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EARTH'S C RUSTInside the Earth

Information Card #2

People have always wondered what the inside of the earth islike. The ancient Greeks believed it was Hades, the world of thedead. In his famous book, Journey to the Center of the Earth,science fiction writer, Jules Verne, depicted the inside of the earth asa place of great crystal caverns and prehistoric monsters. With all theknowledge scientists have gained about the earth over the years,little is really known about the interior of the earth. Scientists can onlystudy the crust of the earth for clues and theories about what is atthe heart of our planet.

Most of the information geologists have about the inside of the earth has beengained from studying the geologic events that occur on the earth's crust, especiallyearthquakes. Investigating earthquake waves is one of the few ways geologists have oflearning about the inside of the earth.

Earthquakes are caused by sudden shifts of rock on ornear the surface of the earth. These shifts produce waves ofenergy called 'seismic waves', which spread out in manydirections. Seismic waves from an earthquake travel throughthe earth like sound waves travel through the air, and arerecorded with special instruments called seismographs.Seismologists record these waves at different places on theearth's surface, and collect information about groundmovements before, during, and after an earthquake. Aswaves pass through different substances in different ways,scientists are able to make very good guesses about thecomposition of the earth.

Scientists know that various types of earthquake waves travel at different speedsthrough different rocks. They change direction as the pass from one layer to another.The waves travel faster In high-density mantle then they do in the crust, which consists oflighter material. When the waves pass from one material to the other, they bend and arebounced back, depending on the substance they are going through. Seismologistsrecord these waves at different places on the earth's surface. By recording where theshock waves arrived, the angle at which they emerged, and the time it took for them toarrive, scientists have an Idea of the type of material they passed through. By putting alltheir records together and comparing them, scientists are able to learn more about whatis happening inside the earth. By comparing many seismological records, scientists havebeen able to theorize about the composition of the earth's interior. They have an idea ofhow far below the earth's surface each layer is, its thickness, and its composition.

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Cutting into the earth, we would pass through three layers. All the landforms of theearth, such as mountains, hills, valleys, and plains, are part of the first layer, the earth's'crust'. It is the crust which supports all life and from which we obtain many of the

resources we use for survival on our planet. The earth's crust makes up less than 1percent of the earth's volume, and varies in thickness from about 5 km (3 mi) under theoceans, to about 40 km (25 mi) at its greatest depth. If we compared the earth to anapple, the crust of the earth, which makes up our continents and the ocean floors, isthinner than the skin on the apple.

The layer beneath the crust is called the 'mantle' and accounts for approximately83 percent of the earth's volume. The mantle is a thick layer which is about 2 900 km(1 800 ml) deep. The upper part of the mantle is solid like the crust and, along with thecrust, makes up the geological region called the 'lithosphere'. The lower part of themantle has much higher temperatures and pressure. The rock in the lower part of themantle is melted or 'molten', and it is thought that it flows slowly. This molten part of themantle is called the 'asthenosphere'.

The core is even hotter than the mantle and makes up about 16 percent of theearth's volume, and 32 percent of the earth's weight. The core consists of two regions:

-'the 'outer core' and the 'inner core'. The inner core, or center of the earth, is made ofiron and nickel, and because of the extremely high pressure geologists believe it isprobably solid. The inner core is thought to be 2 500 km (1 500 mi) across while the outercore is about 2 200 km (1 300 mi) thick. Because of the high heat, the outer core isthought to be very liquid. Geologists believe the outer core flows very slowly and formsthe magnetic field of the earth.

Research Challenge!Do some research and find out the temperatures of the differentlayers of the earth's interior. You may discover that theinformation in different reference books varies. What reasons canyou think of to explain this?

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OTM-2109 • SSBI-109 Earth 's Crust

EARTH 'S C RUSTWhat is Geology?

Info Check

1. Write definitions for the following words:

0

a) theory:

b) origin:

c) predict:

d) formation:

2. Match each science with the special area studied.

a)

the study of the earth's crust

b)

the study of living things

c)

the study of crystals

d)

the study of earthquakes

e)

the study of the weather

f)

the study of stars and planets

g)

the study of volcanoes

h)

the study of fossils

i)

the study of humankind

j)

the study of minerals

crystallography

seismology

mineralogy

geology

biology

paleontology

anthropology

volcanology

meteorology

astronomy

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EARTH 'S C RUST

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3. Many scientific words come from the ancient Greek and Latin languages. Try tomatch the Greek or Latin words with their meaning. Write three words containingeach prefix.

life

earth

home

heat

stars

a) life

bio -

biology

b) geo -

C)

eco -

d) thermo -

e) astro -

,

4. List aspects of the earth that are of special interest to a geologists.

f)

g)

h)

d) 1) -

e) j) -

5. Explain the importance of the science of geology.

a)

b)

C)

0© On the Mark Press • S&S Learning Materials 18 OTM-2109 • SSBI -109 Earth 's Crust

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DATE NAME: CLASS:

ASSESSMENT

Layers of Earth QuizLBLM 1 1--24

Goal • Use this quiz to assess your knowledge and understanding of the different layers ofEarth and associated concepts.

What to` Do

• Using the following diagram, complete the chart below.

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Layer name State (gas/liquid/solid) Approximate thickness (km)

A

B

C

0

E

580 Copyright 0 McGraw-Hill Ryerson Limited. Permission to reproduce this page is granted to the purchaser for use in her/his classroom only.

0

EARTH 'S C RUST4. Complete the diagram below to illustrate the inside of the earth. Color the diagram

so that each layer is clearly shown.

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Letter Earth Layer Description

crust

upper mantle

lithosphere

asthenosphere

inner core

outer core© On the Mark Press • S&S Learning Materials

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OTM-2109 • SSBI-109 Earth's Crust

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EARTH'S CRUSTEarth Teetonies

information card #3

Geologists know the earth's crust ischanging all the time. It is moved from sideto side and tilted upwards and downwardsby forces from inside the earth. Suddenmovements cause powerful earthquakes toshake the earth and volcanoes to erupt.Islands and mountains are formed whenpressure causes the earth's crust the wrinkle.

Geology theorizes that millions of yearsago the continents were once all joinedtogether as one supercontinent. This theorywas first presented In 1923 by ameteorologist, named Alfred Wegener.Wegener proposed the theory that the continents are constantly moving, drilling overthe surface of the earth. He believed they were once a part of a single supercontinentwhich he named "Pangaea", meaning "all lands". Wegener theorized that about 200million years ago, when the dinosaurs were appearing on the earth, Pangaea started tosplit apart. Slowly, over millions of years, masses of land broke away from Pangaeaforming the continents. The portion holding North America and Eurasia moved north,

and then over millions of years, split in two. The remainder of thesupercontinent split into South America, Africa, Antarctica,Australia, and India. As he studied the coast of South Americaand Africa, he found that the types of rock in each place werevery similar and used this evidence to support his theory. Hisideas, however, were not accepted by the scientific community,and he died in 1930 having gained no support for his theory.

In later years, geologists found similar rock formations onboth sides of the Atlantic Ocean. Rocks found in Brazil, Scotland,Labrador, Madagascar, India, and the Ivory Coast of Africa werealike. Fossils found on both sides of the Atlantic contained the

remains of the same kinds of plants and animals that are now extinct. More importantly,however, was the discovery that the large underwater range of mountains called the'Mid- Atlantic Ridge'. The Mid-Atlantic Ridge is located where large plates are movingaway from one another creating a crack in the ocean floor. This range of mountains isconstantly being built by 'magma' (hot, molten rock from the interior of the earth) which

C pushes itself up through the crack in the ocean floor, spreading the floor in oppositedirections. Scientists then had proof to support Wegener's theory.© On the Mark Press • S&S Learning Materials

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EARTH'S CRUST

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In the 1970s, geologists developed a theory about the movement of the continents.This theory is known as the 'Theory of Plate Tectonics'. 'Tectonics' means building or

construction. Scientists believe that the earth's crust consists of several large and smallplates. Six of these large plates include all or part of a continent and some of itssurrounding water. The tectonic plates all fit together on the surface of the earth likepieces of a giant jigsaw puzzle. These plates are irregular in shape, millions of squarekilometers in area, and 60 to 80 km (40 to 50 mi) thick. Along with a hard upper layer ofthe mantle, they form the lithosphere.

Scientists believe these lithospheric plates float very slowly on the soft, molten layerof the mantle underneath the lithosphere, called the asthenosphere. Many geologiststhink there are strong convection currents in the mantle. These currents are formed fromthe heat given off by the core. They cause the asthenosphere to keep moving. Theplates with continents on them travel about 2 cm (0.75 In) a year. The plates under thewater shift as much as 15 cm (5 in) per year.

Geologists believe the continents have been drifting around the surface of the earthin this manner for billions of years in a process known as 'continental drift', which isresponsible for many of the changes that take place on the surface of the earth. Theplates are constantly moving, sliding past one another, bumping into one another andoverlapping each other. Mountains and volcanoes are formed where the plates collideinto one another and move away from one another, and earthquakes occur as theplates rub against on another.

The Earth's Tectonic Plates

© On the Mark Press • S&S Learning Materials 30 OTM-2109 • SSB1 -109 Earth 's Crust

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12. Match each number on the map with the name of the tectonic plate in the chartbelow.

North American Plate lndo-Australian Plate

African Plate Eurasian Plate

Pacific Plate Arabian Plate

South American Plate Anarctic Plate

13. Explain the Continental Drift Theory.

© On the Mark Press • S&S Learning Materials

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OTM-2109 • SSB1-109 Earth 's Crust

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EARTH 'S CRUSTEarth Tectonics

Info Check

1. Who was Alfred Wegener, and why was he important to thestudy of geology? What was his theory?

2. What made the scientific community accept Wegener's theory years later?

3. What does the word "Pangaea" mean?

4. Explain the term "continental drift".

J!

© On the Mark Press • S&S Learning Materials

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OTM-2109 • SSBI -109 Earth's Crust

Eurasian Plate

North AmericanNorth American PlatePlate

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EARTH 'S C RUST

The Major Tectonic Plates of the World

Phillipines Plate

♦ Direction of movement of the plates

5. a) Which plate does not carry a continent?

b) Which plates are causing the volcanic action around the Iceland?

c) Which plates collided to form the Himalayas?

C.:

d) Which two plates formed the rift valley that the Red Sea now occupies?

© On the Mark Press • S&S Learning Materials

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OTM-2109 • SSB1-109 Earth's Crust

EARTH 'S CRUSTG, 6. Is the Atlantic Ocean getting wider? Explain.

7. Complete the table below by naming the plate and the direction in which it ismoving.

Name of Plate Direction ofMovement

Name of Plate Direction ofMovement

8. The smaller plates are not labeled on the map. Using an atlas, locate the followingplates and label them on your map. If possible, find the direction in which they aremoving.

a) Cocos Plate b) Caribbean Plate

c) Philippines Plate

9. Using the map below draw the Pacific Plate.

© On the Mark Press • S&S Learning Materials

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EARTH 'S CRUST

Name:

Date:

Quiz #11. The study of the earth beneath us is known as the study of

2. The thinnest layer of the earth is the

3. Name the scientist known as 'the founder of modern geology'.

4. The ancient Greek word 'geo' means

5. Most of the knowledge about the interior of the earth has come from studying

6. A paleontologist is a scientist who studies

7. Seismology is the study of

8. The Greek word for 'life' is

9. The lower part of the mantle is called the

10. The densest layer of the earth is the

11. Label the layers of the earth on the diagram below.

© On the Mark Press • S&S Learning Materials

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OTM-2109 • SSBI-109 Earth's Crust

U VI F:

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CHAPTER;x,

The Story of Earth's CrustWord Search

Goal • Use this word search puzzle to apply the scientific vocabulary you learnedin Chapter 12.

What to Do• Find the hidden words in the word search puzzle below.

Hidden Words

VOCABULARY CHECK

CONTINENTAL DRIFTCONVECTIONCURRENTDINOSAURERAGLOSSOPTERISHALF-LIFEHUTTONINDEX FOSSIL

LYELLLYSTROSAURUSMAGNETOMETERSMESOSAURUSMETEOROLOGYMID-ATLANTIC RIDGEMOUNTAINPANGAEAPLATE TECTONICS

PRECAMBRIANRADIOCARBON DATINGSONARSUBMERSIBLESUPERPOSITIONTUZO WILSONUNIFORMITARIANISMWEGENER

Copyright © McGraw-[fill Rversnn Limited. Perttussion to reproduce this page i; granted to the purchaser for issc :m her/his daasroom oniv

621

DATE:

NAME:

CLASS:CHAPTER 12

1BLM 12-25

VOCABULARY CHECK The Story of Earth's CrustWord Search (continued)

B X R Q M L B F V S U R U A S O S E M KY I P M L M N X Z J E C R U A S O N I D

I H J E W D Q Q O N R N M D D O S C D CC A Y V M B Q H E K O Y N V D N T K - WF L M T N R J G W T Q D K A E A G N A PN F C O N V E C T I O N C U R R E N T JA - A Z O W U U S I R E T P O S S O L G

I L N K X B H R T J A I Z K F Q G D A NR I O M S I N A I R A T I M R O F I N UB F I C O N T I N E N T A L D R I F T LM E T E O R O L O G Y W R T M J N N I IA H I L O E P L A T E T E C T O N I C SC P S R M S M M A G N E T O M E T E R SE H O V P F M V S L W Q T D I F B S 1 0R G P I R M B X N K B U H Q F R D S D FP K R A D I O C A R B O N D A T I N G XY S E Y H I X K S U B M E R S I B L E EL G P U D Z R B T G B J T Q T X R W S DM O U N T A I N F F T U Z O W I L S O NL Y S T R O S A U R U S T W B L W M H I

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622 Copyright 0 McGraw-Hill Ryerson Limited. Permission to reproduce this page is granted to the purchaser for use in her/his classroom only.

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Tectonic Plate MovementDescription of Margin:

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