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TitleRocks and Minerals
TagsNatural Materials Earth & Life Sciences Materials Rock (Geology) Rocks
File Size7.3 MB
Total Pages52
Document Text Contents
Page 26

M ETAMORPH I C ROCKS

LIMESTONE

MARBLE

Why do rocks

have different TH E NAME metamorphic
shapes and colors? means "to have
been changed." This name is used to tell
about rocks that have been changed in
some way. This is the third and last big
group of rocks.

Metamorphic rocks began as one
kind. of rock and later were changed
into another kind. All of them began
once as igneous or sedimentary rocks.
The new rocks do not look the same,
for in becoming metamorphic rocks
their structure and often their color
change.

24

Sedimentary rocks are formed deep
under the seas. After they have been
formed, they may become very hot.
Heat helps to change sedimentary rocks.

The weight of the rocks and water on
top of the sedimentary rocks is very
great. The heavy weight or pressure
also helps to change the sedimentary
rocks . Heat and pressure to gether
change the sedimentary rocks into meta­
morphic rocks.

When limestone is changed, it turns
into marble. If shale is changed, it turns
into slate. Both marble and slate are
metamorphic rocks.

Page 27

THE HEAT AND HEAVY WEIGHT, OR PRESSURE, ON SEDIMENTARY

AND IGNEOUS ROCKS HELP TO CHANGE THEM INTO METAMOR­

PHIC ROCKS. AS A VOLCANO PUSHES ITS WAY UP THROUGH

THE EARTH, GREAT HEAT IS CREATED. AS THE VOLCANO PASSES

THROUGH A SEDIMENTARY LAYER, THE HEAT CHANGES THE

SEDIMENTARY ROCK INTO METAMORPHIC ROCK.

Where do

metamorphic

rocks come from?
SEDIMEN­TARY roc ks
are made deep un-
der the seas and

oc ean bo ttoms. So metimes a sea goes
dry. The land moves up and the sedi­
mentary rocks are exposed.

In time the wind and rain wear down
the to p layers o f roc k. Then ano ther
kind of rock is expo sed. The ro ck ex­
posed is metamo rphic ro ck.

To find metamo rphic ro ck, yo u must
visit a place where the land has been
wearing down fo r many years. There
are piaces in the eastern U nited States
and a few in the West where o ne c an see
this kind o f roc k. There are also many
metamorphic roc ks far no rth in Canada.

So metimes metamo rphic roc ks can
be found where old vo lc anoes o nc e
sto e>d. The red ho t lava fro m them o ften
changed o ther roc ks into metamo rphic
rocks.

This typ e o f metamo rphic roc k co uld
occ ur where the vo lc ano pushed its way
up thro ugh the earth, passin g thro ugh
a sediment layer o n the way. Here the
heat helped to c hange the sedimen tary
roc k into metamo rphic roc k.

Page 51

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Page 52

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P rodu ced a n d a p p roved by n oted aut h o r i t i e s , t hese
b o o ks a n swe r the q u est i o n s m ost often asked about

' sc i e n c e , n at u re a n d h i st o ry. T h ey are p resented in a
c l ear , readab l e sty l e , a n d conta i n m a n y c o l o rf u l a n d
i nst ruct ive i l l ustrat i o n s . Read e rs w i l l want to ex p l o re
eac h of t h ese fasc i n at i n g s u bj ects a n d c o l l ect t h ese
vo l u mes as a n a u t h e n t i c , ready-refe re n c e , b as i c l i b ra ry.

500 1 D I N O S A U R S 5032 D O G S
5002 WEAT H E R 5033 P R E H I STO R I C M A M MALS
5004 R O C K S & M I N E RALS 5034 S C I E N C E E X P E R I M ENTS
5007 I N S ECTS 5042 THE A M E R I CA N R E V O L UT I O N
5008 R E PT I LES 5046 MAG N ETS A N D M A G N ET I S M
5009 B I R D S 5053 T R E E S
501 1 B EG I N N I N G S C I E N C E 5055 N O RT H A M E R I CA N I N D IA N S
501 3 T H E H U MA N B O D Y 5064 STA RS
501 4 SEA S H E LLS 5065 A I R P LA N E S A N D THE STO RY
501 6 T H E M I C RO S C O P E O F F L I G HT
5021 C H E M I STRY 5066 F I S H
5022 H O RSES 5069 T RA I N S A N D S H I PS
5024 P R I M I T I VE M A N 5070 ECO LOGY
5031 WI LD FLOWE RS AND OTH E R T I T L E S

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