A R C T I C C I R C L E

E Q U ATO R

T R O P I C O F C A N C E R

T R O P I C O F C A P R I C O R N

L.Titicaca

Great BearL.

Great SlaveL.

GreatLakes

São

Fran

cisco

Amazon

Missouri

Mis

siss

ippi

Rio GrandeYukon Mackenzie

Para

ná

AN

DE

S

AN

DE

S

APPALACHIA

NM

TS.

COA

STR

AN

GES

COAST

MTS.

RO

CK

YM

OU

NT

AIN

S

H u d s o nB a y

B a f f i nB a y

DavisStrai tBeri

ngSt

rait

G u l f o fM e x i c o

G u l f o f A l a s k a

CapeHorn

MidwayIs.

Marshall Is.

Aleutian Is.

Hawaiian Is.

Loyalty Is .Van

uatu

BountyIs.

AntipodesIs .

A u c k l a n dI s .

TungaruTuvalu

Fi j i

MarquesasIs.

TubuaiIs.

TahitiSociety Is.

Samoa

Ton

ga

ChathamIs.

PhoenixIs.

Tuamotu Is.

Cook Is.

L i n eI s .

N e wZ e a l a n d

J u a nF e r n á n d e z

I s .

FalklandIs.

GalápagosIs.

Newfoundland

Bermuda

Azores

Greater Anti l les

Bahamas

G r e e n l a n dMelvil le

I. DevonI.

E l l es m e r e I .

Banks I.V i c t o r i a I .

B a f f i nI .

Lesser Antill

es

(Gi lber t Is .)

A T L A N T I C

O C E A N

P A C I F I C

O C E A N

A T L A N T I C

O C E A N

C H U K C H IS E A

B E R I N GS E A LABRADOR

SEA

GR

EEN

LA

ND

SEA

E A S TS I B E R I A N

S E AB E A U F O R T

S E A

C A R I B B E A NS E A

A M A Z O N B A S I N

LL

AN

OS

PLATEAU OFMATO

GROSSO

AT

AC

AM

AD

ESE

RT

P A M P AS

PA

TA

GO

NI A

SIERRAM

ADRE

S O N O R A ND E S E R T

GREATPLA

INS

N O R T H

A M E R I C A

S O U T HA M E R I C A

C E N T R A L

A M E R I C A

EQUATOR

TROPIC OF CANCER

ARCTIC CIRCLE

THINGS TO LOOK FOR ON THE MAP

Highest point on Earth: Mt. Everest,China/Nepal, 29,035 ft (8,850 m)Map H6Lowest point on Earth: MarianaTrench, Pacific Ocean, 35,840 ft(10,924 m) below sea level Map L8Longest river: Nile, Egypt/Sudan/Uganda, 4,187 miles (6,738 km) Map E7Largest lake: Caspian Sea,Azerbaijan/Iran/Turkmenistan/Kazakhstan/Russian Federation,146,101 sq miles (378,400 sq km)Map F5Largest ocean: Pacific Ocean,63,804,540 sq miles (165,241,000 sq km) Map Q7

CONTINENTSThe seven continents that make up

the world’s land mass are, fromlargest to smallest: Asia, Africa,North America, South America,Antarctica, Europe, and Australia.The polar regions, not completelyvisible on the flat map, surroundthe North and South poles and are

shown on the globes left and below.

Only 29 percent ofthe Earth’s surfaceis land. Thepercentage area ofeach continent isshown here.

Water: 71%

Land: 29%

Asia: 30%

Africa: 20%

NorthAmerica:16.5%

SouthAmerica:

12%

Antarctica:9.5%

Europe:7%

Australia:5%

1

2

3

4

5

6

7

8

9

10

11

12

13

U V W X Y A

Earth’s surface

THE PHYSICAL WORLD

N O P Q R S T

12

MID

-ATLANTIC

RID

GE

EA

ST P

AC

IFIC

RIS

E

PACIFIC-ANTARCTIC RIDGE

SOUTHEAST INDIAN RIDGE

SOUTHWEST INDIA

N RID

GE

MID-I ND

IAN

RID

GEMID

-ATL

AN

TIC

RID

GE

PHILIPPINE PLATE

I N D O - A U S T R A L I A N P L A T E

ARABIAN PLATE

IRANIAN PLATE

A N T A R C T I C P L A T E

A F R I C A N P L A T E

E U R A S I A N P L A T E

P A C I F I C

P L A T ECOCOS PLATE

CARIBBEAN PLATE

NAZCA PLATE

SCOTIA PLATE

S O U T H A M E R I C A N

P L A T E

N O R T H A M E R I C A N

P L A T EJUAN

DE FUCA PLATE

Subduction zoneMid-ocean ridge and faultsCollision zoneUncertain plate boundary

Movementof plate

Volcano

KEY TO MAP

MOVING CONTINENTS

MOVING CONTINENTSTHE CONTINENTS THAT MAKE UP most of the Earth’s land surfaceare always on the move, shifted around by forces deep inside theEarth. This is known as continental drift. Movement, or drift,takes place because of intense heat generated within the Earth.The heat is carried upward where it disturbs the cool, rockysurface, or crust, forcing sections of it, called plates, to move.Each year the continents, parts of the plates, drift nearly half an inch (about a centimeter), some getting closer together, others moving farther apart, some grinding past each other. As this happens, many of the Earth’s natural features are created or changed. INSIDE THE EARTH

The Earth is not a solid ball, but is made up of many different layers. The crust that formsthe continents and the ocean floors is a thinlayer of rock that covers the Earth like a shell.The mantle beneath is 1,864 miles (3,000 km)thick and made of hot rock, some of which ismolten (liquid). At the center is the core, thehot metallic center of the Earth. This is liquid

on the outside and solid on the inside.

IN THE BEGINNINGScientists believe that some300 million years ago all theland on Earth was joined togetherin one “supercontinent” called Pangaea. Itwas surrounded by a giant ocean, Panthalassa. About200 million years ago, as the plates moved, Pangaeabegan to split into two great landmasses, Laurasia inthe north, and Gondwanaland in the south. These wereseparated by the Tethys Sea. As the plates continued tomove, the two landmasses split and moved farther apart,eventually forming the continents on the map below.

Liquidouter core

The hotinner coreis solid

Earth’s crust

Upper mantle

200 million years ago

180 million years ago

65 million years ago

P ANTHALA SSA

TE THYS SE ANORTH

AMERICA

Lowermantle

PA N T H A L A S S A

SOUTHAMERICA

EUROPEASIA

AFRICA

AUSTRALIA

ANTARCTICA

PA

NG

AE

A

L AU R A S I A

GO

N D WA N A L A N DINDIA

The Earth Inside and Out 29

Places & TermsIdentify and explainwhere on the earththese terms would befound.

• continent

• mantle

• magma

• crust

• biosphere

MAKING COMPARISONS Study the diagrams of continental drift on this page. Write a description of the location of the continents in the past in comparison with their current location.

Taking Notes PLACE Review the notes you tookfor this section.

• What are the three basic parts ofthe earth’s interior?

• What are four basic spheresfound on or above the earth?

Main Ideas a. What makes up the

interior of the earth?

b. What makes up thebiosphere?

c. How can the presence of seven continents on the earth’s surface beexplained?

Geographic ThinkingMaking Inferences How dothe earth’s spheres influenceone another? Think about:

• the function of theatmosphere

• the makeup of thebiosphere

See SkillbuilderHandbook, page R4.

CONTINENTAL DRIFT In 1912,Alfred Wegener of Germany presented a new idea about continents—the continental drifthypothesis. It maintained that theearth was once a supercontinentthat divided and slowly driftedapart over millions of years.Wegener called the supercontinentPangaea (from a Greek word mean-ing “all earth”). An ocean calledPanthalassa surrounded it. Thesupercontinent split into manyplates that drifted, crashed intoeach other, and split apart severaltimes before they came to their cur-rent positions. This processoccurred over millions of years.

In the 1960s, scientists study-ing the sea floor discovered thatthe youngest rocks were in themiddle of the ocean, at longcracks in the crust. This suggestedthat the new sea floor was beingadded, pushing the continentsapart. Later in this chapter, youwill learn how the rocks of Earth’ssurface are broken into giantplates that move and continue toshape the earth.

LivingPlanet

EarthInside & Out

PA

N

GA

EA

TethysSea

PANTHALASSAOCEAN

200 million y

NORTHAMERICA A S I A

AFRICASOUTH

AMERICA INDIA

AUSTRALIA

ANTARCTICA

65 million years ago

AmericanPlate

PacificPlate

PacificPlate

EurasianPlate

AfricanPlate Indo-

AustralianPlate

Antarctic Plate

ANTA

ANTARCTICA

NORTHAMERICA A S I A

AFRICA

SOUTH AMERICA

AUSTRALIA

EUROPE

Today

200 million yearsago The super-continent wasnamed Pangaea.An ocean calledPanthalassasurrounded it.

65 million yearsago The super-continent split apartand began movingin different direc-tions. Notice thatIndia broke awayfrom Antarcticaand Australia anddrifted toward Asia.

Today The contin-ents continue todrift even today.