wonders content reader grade 6

Students know evidence of plate tectonics is derived from the fit of the continents; the location of earthquakes, volcanoes, and midocean ridges; and the distribution of fossils, rock

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Grade 6

B

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English Language Development

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Plate Tectonics and Earth’s Structure

1 Plate tectonics accounts for important features of Earth’s surface and

major geologic events As a basis for understanding this concept:

a Students know evidence of plate tectonics is derived from the

fit of the continents; the location of earthquakes, volcanoes,

and midocean ridges; and the distribution of fossils, rock types,

and ancient climatic zones.

b Students know Earth is composed of several layers: a cold, brittle

lithosphere; a hot, convecting mantle; and a dense, metallic core.

c Students know lithospheric plates the size of continents and

oceans move at rates of centimeters per year in response to

movements in the mantle.

d Students know that earthquakes are sudden motions along

breaks in the crust called faults and that volcanoes and fissures

are locations where magma reaches the surface.

e Students know major geologic events, such as earthquakes,

volcanic eruptions, and mountain building, result from plate

motions.

f Students know how to explain major features of California

geology (including mountains, faults, volcanoes) in terms of

plate tectonics.

g Students know how to determine the epicenter of an

earthquake and know that the effects of an earthquake on any

region vary, depending on the size of the earthquake, the

distance of the region from the epicenter, the local geology,

and the type of construction in the region.

Shaping Earth’s Surface

2 Topography is reshaped by the weathering of rock and soil and by

the transportation and deposition of sediment As a basis for

understanding this concept:

a Students know water running downhill is the dominant process

in shaping the landscape, including California’s landscape.

b Students know rivers and streams are dynamic systems that

erode, transport sediment, change course, and flood their

banks in natural and recurring patterns.

c Students know beaches are dynamic systems in which the sand

is supplied by rivers and moved along the coast by the action

of waves.

d Students know earthquakes, volcanic eruptions, landslides, and

floods change human and wildlife habitats.

Heat (Thermal Energy) (Physical Sciences)

3 Heat moves in a predictable flow from warmer objects to cooler

objects until all the objects are at the same temperature As a basis

for understanding this concept:

a Students know energy can be carried from one place to

another by heat flow or by waves, including water, light and

sound waves, or by moving objects.

b Students know that when fuel is consumed, most of the energy

released becomes heat energy.

c Students know heat flows in solids by conduction (which

involves no flow of matter) and in fluids by conduction and by

convection (which involves flow of matter).

d Students know heat energy is also transferred between objects

by radiation (radiation can travel through space).

Energy in the Earth’s System

4 Many phenomena on Earth’s surface are affected by the transfer of

energy through radiation and convection currents As a basis for understanding this concept:

a Students know the sun is the major source of energy for

phenomena on Earth’s surface; it powers winds, ocean currents, and the water cycle.

b Students know solar energy reaches Earth through radiation,

mostly in the form of visible light.

c Students know heat from Earth’s interior reaches the surface

primarily through convection.

d Students know convection currents distribute heat in the

atmosphere and oceans.

e Students know differences in pressure, heat, air movement,

and humidity result in changes of weather.

Ecology (Life Sciences)

5 Organisms in ecosystems exchange energy and nutrients among

themselves and with the environment As a basis for understanding this concept:

a Students know energy entering ecosystems as sunlight is

transferred by producers into chemical energy through photosynthesis and then from organism to organism through food webs.

b Students know matter is transferred over time from one

organism to others in the food web and between organisms and the physical environment.

c Students know populations of organisms can be categorized

by the functions they serve in an ecosystem.

d Students know different kinds of organisms may play similar

ecological roles in similar biomes.

e Students know the number and types of organisms an

ecosystem can support depends on the resources available and

on abiotic factors, such as quantities of light and water, a range

of temperatures, and soil composition.

Resources

6 Sources of energy and materials differ in amounts, distribution,

usefulness, and the time required for their formation As a basis for understanding this concept:

a Students know the utility of energy sources is determined by

factors that are involved in converting these sources to useful forms and the consequences of the conversion process.

b Students know different natural energy and material resources,

including air, soil, rocks, minerals, petroleum, fresh water, wildlife, and forests, and know how to classify them as renewable or nonrenewable.

c Students know the natural origin of the materials used to make

common objects.

Science

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ES 6.1.a

ES 6.1.b

ES 6.1.c

ES 6.1.d

ES 6.1.e

ES 6.1.f

ES 6.1.g

ES 6.2.a

ES 6.2.b

ES 6.2.c

ES 6.2.d

PS 6.3.a

PS 6.3.b

The Forces That Shape Earth 6

A New Quake 8

Description Writing Frame .10

Critical Thinking MAP 1 1 Volcanoes and Earthquakes 12

Kilauea: The Most Active Volcano on Earth 14

Cause/Effect Writing Frame 16

Critical Thinking MAP 17

How Earth’s Forces Shape California 18

The Next Big One 20

Problem/Solution Writing Frame 22

Critical Thinking PHOTOGRAPH/CAPTION 23

Shaping California’s Landscape 24

The Birth of Death Valley 26

Sequence Writing Frame 28

How Sand Builds Beaches 30

Where’s the Beach? 32

Critical Thinking DIAGRAM/ARROWS 35

Natural Disasters Affect Habitats 36

When the Floods Come 38

Cause/Effect Writing Frame .40

Critical Thinking PHOTOGRAPH/CAPTION .41

Heating Things Up 42

Welcome to the City of the Future 44

Critical Thinking DIAGRAM 47

Full of Energy 48

How to Make Ice 50

Contents

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PS 6.4.a

PS 6.4.b

Earth Runs on Solar Power 54

Who Is this El Niño Anyway? 56

Description Writing Frame 58

PS 6.4.c PS 6.4.d Convection Currents Warm the Planet 60

All Steamed Up 62

Compare/Contrast Writing Frame 64

Critical Thinking MAP/LABELS .65

PS 6.4.e The Sun’s Energy Affects the Weather 66

Why the West Is Burning 68

Critical Thinking CHART 7 1 LS 6.5.a Producers, Consumers, Decomposers 72

Ecosystems in a Jar 74

LS 6.5.b LS 6.5.c Food Chains and Consumers 78

Living with the Desert 80

LS 6.5.d LS 6.5.e Biotic and Abiotic Factors 84

Our Packed Planet 86

Critical Thinking CHART 89

LS 6.6.a LS 6.6.b LS 6.6.c Energy Conversions and Natural Resources 90

Green-Fuel Guide 92

Compare/Contrast Writing Frame 94

3

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HSS 6.1.1

HSS 6.1.2

HSS 6.1.3

HSS 6.2.1

HSS 6.2.2

HSS 6.2.9

HSS 6.2.3

HSS 6.2.4

HSS 6.2.5

HSS 6.2.6

HSS 6.2.7

HSS 6.2.8

HSS 6.3.1

HSS 6.3.2

HSS 6.3.3

HSS 6.3.4

HSS 6.3.5

HSS 6.4.1

HSS 6.4.2

HSS 6.4.3

HSS 6.4.4

HSS 6.4.8

HSS 6.4.5

The Beginnings of Humanity 96

Save the Cave 98

Critical Thinking PHOTOGRAPH/CAPTION .1 0 1 Civilization Begins 102

A Is for Ancient 104

Critical Thinking CHART .107

The Rise of Egypt 108

A Lost Kingdom 1 1 0 Description Writing Frame 1 1 2 Critical Thinking INSET MAP 1 1 3 The Beginnings of Judaism 1 1 4 The Story of Abraham 1 1 6 Sequence Writing Frame 1 1 8 Critical Thinking TIME LINE 1 1 9 The Kingdom of Israel 120

Morocco’s Disappearing Jewish Community 122

Problem/Solution Writing Frame .124

Critical Thinking CAPTION 125

Ancient Greece 126

Welcome To Greece 128

Compare/Contrast Writing Frame .130

Critical Thinking PHOTOGRAPH/CAPTION 1 3 1 Greek Mythology 132

A New Subway for an Old City 134

Critical Thinking PHOTOGRAPH 137

Sparta, Athens, and the Persian and Peloponnesian Wars 138

Contents

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HSS 6.5.3

HSS 6.5.4

HSS 6.5.5

HSS 6.5.7

HSS 6.5.1

HSS 6.5.2

HSS 6.5.6

HSS 6.6.1

HSS 6.6.2

HSS 6.6.5

HSS 6.6.6

HSS 6.6.7

HSS 6.6.3

HSS 6.6.4

HSS 6.6.8

HSS 6.7.2

HSS 6.7.3

HSS 6.7.4

HSS 6.7.5

HSS 6.7.6

HSS 6.7.7

HSS 6.7.1

HSS 6.7.8

Early Hinduism and Buddhism 144

A Slow Change in India 146

Critical Thinking PHOTOGRAPH/CAPTION .149

Ancient India 150

India Rising 152

Sequence Writing Frame .154

Critical Thinking MAP/SCALE 155

Ancient China 156

Chinese History Mystery 158

Critical Thinking PHYSICAL MAP 1 6 1 Confucius and Lao–Tzu 162

Revolution and Religion in China 164

Critical Thinking ILLUSTRATION 167

Ancient Rome’s Republic 168

Two Caesars of the Roman Empire 170

Critical Thinking CAPTION 173

The Origin of Christianity 174

The Spread of Early Christianity 176

Critical Thinking ILLUSTRATION 179

Important People in Roman History 180

The Treasures of Zeugma 182

Credits 186

5

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The Forces That

Shape Earth

Plate tectonics is the theory that

Earth’s surface is made up of many

hard plates Earth’s surface is also

called the lithosphere At the very top

of the lithosphere is a thin outer layer

called the crust

The plates are called tectonic plates

The tectonic plates are pieces of the

lithosphere They move slowly across

Earth’s mantle The mantle is the thick

layer of rock and melted rock under

Earth’s surface Most plates only move

a few centimeters, or inches, each year

That is about as much as your

fingernails grow each year

It took about 50 years for most

scientists to agree with the idea of

plate tectonics Alfred Wegener was a

German scientist He first thought of

plate tectonics in 1912 He thought that

Earth’s surface changed over time He

saw that Africa and South America

would fit together if they were next to

each other He called his hypothesis, or

idea, continental drift This is the idea

that in the past a large area of land, one

large continent, broke into pieces These

pieces moved over time to where the

continents we know are today

225 million years ago

Motion of Continents

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Wegener gave a lot of reasons for his

idea of continental drift He saw the

same kinds of rocks in Africa and South

America This could mean that these

continents were once together

Other things show that the

continents have also moved to different

climate zones For example, North

America and Antarctica have coal

Coal is formed from decaying tropical

plants near the equator North America

must have moved north from a

tropical region Antarctica must

have moved south

Fossils of some animals and plants have been found in parts of Africa, South America, India, Australia, and Antarctica These animals and plants could not travel across an ocean

However, their fossils have been found

on continents that are now separated by large oceans Maybe the continents they lived on used to be connected

With all of this evidence, it still took many scientists decades to agree with Wegener’s idea that the continents were once joined in one large continent

Fossil

Evidence

The map shows where fossils of animals and plants have been found in the

southern continents The maps on page 6 show how these continents would

once have fit together in a way that explains the distribution of the fossils.

7

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The people of Indonesia had

two earthquakes in less than

three months.

At 11:09 P.M on March 28, 2005,

Earth’s surface moved This

caused a powerful earthquake The

earthquake damaged many small

Indonesian islands As many as 1,300

people died

Most of the damage was on Nias

It is about 75 miles north of the spot

where the earthquake started That

spot is called the epicenter In this

earthquake the epicenter was in the

Indian Ocean

An Earlier Quake

On December 26, 2004, a huge earthquake shook deep in the Indian Ocean The quake made strong waves

of water A wave made this way is called a tsunami The tsunami swept over the coasts of 11 countries About 174,000 people died One hundred thousand were missing

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American Plate

North American Plate

Paciﬁc Plate

African Plate

NORTH AMERICA

SOUTH AMERICA

Earthquake

INDONESIA

Help Is on the Way

Nias was hit very hard Many

buildings were destroyed For

days the island had little water

or electricity A soccer field was

turned into a hospital

Many countries helped

Indonesia Japan sent a medical

team and supplies Singapore sent

food and water Australia sent

medical supplies The United States

also sent help President George W

Bush said, “The people of Indonesia

can know that our government is

ready to assist.” —Andrea Delbanco

Earth’s top layer is called the crust It is made of seven major

pieces The pieces are called tectonic plates They are always

moving They usually move so slowly that we don’t even feel it

The Major Plates

B C D

Earth’s surface is like a big puzzle The puzzle floats on top of a ball made of hot melted rock Look inside Earth to find out why the surface moves

INNER CORE: A ball of solid rock is at the center of Earth

9

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Description Writing Frame

Use the Writing Frame below to orally summarize

“The Forces That Shape Earth.”

A German scientist named Alfred Wegener had the idea of

continental drift He believed that one large continent

People used to believe that Earth’s surface always stayed the

same Wegener thought that the surface of Earth

Wegener saw that the continents of Africa and South America

Wegener gave evidence for his idea For example, he showed that

rocks in parts of Africa and South America

Coal found in Antarctica shows continental drift because coal

comes from

Use the Writing Frame to write the summary on another sheet of

paper Be sure to include bold signal words Keep this as a model

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2 Point to the sentences in “The Forces That Shape Earth” that

tell the speed of moving tectonic plates

3 Find the paragraph in “A New Quake” that explains how a

tsunami is formed

4 What does the map on page 9 tell you about the

tectonic plates? Discuss the map with a partner Maps are drawings of

geographic locations such as a city, state,

or park.

For a list of links and activities that relate to this Science standard,

visit the California Treasures Web site at www.macmillanmh.com to

access the Content Reader resources

Have students view the e-Review “Earth’s Moving Plates.”

In addition, distribute copies of the Translated Concept Summaries

in Spanish, Chinese, Hmong, Khmer, and Vietnamese.

11

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Volcanoes and

Earthquakes

Many things happen where tectonic

plates meet These events can change

Earth’s surface

Tectonic plates can move in different

directions Divergent boundaries are the

places where plates move “away from”

each other When plates move apart,

new crust is formed Magma, or melted

rock, moves up from the mantle and

spreads over the top

Convergent boundaries are the places

where plates move “toward” each other

When plates come together, one plate

usually goes under the other one This is

called subduction This is how many

volcanoes are formed

Strong forces within Earth make

volcanoes One tectonic plate moves

under another The rock in the mantle

melts It becomes magma The melting

rock forms gases These gases get mixed with the magma Magma that is filled with gas rises It is lighter than the solid rock around it

plate

Types of Plate Boundaries

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PACIFIC OCEAN INDIAN

OCEAN ARCTIC OCEAN

Active volcano Major earthquake Plate boundary

The rocks above the magma push

down on it This creates pressure The

pressure builds up until the volcano

erupts As magma reaches the surface,

it becomes lava Lava moves out of the

surface through holes Lava gets hard

and turns into solid rocks The rocks

pile up and build landforms

Another dramatic natural event is

an earthquake The ground shakes

when plates move and change positions

suddenly The shaking happens when

there is movement along a fault

Faults are cracks in the rocks of

Earth’s surface

Movements happen along faults Fault zones are areas where there are many faults Most faults and fault zones are located where tectonic plates come together

Volcanoes and earthquakes are powerful geologic events They happen along tectonic plate boundaries, the places where tectonic plates meet They change the surface of Earth Look at the map on this page to see where most earthquakes and volcanic eruptions happen

Lithospheric Plates Earthquake and Volcano Activity

13

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The state of Hawaii is known for its beautiful beaches,

warm weather, and one very famous volcano.

Hawaii is the 50th U.S state It is the

only state that is not on continental

North America It is the only state that is

a chain of islands A chain of volcanoes

erupted millions of years ago Hawaii’s

eight main islands are part of this chain

Today the island of Hawaii has two active

volcanoes, Mauna Loa and Mount Kilauea

Mount Kilauea has been erupting since

1983 Its lava has added about two square

miles of new land to the island of Hawaii

People used to think Kilauea was part

of Hawaii’s other volcano, Mauna Loa

Scientists now know that Kilauea has

its own magma Magma is melted

rock deep inside Earth Kilauea’s magma

source is more than 37 miles (60 km)

underground Magma that flows from

a volcano is called lava

Jim Sugar/Corbis

↑ Lava from Kilauea explodes into the

air and ﬂ ows down the sides of the mountain.

Active Volcano on Earth

Doug Cheeseman/Peter Arnold

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Hawaii’s Hot Spot

Hawaii’s volcanic islands are in the middle

of the Pacific Plate They are not on a

boundary between two plates So how

did Hawaii’s volcanoes form? Hawaii is

located over a very hot part of Earth’s

mantle, a hot spot At hot spots, magma

erupts through the plate Over time,

underwater volcanoes build up and up

When they rise above the ocean, they

become islands

The Pacific Plate is the largest, fastest

plate It moves about 4 inches (10 cm) a

year Over time, the plate has moved across

the hot spot Over millions of years, magma

from the hot spot under the Pacific Plate made

the Hawaiian islands —Susan Moger

Angela King/Geology.com

How Old Are These Hawaiian Islands?

Oahu Between 1 million and 5 million years inactiveMaui Between 1 million and 5 million years inactiveHawaii Youngest, 1 million years activeLo’ihi Forming, will probably surface in 10,000 years active

Keeping Up with Kilauea

Every day scientists in Hawaii give information about volcanic activity on Kilauea

You can keep up with Kilauea online at http://hvo.wr.usgs.gov/kilauea/

↑ Hawaii’s islands are the tops

of underwater volcanoes

15

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Cause/Effect Writing Frame

“Volcanoes and Earthquakes.”

Several things cause volcanoes and earthquakes

One reason these events occur is

For all of these reasons, volcanoes and earthquakes are powerful

geologic events They change the surface of Earth

Use the frame to write the summary on another sheet of paper

Be sure to include the bold signal words Keep this as a model of

this Text Structure

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2 Find the paragraph in “Volcanoes and Earthquakes” that explains

how earthquakes occur

3 Point to the sentence in “Kilauea: The Most Active Volcano on

Earth” that summarizes how Hawaii’s volcanoes formed

4 What do the maps on page 13 tell you?

How do the symbols, labels, and keys help

you understand more about this topic?

Maps may include labels that identify cities, states, rivers, or other land features.

Have students view the Science in Motion Video “Plate Movement.”

In addition, distribute copies of the Translated Concept Summaries in

Spanish, Chinese, Hmong, Khmer, and Vietnamese.

17

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How Earth’s Forces

Shape California

California is on two tectonic plates

These plates make up Earth’s surface

Most of California is on the North

American Plate This plate includes

all of North America and part of the

Atlantic Ocean A small part of

California is on the Pacific Plate The

Pacific Plate includes the Pacific Ocean

and a thin piece of California The

North American Plate and the Pacific

Plate slide past each other

The sliding happens along a deep

crack in Earth’s crust called the San

Andreas Fault The San Andreas Fault

begins north of San Francisco It runs about 1,300 km (800 mi) south into Mexico and the Gulf of California The Pacific Plate is slowly moving northwest along the fault It moves at about 5 cm (2 in.) per year Sometimes, the Pacific Plate does not move at all for years Then, suddenly, the rocks on both sides of the fault move as much as several meters (yards) apart

↓ The San Andreas fault line is where the Pacific Plate and the North American Plate meet.

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San Andreas Fault Zone

Over time, the Pacific Plate

pushed into the North American

Plate This made many landforms

now in California

The moving plates made many

of California’s mountain ranges

California’s Coast Ranges are low

ridges that rise up next to the sea

The ridges are made up of layers of

rock This rock has been lifted and

folded into mountains California’s

highest mountains, the Sierra Nevada,

were formed when a large section of

rock was lifted up and tilted

The high mountains of the Cascade Range are volcanic mountains They were made by the moving plates Two famous volcanic mountains are part of Lassen Volcanic National Park Mount Shasta last erupted in 1786 Lassen Peak last erupted in 1921

19

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On April 18, 1906, San Francisco was

“asleep” at about 4:00 AM However,

under the Pacific Ocean a few miles away,

Earth’s crust was breaking like an eggshell

It caused an earthquake, one of the biggest

disasters in U.S history

Buildings fell, clocks stopped, water

pipes broke, gas lines broke, electrical

wires broke Then came fire It burned out

of control for three days

The earthquake and fire destroyed

28,000 buildings This killed more than

3,000 people About 225,000 people lost

their homes

In 1906, no one knew how to tell when

an earthquake was coming Might another quake happen tomorrow?

Learning About a Fault

Scientists learned that a fault line runs along the California coast for about

800 miles They named it the San Andreas Fault

Faults are places where two huge tectonic plates come together The plates move very slowly As they come together, one may slide under or past the other Stress builds up The stress can overcome the strength of the rocks along the fault This causes an earthquake

In 1906, the San Andreas Fault snapped like a rubber band Scientists knew that this could happen again There would be another earthquake But, when?

Police and the National Guard patrol San Francisco after the earthquake of 1906

Humans can’t stop

earthquakes, but we

can get ready.

Many of the buildings in San Francisco

were brought to the ground by the

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Preparing for the Next Big One

Today, scientists understand how tectonic plates

move They know that two plates are moving under

the San Andreas Fault and nearby Hayward Fault

Scientists also know that the San Andreas Fault

may break apart again As for the Hayward Fault,

it “is locked and loaded,” says scientist Thomas

Brocher, “and it could fire at any time.”

Scientists have a computer model of Earth’s

crust in the San Francisco Bay Area They try out

different earthquakes to see what might happen

Even though the 1906 earthquake was very big, an

earthquake right in the middle of San Francisco would be even

worse This would bring hot lava right into downtown

Will the Bay Be Prepared?

Scientists are working to teach people about earthquakes Will

people in the Bay Area listen?

The people of San Francisco have taken some

important steps They have improved the San

Francisco-Oakland Bay Bridge However, they need to do more

There are many old buildings in the Bay Area In an

earthquake, these buildings are likely to fall

Today, the number of people in the Bay Area keeps

growing About 7 million people live there They need to

learn about and prepare for earthquakes Scientists say the

Bay Area will soon have more earthquakes This could lead

to a quake as strong as the one in 1906.—J Madeleine Nash

↑ Beyond the San Francisco-Oakland Bay Bridge,

skyscrapers rise

in San Francisco today

↑ In 1989, an earthquake caused part of the San Francisco-Oakland Bay Bridge to fall

AP Photo

Matthias Kulka/Corbis

21

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Problem/Solution Writing Frame

“The Next Big One.”

Earth’s forces threaten California with earthquakes, like the

terrible San Francisco quake of 1906

The 1906 quake occurred because

this Text Structure

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Critical Thinking

1 Most of California rests on the

A Pacific Plate

B San Andreas Fault

C North American Plate

2 Which words in “How Earth’s Forces Shape California” name

a deep crack in Earth’s crust in California?

3 Point to the place in the text in “The Next Big One”

that tells you about how earthquakes happen

4 Look at the photo on page 18 Discuss with a

partner how the caption helps you understand

the text

Photographs and captions help you understand an informational article.

Have students view the e-Review “How Plate Tectonics Affect

California.”

In addition, distribute copies of the Translated Concept Summaries

in Spanish, Chinese, Hmong, Khmer, and Vietnamese.

23

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Shaping California’s Landscape

California has many rich valleys The Central Valley is

an area of low land The Sierra Nevada is to the east and the Coast Ranges are to the west Deep layers of rock have come down from the mountains around the valley This rock makes up the valley floor It is the largest valley

in California It covers about one sixth of the state

The Los Angeles Basin is a

low-lying area between the

Transverse and the Peninsular

Ranges The basin is filled with

rock material This rock has come

down from these mountains The

Ventura Basin is in the Transverse

Ranges Thick layers of rock

materials have collected there

Tree roots can get into cracks

in rock In time the rock may

break apart →

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California’s valleys and basins

are formed through the process of

weathering Weathering is the slow

breakdown of rock into smaller pieces

Rain and snow, wind, plants, and

temperature change can all break rocks

into smaller pieces

These smaller pieces of rock—and

soil—are then carried away by gravity,

wind, ice, and water They can be

dropped off in new places Erosion is

the carrying away of smaller pieces of

rock and soil Deposition is dropping

off of the soil and rock in new places

Weathering, erosion, and deposition

together reshape the land

Water is the biggest reason the

landscape of California and the rest of

the world changes After falling as rain

or snow, water moves downhill because

of gravity The flowing water washes

away sand and soil It moves boulders

It cuts through rock It then leaves these

materials in new places Flowing water

in streams and rivers changes the Earth’s

surface Over millions of years, the

moving waters can cut through

solid rock

A waterfall in Yellowstone National Park →

25

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What’s in a Name?

During the Gold Rush (1849), a group

of pioneers tried to take a shortcut to

California The trip was very hard and

took many months Only one person

died, but the “shortcut” was called

Death Valley

How It BeganAbout 1.3 billion years ago the floor

of Death Valley was covered in mud Then, water washed over the mud

Ocean plants grew over the sea bottom The land rose up above the sea Then the land was worn down again by erosion This happened over and over again

The name sounds scary, but Death Valley is really a beautiful park

It is the lowest spot in the United States (282 feet below sea level)

It is also the driest In summer, temperatures in Death Valley can go

above 120 degrees Fahrenheit At other times, floods are a danger

California’s Death Valley was once filled with water and life.

The Birth

of Death Valley

↓ Pioneers crossed Death Valley during

the California Gold Rush.

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About 550 million years ago, Death

Valley was a shallow sea 100 miles

wide It was home to many plants and

animals

Crashing Mountains

Then around 225 million years ago,

two tectonic plates—large,

slow-moving parts of Earth’s crust—crashed

together The quiet sea turned into

erupting volcanoes Mountains and

valleys formed west of Death Valley

Later—about 30 million years ago—

the plates pulled apart Mountains and

valleys formed in Death Valley Rocks

piled on top of each other Then they

fell and crashed to form new mountains

and hills

Ice Age and

Lake Manly

Then the Ice Age came to Death

Valley Mountains of ice, called

glaciers, grew Rivers flowed This

formed a huge lake called Lake Manly

Slowly, Lake Manly was cut off from

the melting glaciers of the Sierra

Nevada The lake evaporated The

water disappeared In 2005 the Lake

Manly basin flooded again Suddenly, people were able to boat across Death Valley! But the lake was only about two feet deep It quickly evaporated

Death Valley changed over millions

of years It is still changing —Lisa Jo Rudy

↑ Rock formations tell the story of Death

Valley’s watery past.

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Sequence Writing Frame

“The Birth of Death Valley.”

California’s Death Valley is a beautiful park with interesting land

formations About 1.3 billion years ago the area began as a

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2 Find the sentence in “Shaping California’s Landscape” that

tells what happens during deposition

3 Point out the paragraph in “Shaping California’s Landscape”

that discusses the importance of water

4 How does the photograph at the bottom of

page 24 help you understand the text? Photographs and

captions help you understand an informational article.

access the Content Readers resources

Have students view the e-Review “Weathering, Erosion, and

Deposition.”

Spanish, Chinese, Hmong, Khmer, and Vietnamese

29

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How Sand

Builds Beaches

Sand is made a few pieces at a time

It is made when rocks or other materials

are broken down into small bits by

weathering On North America, most of

the sand on ocean beaches comes from

the land Rivers carry small pieces of

rock long distances These small pieces

of rock are called sediment When the

river gets to the ocean, it deposits some

of the sediment at the river’s end Wind and water carry the small pieces into the ocean and along the beach

Ocean waves come in to shore and then back out to sea The waves change

the shape of the coast Beach erosion

happens when waves pick up sand and move it along the shore The waves can make a shoreline that is smooth or a shoreline that is rough

British West Indies

direction of drift

currentpath of sand particles

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In many places, beach drift occurs

Beach drift happens when sand is pulled

along a beach Ocean waves come in to

shore at an angle Breakers are waves

that break into foam or bubbles at the

shore Breakers go back into the ocean

at another angle This causes a zigzag

movement of sand down the beach as

much as hundreds of meters a day

The movement of sediment along

the shore depends on the currents, the

size of the sand grains, and the waves A

current is the flow of a part of a body of

water in a given path

A large amount of sediment can

be moved along a beach Sometimes sand can build up The sand can build different land formations, such as sandbars

A sandbar is an area where waves drop off sand and where shallow water collects Sandbars form away from shore They can be a few meters wide to hundreds of kilometers wide Sandbars more than 100 meters (328 feet) wide are called barrier islands

This sailboat hit a sandbar near Oxnard, California

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Beach erosion can be caused by

nature and by humans.

Disappearing Beaches

Everyone loves a day at the beach and

California is famous for its beaches

However, each year, many California

beaches lose sand Some beaches

almost disappear

Beaches are the best way to keep

the Pacific Ocean away from cities and

towns When waves hit beaches, they

are very powerful As the waves make

their way up the beach, they get

smaller If strong ocean waves hit

cities, the buildings wouldn’t last long

Where Did the Beaches Go?

Sometimes losing sandy beaches

is natural Storms carry sand away Water moves sand from place to place Often, though, people cause beach erosion—the loss of beach sand and dunes Sometimes things we do to try

to help beaches cause problems Sea walls hold the ocean back from our streets, but they also stop beaches from growing Eventually beaches can disappear

Groins are walls that are built into the ocean at right angles to the beach They are supposed to stop sand from washing away Groins do work

However, they also can harm beaches

up the shoreline Groins separate those beaches from the water that carries sand to them

David McNew/Getty Images

Erosion comes close

Santa Monica, California

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Dams on rivers can also harm

beaches Dams stop river sand from

flowing to the ocean where it helps

build beaches Harbors and marinas

also prevent sand from being carried

to beaches

Saving the Sand

Some communities have taken down

groins and seawalls Some plant sea

grass to hold sand in place Some

communities have brought in sand

from the ocean floor

A Merry, Merry Beach

Some communities are trying to build

sand dunes Sand dunes are tall hills

of sand held in place by plants like

beach grass Dunes protect the land

from waves They also help hold sand

These houses are

being lost to erosion.

These Christmas trees will help protect the beach at Surfside Beach, Texas.

Sand dunes can form naturally However, some communities are helping by using Christmas trees!

After Christmas, towns collect the trees and bring them to the beach The trees are placed on their sides along the beach The trees’ thin needles catch and hold sand

Eventually the trees and sand form dunes that can last —Lisa Jo Rudy

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Cause/Effect Writing Frame

“How Sand Builds Beaches.”

Rivers carry and deposit sediment to the ocean One effect of

Breakers come in at one angle and go back into the ocean at

another This causes sand to

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Critical Thinking

1 Waves that break into foam, or bubbles, when they hit the

beach are called

A breakers

B beach drift

C sandbars

2 Point to the sentence in “How Sand Builds Beaches” that

explains what beach erosion is

3 Find the paragraphs in “Where’s the Beach?” that tell

how people can cause beach erosion

4 Study the diagram on page 30 Discuss

with a partner what affects the shoreline Pay attention to the

arrows on the process diagram They show the direction in which something moves.

visit the California Treasures Web site at www.macmillanmh.com

to access the Content Readers resources

Have students view the e-Review “Beach and Wave Erosion.”

Spanish, Chinese, Hmong, Khmer, and Vietnamese

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↓ Destruction caused by the eruption of Lassen Peak

↑ Lassen Peak erupted early

in the twentieth century

It is still an active volcano.

Natural Disasters

Affect Habitats

Natural disasters can cause violent changes to

Earth’s surface An earthquake can open large

cracks in the ground A landslide landslide can bury land

under rocks and mud A river can flood a large

area with water and sediment A volcano can

cover an area with hot lava and ashes

These changes can have long-term effects on

habitats When a habitat is damaged, the plants

and animals there may be harmed They may lose

their homes They may not be able to find food

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For example, Lassen Peak, an active volcano in California, erupted in

May 1915 Before 1915, trees covered the side of the mountain Hot gases, ash, and rock from the eruption broke and burned the trees and other plants This area was called the Devastated Area Today, new trees hide the damage

Earthquakes bring destruction An earthquake occurs when plates, pieces of Earth’s surface, move suddenly The ground shakes In October 1989 an earthquake hit California It caused major damage to the San Francisco Bay Area The shaking caused the upper level of a freeway to collapse into the lower level.When an earthquake occurs in a city, electric and gas lines are often broken The broken lines cause fires The shaking damages buildings, highways, and other structures Some earthquakes open huge cracks in the ground

A landslide can cause even more damage A landslide is the fast movement

of rock, soil, and debris down a hill A landslide can carry buildings down a hillside It may rip trees and plants from the ground It can change a small slope to

a steep cliff Falling rocks and soil can dam up a river or stream This could change the course of the water, or cause a flood Falling rocks may damage the bottom of the river They can pull up plants and kill fish and other animals

↑ Gravity and a steep hill caused this

landslide near La Conchita, California.

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P eople have had floods throughout

history Now, with the possibility of

climate changes, flood protections that

worked in the past may no longer help

How Climate Change

May Cause Floods

As Earth warms, weather changes

More powerful storms are probable In

some places, there may be more rain

Melting ice sheets may cause sea levels

to rise This would put areas on the

coast in danger of flooding

Until now, most countries have built

dikes and levees to protect against

floods Dikes and levees are walls that

People adapt to flooding.

hold back rising waters But levees did not protect New Orleans after Hurricane Katrina Planners now know

we need more

Staying Dry

London, England, is a city with a history

of floods In 1983 the Thames Barrier went into operation It is a system of huge barriers with floodgates The gates close when the Thames River gets too high The English thought they would close the gates about once a year Instead, they’re now closing them ten times a year!

Gideon Mendel/Corbis

When the Floods Come

← In June 2007, northern England had a freak tropical storm, flooding many towns People had to leave their homes.

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In Holland, the Dutch have plans to

allow certain areas to flood This will

protect big cities from flooding

Japan is an island country Japan

faces the threat of rising sea levels

In Tokyo the city has built an

underground channel This channel

can drain flood waters that threaten

the city

How Can We Adapt to

More Flooding?

Scientists say rebuilding levees isn’t

enough They say we need to restore

wetlands, too Wetlands act like

natural sponges They soak up flood

water Around New Orleans, many

natural wetlands have been destroyed

Land was used for housing or drilling

Barrier islands are also a form of

flood protection Barrier islands stand

between the ocean and the land They

help reduce flooding caused by storms

and rising ocean levels

Scientists, leaders, and ordinary

people are working to protect us from

the threat of flooding —Lisa Jo Rudy

↑ In the Netherlands, dikes like this one have been the main ﬂ ood protection.

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