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Actual Test ISection 1[12-17]

N: Listen to part of a lecture on Geology.

e!ale "rofessor:#!!$ so class$ let%s continue loo&ing at 'olcanoes to(ay. Alt)oug) t)etec)ni*ues an( tec)nology use( to o+ser'e 'olcanoes )a'e (e'elope( *uite alot o'er ti!e$ er... it%s still really (ifficult to,accurately pre(ict 'olcanic eruptions.ou &no$ certain specific con(itions are necessary for scientists to !a&e apre(iction,an( e'en t)en$ t)ey can only !a&e, e(ucate( guesses t)at aneruption ill )appen$ +ut ,not)ing specific a+out )en. /0$ let%s ta&e ount St.#elens$ t)at fa!ous 'olcano in as)ington State. It catastrop)ically erupte( inay 1345$ !ay+e so!e of you e'en re!e!+er it$ +ut not +efore plunging

researc)ers$ t)e go'ern!ent$ an( local citi6ens into confusion for !any ee&sa+out )en it oul( erupt. Sure it ga'e off arning signs... +ut t)ey occurre( soerratically so +ot) researc)ers an( ci'ilians (i(n%t t)in& t)ey nee(e( to ta&es)elter. inally$ ount St. #elens erupte( on ay 14t) an( too& e'eryone -inclu(ing eperts - +y surprise +ecause t)e perio( +efore t)e eruption asrelati'ely cal!.

So +ase( on t)is case$ it see!s 'irtually i!possi+le to pre(ict a 'olcanic eruptionit) any (egree of confi(ence$ (oesn%t it8 It (oesn%t )a'e to +e t)at ay...

Actually$ t)ere are factors$ if scientists are o+ser'ant$ t)at can )elp t)e! pre(ict'olcanic +e)a'ior as precisely as possi+le. All rig)t$ so t)e first in(icator is

eart)*ua&e acti'ity.

/0$ as you &no$ 'olcanoes erupt )en !ag!a$ or !olten roc&$ !o'es upar(fro! (eep insi(e t)e eart) an( escapes t)roug) t)e eart)%s surface. No$ t)ereare (ifferent &in(s of eruptions...

Stu(ent9: ;cuse !e$ professor, +ut are !ag!a an( la'a t)e sa!e t)ing8

"rofessor: T)at%s a goo( *uestion,actually$ !ag!a is for!e( )en tre!en(ous)eat insi(e t)e eart) !elts roc&,so !ag!a%s +asically li*uefie( roc& !ie( it)potentially eplosi'e gases. No$ it +eco!es la'a )en it reac)es t)e ;art)%ssurface,

/&$ )ere as I8 /) yea), as !ag!a !o'es upar( toar(s t)e ;art)%ssurface$ it pus)es asi(e soli( roc&. T)is is felt on t)e surface as seis!ic acti'ity -t)at%s rig)t$ eart)*ua&es. No$ scientists use 'ery precise (e'ices$ calle(seis!ograp)s$ to (etect e'en slig)t eart)*ua&es near a 'olcano. So if you%retrying to pre(ict t)e net +ig +loup$ loo& for an increase in seis!ic e'ents$

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especially in t)e nu!+er of lengt)y eart)*ua&es, +ase( on t)at$ scientists cantell if an eruption is on t)e ay...

All rig)t no$ t)e secon( in(icator is gas, see$ gases stay (issol'e( in !ag!a)en it%s still insi(e t)e ;art)$ +ut as t)e !ag!a !o'es upar( t)e gases are

release( an( enter t)e air, so scientists ta&e notice )en certain gas le'els int)e air su((enly

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2. Accor(ing to t)e professor$ )y ere t)e scientists unsure a+out ount St.#elen%s arning signs8

>. In t)e lecture$ t)e professor (escri+es in(icators use( in pre(icting 'olcaniceruptions. In(icate )et)er eac) of t)e folloing is an in(icator.

. Accor(ing to t)e lecture$ )at )appens )en !ag!a eits out t)e si(e of a'olcano8

B. )y (oes t)e professor !ention ount "inatu+o8

C. Listen again to a part of t)e lecture. T)en anser t)e *uestion.

"rofessor: e'en un(er i(eal con(itions$ t)e +est scientists can only co!e up it)a pro+a+ility for an eruption$ not an eact ti!e or (ate@ T)at%s t)e t)ing a+out'olcanoes, an( )y e still can%t li'e net to t)e!.

D. )at (oes t)e professor !ean )en s)e says t)is:ET)atFs t)e t)ing a+out 'olcanoes,

catastrop)icallyplungeeruptgi'e offarning signerraticallys&eptical

ta&e s)elterprece(erelati'e'irtuallypreciselyo+ser'antin(icatortre!en(ousli*uefyeplosi'eseis!icfractureseis!ograp)+loup(issol'esellre((is)crac&lateral

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