Download Volcanoes and Plate Tectonics

Volcanoes and
Plate Tectonics
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Key Concepts
• Where lire rnos'l of Ellrth'J
voIatIoes found?
1. Look.t the map of Earth's Aeti~ ~r'lOft in Figu.e 2. What
• How do hot spot "Ok.rooes form 1
KeyTenns
'.olQno •
~fN1
• ~1I<l
• lUng of Fire • ~nd arc
• hot spot
~ Target Reading Skill
Aski"9 QuHtl_ kfo<e \IOU
•ud, prevlew the red headings.. In
I 9'fIPhlc Of~ni"f like m.. ~
below...... ~ wfw~ Of _
quorstion for n<h hNding. AI
\'OU .Nd. ¥«ite tt>e - . . . 10
...............
Where Are Volcanoes Found on Earth's Surface?
----""
symboh are lIS@dtorepresentvokar'lOft7Whatothersymbols
are shown on the map?
2. Do the Ioutions of the volcanoes form a pattern? Do the
lIOkaf"lOe'S ~ relatl!d to any other fealures on Earth's
surface?
Think About It
Ow.eloplng Hypotheses ~Iop a hypothesis to explain where
Earth's \IOk.noes are located.
In 2002, MOUDI Ema erupted in glowing fountains and rivers of
molten rock. localed on Ihe island of SKily in the Mediterra­
nail Sea, Mounl Etna is Europe's largest 'iUkaoo. Ovn" the lasl
2,500 years, it has erupted often. The andent Grttks bdic'Vcd
that Mount EllUl "''as one ~ofHeph.ac:stus,the Gredt god of
fiR. Beneath IN! vokano w.u the forge where Hcphaestus made
beautiful metal objects for the other Gn!dc gods.
The n-uption of a volcaoo is among the I'l'IOOt 3.we--inspiring
n~nu on Eanh. A wl(iiiQ is a weak spor in lhe cruS! where
molten material, or magma, comes to the surfu:e. MajJiii is a
molten mixture of rock~fomlin8 substances, ~ and waler
from the mantle. When magma reaches the sur&cc, it is aJltd
After lava has cooltd, it fornu solid rock.. Lava released
during volcanic activity builds up Eanh's surface.
...... ,
Liln Flow on Mount E_
A lava flow from Mount E_ in Sicily
lImon butied this small building.
Volcanoes and Plate Boundaries
~ are
about 600 ~ vok::mocs OD bOO. Many ~ lit
bmalh the Ja, WMfto it isdifficult for Kinltisls to obsnw and
ITI.Ip than. F'tgute 2 ibows 1M location of 5()IIIt of ~·s
ITUljoc YOk3noec NoIke how voIanoa txUl!" in bdts thai
cxtmd iICfOU rontinmu and ocean5 ODe: majo£ volcanic bdt
is I~ au.aofF~ lOimtd by tbr mmy mIca_th.ll rim the
Pacific Ocean.
Volcanic bdu (orm IIonJ; UN: bowtdarics of Earth's
plates. Al pbte' boun<brics. huge pieces of the crust <fuugc
(pull .pm) or ~ (push ~). N a result, the oust
ofttn fracturn. aIIowinc ~ to roch the surface. Mosl: YOI­
canoes form aIoOI diYUging phil! boundaries 5Uth as mid­
ocean ridJes and aIont ronYn'gins pblc boundaries where
subduction taka pba. For oampk. Mount Elm formed Dear
lht boundary of lbc EuruWJ and Afria,n pbta
Diverging Boundarl.. Vokanocs (onn along the mid­
ocean ridga, which rmrk diverging plale boundaries. RcclIl
thai ridgts are long. un<krwater mountain ranges thai some­
times h.a~ a rift Vitlky down their emltr. Along the rift valley,
lava poUI'$ out of cracks in t~ OCUD Ooor, gradually building
new mountains. Volcanocs also form along div.erging platr
bound,ui" on land. For example, there arc scveullargc vola.·
non along 1M Grtal Rift Valley in East Arriea.
.... ,
u.." of (.-ttl., ~ _
louted MIng tM ~ of
fn
1lKt...- pIMa. The klng of
II
a bett of ~ \tIM drdtf, thI
PKitit 0.:-. 0' I I . . . M1Yr
oaaI_,
.eyoOb ~. ~""""­
nline
Go
c
-­ for;
'
MIn 011"-""­
WtbC":~10]1
~t..-]
f.&l
Converging Bou.ndaries Many volcanoes form near con­
~rging plate boundaries where oceanic pl'lId return to Ihe
mantle. Volcanoes may form ",ilere [WO O«1lnic plates collide
or where an oceanic pblt oollides with a continental plate.
Figure 3 shows how converging plates product volcanoa..
Many volcanoes occur near bounduies where two oceanic
plaid collide. Through subdudion, the older, denser plate
sinb beneath a deep-ocean lR:nch into the mantle. Some of
the rock above the subducting plate melts and forms magma.
Because the magma is Ins d('nse lhan the surrounding rod, it
rises toward tbe surfa<:c. Eventually, the magma brnks through
the OCC'an floor, Cff3ting \'Olcanoes.
..... ,
ValYfIOf!'i at Canv~rg;ng
!lou nd il ries
Vok.lnoes ofteo form ~
two lXNnM: p1ate-s ,oIlk1e
Of
whefe an OU!~ic pIiIle (ollides
with • contintntal plale. In both
The resulting voIanoes ereale a string of islands aUt<! an
island arc. 1be curve of an island an; echoes the cu~ of its
deep-ocean lTen<h. Major island arcs includf' Japan, New
Zealand. Indonesia, the Phi1ippin~ the Aleutians, and the
Caribbean islands.
Volcanod also lXcur where an oaank plate is subducted
beneath a continental plate. Collisions of this type produced
the ~oIClinon of the Andcs Mountains in South America and
the yoicanoes of the Pacific Northwcsi in the United States.
.m..tionl, an oceanic: plate sinks
How did the vokJInoti in the Andft
benNth • lrenth. Rode aboYe
the plate melts to form magma,
..nidl tI>ef1 e<\IPU to the wrf~
MaunuiM form?
M I,v••
",te mo......",
... ,
Hot Spot in a Box
1. Fill a plartil: box half full of
cold wat~. This r@~nts
tMma"*.
1. Mix.fId food coloring with
hot wat~ in a small,
na.row·~fId bott\@to
......
magma.
l. Hold your finger 0Yt'I" till!
r~~nt
Hot Spot Volcanoes
Eo;enlu.lty, the Pacific plate's rnovemeot will talTY
the ~and of Hawaii away from the hot spot.
infefTing Whkh;u,rtd on the rrYp formt!!d fina
Hot Spot Volcanoes
Some volcanoes mull from ~hot spots" in Earlh's mantle. A
hoi spot is an arn when' matc:riaJ from deep within the manlle
rises and then melts, forming magma. A volcano forms above
a hOi spot when magma erupts through the crust and reaches
the surface. Some hOI spot volcanoes lie in the middle of plates
rar from any pialI' boundarid. Other hot SpolS OO::UT on or
near platc boundaries.
A hOI spot in the ocean noar can gradually fonn a series of
volcanic mountains. For example, the H..waiian Islands
formed one by one over millions of yeal'$ as the Pacific plate
drifted over a hOI spot. Hot spots can also form under the con­
tinenr.s. Yellowstone: National Park in Wyoming marks a hot
spot under the North American plate.
Section
mouth of tM bottl@asyou
plac@th@ bonk- in the
C@f1m of ~ box. TIM!
mouth of the bott\@ must
be IJnd~ wat@r.
4. Float a ftat plK@ofplastic:
foam on the wat@raboW'
till! bottJ@ to mod@! a
tKtonic plat@.
S. Tak@yourfingerofftlll!
bottl@ and OOwrw what
hap~r1'5 to the -magma.·
tMking Modeh MeM! till!
plaltic foam slowly along.
Wher@d<M!li the magma
touch the "plu@-1 How
d<M!li this model a hot spot
volcano1
1 Assessment
4@Target Reading Skill Asking Qu@stions \Vork with a
p,artncr to ch«k th.. InsWffS in your graphic organittr.
Reviewing Key Con<epts
1••• Defining Whal is a volcano?
b. Reviewing 'tVh,c,r.- ar.- most vokanocs Iocat<'d!
c.. Reolatlng CauM .nd Effect Whal caUiieIi YOk:anoa; to
form II a dMrging plat.. boundaryf
2. I. Defining Whal is a hot $pOl!
b. Summarizing How doc:s I hoi spot volcano form!
c.. Predicting What f....lura form IS an o«lInic plate
moves 1KT05$, hot spol!
• . . . . . " - Asltrael
..... you _ plaI'''lg' P«ific
Otewo u.- thai will wlsil: \iOkallOe
in the Ring of Fire _ ....' •.1. wnw
I trael ~ deoiibillg the
l)PeS of 'IOkanoes the ~ wlI_
_
i i - "lg IIIlIhy the ...... lOe
fol n-.cl ~ they cId.
Chaptef" l
F.
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