridge,
under the Atlantic 23
Ocean, is more
than 40,000 miles
(64,000 km) long.

Hydrothermal vents
When seawater filters down
cracks in the Earth’s crust, it is
heated by volcanic activity.
Hot water then spurts out
through the cracks or vents.

24 UPPER COURSE Rivers Source
This is where a river starts, high up
A river is a natural channel of freshwater that flows in the mountains. The source, or
across the Earth’s surface. All rivers start in mountains place where the river starts from,
or hills and flow down toward the sea or ocean, or into could be a spring, or a lake, or even
another large body of water. They may be short and a melting glacier. A river can have
more than one source.
narrow, or very wide and flow for hundreds of miles.

Tributary Fast
A stream or river that flows into wing
a larger river, rather than directly
to the sea, is called a tributary. zu Falls, Argentina, South America
Some large rivers have hundreds -flo Igua
of tributaries!
Waterfall
V-shaped valley and gorge Rivers usually flow over a mixture of hard and
Near its source, a river flows very soft rock. The force of the water will wear away
fast. The rushing water wears away more soft rock than harder rock. Where this
the surrounding rock. This widens happens, there may be a steep drop in the
and deepens the river channel, level of the riverbed, creating a waterfall.
forming a gorge or V-shaped valley.

MIDDLE COURSE Meander Fertile floodplains
A meander is a curve or These are flat areas of land next to a
bend in a river. It forms river. Water in a river may increase
when the flow of water for some reason and become too
wears away the land on much for the river to carry. It then
one side of the river, then overflows onto the floodplain. Soil
dumps the broken-down in floodplains is usually very fertile.
rocks this creates on the
other side, increasing the
area of land there.

US, North America
Katmai Peninsula, Alaska,
LOWER COURSE
Estuary or delta Slow-flowing
Near the sea, saltwater mixes with freshwater,
forming an estuary. The land is flatter, so the Li River, China, Asia
river slows down. If it slows down enough, Mouth
mud is deposited, creating a delta with several The river’s journey ends here. It is where
channels that the river now flows through. it finally flows into the sea, ocean, or
other large body of water, such as a lake.

A

Glaciers E

A glacier is a huge river of ice that forms
when thick layers of snow fall on top of each
other and are pressed together. Most glaciers
form high up in mountains, where it’s so cold
that any snowfall never melts. They are
found all around the world, usually in polar
and mountainous regions.

26

B PARTS OF A GLACIER
C
A Cirques are deep hollows near the
D top of a glacier, formed where a
glacier has moved over an area
and worn away the rock.

B Accumulation zones are found
at the top of glaciers, where the
snowfall has built up, often over
hundreds of years.

C Valley glaciers flow through
steep-walled valleys. They
eventually wear down the valley
sides, making them much rounder.

D Lateral moraines are long ridges
of rock, soil, and dirt left along the
sides of a moving glacier.

E Medial moraines are piles of rock,
soil, and dirt that are left behind
where two glaciers meet.

Glacier terminus

The glacier terminus is the
lower end of a glacier. It is
sometimes called the toe or
snout. Some glaciers end
farther down a mountain,
where the ice melts to form
lakes and streams. Others
reach the coast, where large
chunks break off into the sea,
creating icebergs. This is
called calving.

Perito Moreno Glacier, Argentina

27

Erosion

Erosion is the wearing away of rocks and other matter
on the Earth’s surface by a natural force, such as a sliding
glacier, a flowing river, or the wind. Material that is
rubbed off is carried away and deposited somewhere else.

Water erosion
This is caused by falling rain
or flowing water. Rivers, for
example, wear away the land
that they flow over, changing
the surrounding landscape.

Wind erosion Ice erosion Coastal erosion
The force of the wind can remove As glaciers move, they rub away Crashing waves gradually wear
pieces of rock and carry them off. the land under them, carrying the away the rock in cliffs, and sweep
Wind erosion is common in deserts. broken-down material with them. up material from the beach.

28

Biological weathering
This is when plants or
animals cause rocks to
break up. Plant roots often
grow into small cracks in
rocks, splitting them apart.
An animal digging can also
turn rocks into rubble.

Weathering

Weathering occurs when rocks
are weakened, so that they crack
and then break up into smaller
pieces. This natural process can
be caused by rainfall, changes in
temperature, or even by plants as
they grow. There are three types of
weathering—biological, chemical,
and physical.

! WOW!

Water erosion
created the

Grand Canyon in
North America!

Chemical weathering Physical weathering
Chemical reactions can break up rock. Wind, water, and temperature changes
Acid rain, for example, destroys the weaken rock. If water in a crack freezes,
stone in statues and buildings. it expands and can tear a rock apart.

29

Caves

Caves are underground spaces or holes. Some
are large enough for a person or animal to enter.
They form in many different ways, all of which
involve rock in the Earth’s surface crumbling and
wearing away. Caves often have lots of interesting
and exciting features to explore.

Stalagmite
Water dripping onto the
cave floor leaves behind
tiny rocky particles that
were dissolved in it. As
the dripping continues,
these particles can build
up to form a pillar of
rock, or stalagmite.

Solutional caves
These are the most common type
of caves. They are created when a
build up of acidic water dissolves
the rock around it. Holes and
tunnels start to appear, getting
bigger and bigger as more rock
dissolves and is washed away.

Types of caves Thurston Lava Tube, Hawaii, US Lava caves
When lava flows slowly
Caves are found all over our planet. over land around a
Some are small, single spaces, but volcano, it can harden
others contain many chambers, on the surface, leaving
linked by tunnels to form a huge liquid lava flowing
maze of different areas. Although
most caves are found in rock, underneath. This liquid
some form in ice or lava. drains away, leaving a
hollow tube of rock
30 that forms a cave.

Stalactite Soda straws
These hang down like icicles. They form These thin, hollow tubes also form
in the same way as stalagmites, from from dissolved particles in water,
rocky particles dissolved in water, this dripping slowly through the roof
time dripping from the cave’s ceiling. of a cave. They may grow into
stalactites, if the water keeps
dripping for a very long time.

Column
If a stalagmite and
stalactite become long
enough and meet,
they will form a rocky
column. Columns are
also created when a
stalactite grows down
to touch the cave floor.

Skaftafell ice cave, Iceland Benagil cave, Portugal

Ice caves Sea caves
Ice melting on top of a glacier can form a stream These are formed by waves constantly battering
or waterfall that flows through the glacier. against cliffs along the seashore. This leads to
Eventually, this flowing water will hollow out cracks appearing in the cliffs that get larger as
part of the glacier, creating an ice cave. beating waves continue to wear away the rock.

31

Record breakers

Our planet is full of incredible natural wonders, some
of which are millions of years old. From skyscraping
mountains to underground caves, here are five of
Earth’s record-breaking land features.

HIGHEST Mount Everest, Nepal

The peak of Mount Everest
lies 29,029 ft (8,848 m) above
sea level, making it the world’s
highest mountain. It is ten
times taller than the world’s
tallest building—the Burj
Khalifa skyscraper in Dubai.

LONGEST

Nile River, Africa

The world’s longest river
is the Nile, at 4,238 miles
(6,825 km) in length. It flows
through 11 African countries,
from Burundi to Egypt,
where it meets the
Mediterranean Sea. The

Nile takes its name from
the Greek for “river valley.”

32

Krubera Cave, Georgia DEEPEST

The world’s deepest cave lies in
Asia. Stretching down 7,208 ft
(2,197 m), it is nearly as deep as
seven of Paris’s Eiffel Towers.
Russians call the cave Voronya,
meaning “crows’ cave,” after the
many crows nesting at the entrance.

DRIEST

Atacama Desert, Chile TALLEST

Covering 600 miles (1,000 km), this South 33
American desert is one of the driest places
on Earth. Some parts have not seen rainfall
since records began at least 400 years ago!

Angel Falls, Venezuela

Spectacular Angel Falls is the
world’s tallest waterfall. With a
drop of 3,212 ft (979 m), it is
more than twice the height
of New York’s Empire State
Building. American pilot Jimmy
Angel first spotted the waterfall
from the air in 1933.

Biomes Mountains are high places with a cold,
windy climate. It gets colder the higher up
Earth can be divided up into a you go, so different groups of plants and
number of different types of
landscapes. These zones are animals are found at different heights.
called biomes. Every biome is
home to a particular group of
plants and animals that are suited
to the conditions found there.

Deserts

Deserts are very dry because
there is little or no rainfall. They

can be very hot and very cold.
The plants and animals found in
deserts have adapted to living in

these extreme conditions.

Wetlands Rain forests

Wetlands are permanently flooded with Rain forests get a lot of
water. This can be saltwater, freshwater, or rain. Most of them also get
a mixture of both. Swamps, bogs, marshes, a lot of sunlight, and are very
and deltas are all types of wetlands. Many hot all year round. They are home
birds thrive in this environment. to many different plants and animals.
The largest rain forest is the tropical
34 Amazon rain forest in South America.

Coniferous forests

These forests have long, cold, snowy
winters and short, warm summers. Trees
here have adapted to this harsh climate.
They are mostly evergreen, meaning they

stay green all year round.

Deciduous forests GRASSLANDS

The temperature and rainfall in deciduous Grasslands get little rainfall. Only grass and
forests changes from season to season. a few small trees and bushes can grow in
During the fall and winter, most trees these dry places. But many animals, such as
change color and lose their leaves. zebras and elephants, manage to live there.

TUNDRA

It is usually very cold and windy in the
tundra, and there is not much rain. The
ground is often covered in snow, so only a
few plants and animals can live there.

This is the coldest biome on Earth. The
freezing temperatures make it difficult
for any plants to survive. Animals, such
as polar bears, penguins, and seals,
have adapted well
to life here.

Conservation 9

We need to preserve and take good care of
the Earth and its resources—the air, water,
soil, plants, and animals on which we depend.
This is what conservation is all about.

START Learn to conserve! 1 Faucet left running. 8 Wind farm. Move
Miss a turn! forward 2 places!
Play this game to find out more about Water is valuable. It is A wind farm creates
what can harm and what can help essential for life, so never electricity. Wind is a
conserve our planet. Grab a dice and renewable source of
some counters, and get started! waste it. energy, so using it does
not harm the environment.

7

How is our planet affected? 2

When people fail to conserve resources, 3 Saving paper. Move 6 Not recycling.
Earth is affected in a number of ways: forward 3 places! Miss a turn!
If you reuse scrap paper, You are sending too
Energy and buy goods made from much waste to landfill
Fossil fuels, such as oil and coal, are used recycled paper, fewer trees sites. This can damage
up too quickly, and cannot be replaced. will have to be cut down to the soil, water sources,
make more paper. and the atmosphere.
Pollution
Waste gases in the atmosphere trap heat 4 Driving to a friend’s 5
from the sun, so the Earth gets hotter. house. Miss a turn!
Harmful gases from
Water cars pollute the air.
Higher temperatures, along with low Walk or bicycle
rainfall, will eventually lead to drought. instead.

Food
Drought and soil pollution can damage
crops, so there is not enough food.

Forests
Cutting down trees can lead to plants
and animals losing their homes.

Waste
Waste pollutes the environment. Also,
if we waste resources, they will run out!

36

10 Factory waste 11 12 13 Bird sanctuary.
polluting river. Move forward
Miss a turn! 1 more place!
This harms plants A sanctuary gives birds
and animals living and other wildlife
in or near the river. a safe home.

16 15 Destroying forest.
17 Miss a turn!
Animals and plants
that depend on the
forest may die.

14

18 Bicycling to school. 19 20 21 Dropping
Move forward litter.
2 more places! Miss a turn!
Bicycles, unlike Litter can harm the
cars, don’t pollute soil, plants, animals,
the air. and humans.

24 23 Planting trees. 22
Move forward
25 Leaving lights 1 extra place!
on. Miss a turn! Trees remove waste
Electricity is often gases from the air.
made from resources
that can’t be renewed. 27 You’re a conservation expert! FINISH

26 Growing fruit and Congratulations! You now know
vegetables. Move much more about how you can help
forward to finish! make Earth a healthy and happy place.
Growing your own Spread the word—tell your family and
food saves on the friends, so that they can help too.
cost of getting it

to the stores.

37

Sunshine Wind
Heat from the sun warms The sun warms the air to
the air, creating dry, bright different levels in different
weather conditions. places. As warm air rises,
cooler air rushes in to
Clouds replace it, creating wind.
Sunlight warms water in lakes and
rivers, turning it into vapor that rises,
and then forms tiny water droplets
that gather together as clouds.

Weather ! WOW!

Sunshine, clouds, wind, rain, frost, and snow Large raindrops
are some of the different weather conditions can fall to Earth
that we experience on Earth. The sun plays a at speeds of up
major role in the way one set of weather
conditions changes to another set. to 20 mph
(32 km/h)!
38

Rain Snow
Water droplets in clouds When it gets very cold, water
get bigger and become droplets in clouds form ice
too heavy to remain in the crystals that group together
sky. They then fall as rain. and fall as snowflakes.

Extreme weather

We say that we have extreme weather
when conditions are very different from
those that we are used to. Extreme weather
can suddenly appear without warning, and
may last for hours or even days, bringing
death and destruction to an area. Flooding,
heatwaves, blizzards, hurricanes, and
tornadoes are all types of extreme weather.

Hurricane Felix, Honduras

39

Seasons and climate

Earth takes a year to travel, or orbit, around the sun.

At the same time, it spins on its axis, an imaginary Spring is a time of
change between
line between the Poles. This means the amount NG summer and winter.
of sunlight falling on any area of Earth Days gradually get
SPRI brighter, warmer, and
varies during the year, changing the wetter. Leaves start to
grow on the trees and
weather and creating seasons—spring, baby animals are born.

summer, fall, and winter.

How seasons change

Earth is tilted on its axis as it spins and orbits
around the sun. This tilt causes one half, or
hemisphere, of Earth to lean toward the sun,
while the other half leans away. For the half
leaning toward the sun, it is summer. For the
other half, it will then be winter.

The sun shines The sun shines directly
equally on both on the Southern
hemispheres. Hemisphere.

December

March Winter is the coldest
season. Days get
Sun WINT shorter and nights get
longer. Some animals

ER grow thick coats to
keep them warm in
winter. Others just fall
asleep, or hibernate.

September

The sun shines The sun shines

June directly on the equally on both

40 Northern Hemisphere. hemispheres.

Summer is the hottest SUM Climate
season. The days get
longer and the nights MER The climate of an area is the type of
become shorter. Plants weather it usually experiences. It
grow well in the warm includes the amount of rainfall, hours
sunlight. There are of sunshine, and highest, lowest, and
lots of green leaves average temperatures. Earth is divided
on the trees. into climate zones that are based on
their distance from the equator.
Fall is when summer LL
gradually changes into FA TempePraotlearzzoonnee
winter. Temperatures Subtropical zone
start to cool. The TSPeuomblapTtrrreooTzrrppoaoiitncpceeaaiczllaozzloonznneoeene
leaves on the trees
change color to Tropical zone This area is
orange and brown, very hot and damp all year
then fall to the ground. round. It rains a lot and
thunderstorms are common.

Subtropical zone Here,
summers are long, dry, and
hot. Winters are wet, but
usually short and mild.

Temperate zone Extreme
conditions are rare here.
Summers are warm and
winters cold, but not freezing.

Polar zone It is icy and dry all
year round here. Winters are
long and dark, while in summer
the sun shines most of the time.

41

Climate change

Earth’s climate has always changed naturally over time. However,
climate change now appears to be speeding up! Many recent changes
in climate are caused by our modern way of life. Earth is getting
warmer, which can have a huge effect on the environment.

Causes

Humans are thought to be responsible for the most recent, major climate changes.
Waste gases have built up in Earth’s atmosphere due to industry, transportation,
and deforestation. These trap more heat around the Earth, so temperatures rise.

Industry Transportation Deforestation

Whenever we burn oil, coal, or We now use cars, buses, and Trees help remove gases from the
natural gas, waste gases are planes regularly. They all fill the air. So, as more trees are cut down,
released into the atmosphere. more waste gases stay in the air.
air with lots of waste gases.

How can 12
we help?
Renewable energy Transportation
There are many ways you
can help slow down climate Use more energy from resources Avoid transportation that
change. Just by turning off that there are plenty of, such as releases waste gases into the
your computer or the TV
when you’re not using them, sunshine, wind, and waves. air. When you can, bike or
or the lights when you leave a walk instead.
room, or by walking to school,
you reduce the level of waste
gases in the atmosphere.

42

Effects Extreme weather

34 Heatwaves, droughts,
heavy rain, and flooding
are becoming more and
more common, because
of Earth’s atmosphere
warming up.

Rise in sea levels

Higher temperatures melt
glaciers and ice caps. The
water formed eventually
flows into the ocean. Sea
levels rise and areas near
the coast are flooded.

Changing
natural habitats

Many animals live in
special places, such as on
sea ice or in coral reefs.
Warmer temperatures can
destroy both of these, so
animals lose their home.

5

Recycle Save electricity Grow your own food

Recycle plastic, glass, and Stop leaving your computer or the Food grown at or nearer home
paper. This reduces the amount TV on standby, and turn off the saves on the fuel needed to
lights when you leave a room. transport it to local stores.
of waste sent to landfill sites.

43

Soil Leafcutter ants
Ants dig tunnels into
Soil is the layer of loose material between the the soil, letting in air
surface and the solid rock below the ground. and moving around
Nothing can grow on Earth without it, decaying plants and
but the soil varies in different places. animals, which adds
nutrients to the soil.
Grasses
The soil is rich in nutrients,
so many grasses can grow
healthily and quickly.

Forest floor
Many leaves from the
thick tree canopy fall
to the dark forest
floor and decay.

Long roots Dung beetle Buttress roots
Trees and grasses These creatures Trees have shallow
have long roots feed on and break roots underground
that go deep down up, or decompose, to quickly take in the
to collect as much animal poop, adding water and nutrients
water as possible nutrients to the soil. in the topsoil.
from the soil.

Grassland Tropical rain forest

The soil is usually deep and full of The soil is very wet and many plants grow,
nutrients. This is because rotting grass so there is lots of humus to add nutrients
roots help hold the soil together and to the soil. However, these nutrients are
add nutrients for new plants. Plants washed away by the constant rain, leaving
compete for water. shallow, acidic soil.

44

Soil profiles Humus Top soil This dark layer
Dead plants and is full of tiny creatures
Soil is made up of broken rocks, animals decay, and nutrients, which
minerals, decaying plants and adding nutrients, or plants use to grow.
animals, tiny creatures, gases, goodness, to the soil.
and water. If a section is cut Leaching layer
through soil, you will see many Subsoil Water drips through
layers. The depth of the layers This moist layer this layer, leaving
vary in different soils. contains clay and mostly sand and silt.
minerals from the
weathered rock. Weathered rock
Large rocks are broken
up from the solid
bedrock below.

Cactus
Cacti have shallow roots and
thick stems, so they can collect
and store water.

Fall leaves Deep roots
When leaves drop Desert trees have
to the forest floor, very long roots to
they decay, putting reach down and
nutrients back into collect water from
the soil. deep underground.

Earthworm Tree roots Kangaroo rat
Burrowing Roots of deciduous When burrowing,
earthworms mix trees reach animals break
the soil layers, different layers down large rocks,
letting air in and of the soil to mix up the soil,
allowing water to collect water and let air into it.
drain through. and nutrients.

Temperate deciduous forest Desert

The soil is moist and full of nutrients from The soil is very dry and few plants grow,
decaying plants and animals, especially in so there is little humus. It is made up of
fall. The deep roots of plants break up the boulders, pebbles, and sand, and is blown
bedrock, which adds minerals. Water often around by the wind. Any water drains
drains through steadily. through the sand easily.

45

Rock cycle

Rocks go through many changes over time. These
are caused by different processes, such as heating,
cooling, and weathering. The sequence of changes
is called the rock cycle.

Cooling
When melted rock
cools and hardens, it
forms igneous rock.
This can happen after
a volcanic eruption
or underground.

Igneous
rock

Uplift
Metamorphic rock
is forced upward
slowly by pressure
and the movement
of Earth’s crust to
form mountains.

Heat and pressure Metamorphic
Some sedimentary rock rock
is dragged down into the
Melting Earth’s mantle, where
In the heat, some pressure and heat
rocks melt into liquid, changes the rock into
called magma. Pressure can metamorphic rock.
force magma out of the ground.

46

Types of rocks Igneous rock Sedimentary rock Metamorphic rock
Types of igneous rock Types of sedimentary Types of metamorphic
There are three different include basalt (shown rock include sandstone rock include marble
groups of rocks: igneous, here) and granite. (shown here), chalk, and (shown here), slate, and
sedimentary, and These are formed by limestone. These form in shale. These are formed
metamorphic. Types of volcanic eruptions. layers of tiny rock pieces. by heat and pressure.
rocks are classified into
these three different
groups, depending on
how they were formed.

Weathering Rocks on the move
and erosion
Rocks on the surface are Movements in the Earth’s crust are causing rocks to
broken down into smaller slowly change. Volcanoes erupt and mountains are
pieces by weathering. pushed upward, and the rocks that come to the
Erosion breaks down surface are broken down by weathering. This rock is
the rocks further. moved and dragged down into the Earth’s crust again.

Transportation Sedimentation
and deposition and cementation
Pieces of broken rock, called In lakes and oceans,
sediment, are moved along by layers of broken
wind or water, and eventually rock, dead plants,
end up in lakes and oceans. and animal remains
build up and stick
together. This makes
sedimentary rock.

Sedimentary
rock

47

Match up the rocks and minerals with their uses! B Beaded
necklace
Rock uses

Rocks and minerals make up much of our
planet. They are formed deep inside the
Earth over millions of years. Rocks exist
in lots of different shapes, textures, and
colors. They are mined to provide many
of the things around us. Can you guess
which rock is used where?

A Steel nuts
and bolts

Iron ore

Ores are rocks in Earth’s
crust that contain metal.
Iron is strong and hard,
yet easy to work. It
is often turned
into steel.

1 2
Granite
Granite is formed
deep inside Earth’s
crust, when magma
cools down slowly.
It is a tough rock,
used in buildings
and other large
structures.

48