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Volcanoes and Plate Tectonics Reading Preview 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. as