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Unit1BasicGeology
Lesson1Geology
Earthscience(alsoknownasgeoscience,thegeosciencesortheEarthsciences),isan
all-embracingtermforthesciencesrelatedtotheplanetEarth.Itisarguablyaspecialcasein
planetaryscience,theEarthbeingtheonlyknownlife-bearingplanet.Therearebothreductionist
andholisticapproachestoEarthsciences.TheformaldisciplineofEarthSciencesmayincludethe
studyoftheatmosphere,oceansandbiosphere,aswellasthesolidearth.Geologyisgenerally
categorizedwithinthegeosciences.
Geology(fromtheGreek,geo,"earth"and,logos,“speech")isanaturalscience,which
studiesthegeologyscienceoftheearth'shistory,composition,andstructure,andtheassociated
processes.Itdrawsuponchemistry,biology,physics,astronomy,andmathematics(notably
statistics)forsupportofitsformulations.
Geologyisaverycomplexscience.TherearemanybranchesofGeology,whichcanbe
groupedunderthemajorheadingsofphysicalandhistoricalgeology.
PhysicalGeology
Physicalgeologyincludesmineralogy,thestudyofthechemicalcompositionandstructureof
minerals;petrology,thestudyofthecompositionandoriginofrock;geomorphology,thestudyof
theoriginoflandformsandtheirsmodificationbydynamicprocesses;geochemistry,thestudyof
thechemicalcompositionoftheearthmaterialsandthechemicalchangesthatoccurwithinthe
earthandonitssurface;geophysics,thestudyofthebehaviorofrockmaterialsandinresponseto
stressesandaccordingtotheprinciplesofphysics;sedimentology,thescienceoftheerosionand
depositionofrockparticlesbywind,water,orice;structuralgeology,thestudyoftheforcesthat
deformtheearth'srocksandthedescriptionandmappingofdeformedrockbodies;economic
geology,thestudyoftheexplorationandrecoveryofnaturalresources,suchasoresand
petroleum;andengineeringgeology,thestudyoftheinteractionoftheearth'scrustwith
human-madestructuressuchastunnel,mines,dams,bridges,andbuildingfoundations.
Historicalgeology
Historicalgeologydealswiththehistoricaldevelopmentoftheearthfromthestudyofits
rocks.Theyareanalyzedtodeterminetheirstructure,composition,andinterrelationshipsandare
examinedforremainsofpastlife.Historicalgeologyincludespaleontology,thesystematicstudy
ofpastlifeforms;stratigraphy,oflayeredrocksandtheirinterrelationships;paleogeography,of
thelocationsofancientlandmassesandtheirboundaries;andgeologicmapping,the
superimposingofgeologicinformationuponexistingtopographicmaps.
Historicalgeologistsdividealltimesincetheinformationoftheearliestknownrocks(c,4
billionyearsago)intofourmajordivisions:thePrecambrian,Paleozoic,Mesozoic,andCenozoic
eras.Each,excepttheCenozoic,endedwithprofoundchangesinthedispositionoftheearth's
continentsandmountainsandwascharacterizedbytheemergenceofnewformsoflife.Broad
cyclicalpatterns,whichrunthroughallhistoricalgeology,includeaperiodofmountainand
continentbuildingfollowedoneoferosionand,inturn,byanewperiodofelevation.
EarlyGeologicStudies
Observationsonearthstructureandprocessesweremadebyanumberoftheancients,
includingHerodotus,Aristotle,Lucretius,Strabo,andSeneca.Theirindividualeffortsinthe
naturalhistoryoftheearth,however,providednosustainedprogress.Theirmajorcontributionis
thattheyattributedthephenomenatheyobservedtonaturalandnotsupernaturalcauses.Manyof
theideasexpressedbythesemenwerenottoresurfaceuntiltheRenaissance.LaterLeonardoda
Vincicorrectlyspeculatedonthenatureoffossilsasremainofancientorganismsandontherole
thatriversplayintheerosionofland.Agricolamadeasystematicstudyoforedepositsinthe
early16thcentury.RobertHookeandNicolausStenobothmadepenetratingobservationsonthe
natureoffossilsandsediments.
EvolutionofModernGeology
Moderngeologybeganinthe18thcentury,whenfieldstudiesbytheFrenchmineralogist
J.E.Gultardandothersprovedmorefruitfulthanspeculation.TheGermangeologistAbraham
GottlobWerner,inspiteofthemanyerrorsofhisspecificdoctrinesandthediversionofmuchof
hisenergyintoafruitlesscontroversy(inwhichhemaintainedthatoriginofallrockswas
aqueous),performedagreatserviceforthesciencebydemonstratingthechronologicalsuccession
ofrocks.
In1795theScottishgeologistJamesHuttonlaidthetheoreticalfoundationformuchofthe
modernsciencewithhisdoctrineofuniformitarianism,firstpopularizedbytheBritishJohn
Playfair.LargelythroughtheworkofsirCharlesLyell,thisdoctrinereplacedtheopposingoneof
catastrophism.Geologyinthe19thcenturywasinfluencedalsobytheworkofCharlesDarxvin
andenrichedbytheresearchesoftheSwiss-AmericanLouisAgassiz.
Inthe20thcentury,geologyhasadvancedatanever-increasingpace.Theunravelingofthe
mysteryofatomicstructureandthediscoveryofradioactivityallowedprofoundadvancesinmany
phasesofgeologicresearch.ImportantdiscoveriesweremadeduringtheInternationalGeological
Year(1957-58),whenscientistsfrom67nationsjoinedforceininvestigatingproblemsinall
branchesofgeology.Thesystematicsurveyoftheearth'soceansbroughtradicalchangesin
conceptsofcrustalevolution.
Asaresultofnumerousflybyspacecraft,geologicalstudieshavebeenextendedtoinclude
remotesensingofotherplanetsandsatellitesinthesolarsystemandthemoon.Laboratory
analysesofrockssamplesbroughtbackfromthemoonhaveprovidedinsightintotheearlyhistory
ofnear-earthspace.On-siteanalysesofMartiansoilsamplesandphotographicmappingofits
surfacehavegivencluesaboutitscompositionandgeologichistory,includingthepossibilitythat
Marsoncehadenoughwatertoformoceans.Photographsofthemanyactivevolcanoeson
Jupiter'smoonIohaveprovidedcluesaboutearth'searlyvolcanicactivity.Geologicalstudiesalso
havebeenfurtheredbyorbitinglaboratories,suchasthesixlaunchedbetween1964inthe
OrbitingGeophysicalObservatory(OGO)seriesandthePolarOrbitingGeomagneticSurvey
(POGS)satellitelaunchedin1990;remote-imagingspacecraft,suchastheU.S.Landsatprogram
(Landsat7,launchedin1999,wasthemostrecent)andFrenchSPOTseries(SPOT4,launchedin
1988,wasthemostrecentintheprogram);andgeologicalstudiesonspaceshuttlemissions.
NewWordsandPhrases
1.mineralogy/產(chǎn)明_一n.礦物學
2.petrology/y。一n.巖石學
3.geomorphologyZn.地貌學
4.geochemistryZn.地球化學
5.geophysics/G_、n.地球物理學
6.sedimentology/_0O耳_?二,.缸O/G\n,沉積學
7.structuralgeology構造地質學
8.economicgeology經(jīng)濟地質學(礦床學)
9.paleontologyZytR2「.缸o/。'n.古生物學
10.stratigraphyn.地層學
11.paleogeographyZYTGJJO/Gn.古地理學
12.Precambrian/2?,.阡n.adj.前寒紀
13.Paleozoic/Y?.?g_i_\n.adj.古生代(界)
14.MesozoicZTOu_I_O\n.adj.中生代(界)(的)
15.CenozoicZ3'n.adj.新生代(界)(的)
16.catastrophism一?.?一匚>。?災難論
17.remotesensingn.遙感
18.spaceshuttle航天飛機
19.Herodotus一一\(希臘歷史學家)希羅多德(約公元前485-約公元前425)
20.Werne維爾納(1750/817)德國地質學家、礦物學家,水成論的創(chuàng)立者
21.uniformitarianismZ。一?匯_?n.均變論
22.Aristotle/?.?一。_、4\亞里士多德(公元前322-公元前384古希臘大哲學家,科學家)
23.Renaissancen.文藝復興(時期)
24.CharlesDarwin/??―一\查爾斯達爾文,英國博物學家,進化論創(chuàng)立者
25.Landsat/n.(美國)地球資源(探測)衛(wèi)星
26.aqueous[??-;]adj.含水的,似水的
Translations&InterpretationsofdifficultSentences
1Broadcyclicalpatterns,whichrunthroughallhistoricalgeology,includeaperiodof
mountainandcontinentbuildingfollowedoneoferosionand,inturn,byanewperiodof
elevation.
貫穿著整個地史時期最主要的循環(huán)模式,包括一段時期的造山和大陸,隨后發(fā)生的侵蝕
作用,然后,是一個新時期的抬升。
2Theirindividualeffortsinthenaturalhistoryoftheearth,however,providednosustained
progress.
然而,他們的個人努力并沒有使得地球的自然歷史研究持續(xù)進步。
3LaterLeonardodaVincicorrectlyspeculatedonthenatureoffossilsasremainofancient
organismsandontherolethatriversplayintheerosionofland.
后來,列奧納多?達?芬奇把化石的本質作為古代生物的殘體進行了正確的考辨反思,
并推測了河流對陸地的剝蝕作用。
Lesson2TheEarth
Ingeologyandastronomy,theEarthisthefifthlargestplanetofthesolarsystemandtheonly
planetdefinitelyknowntosupportlife.Gravitationforceshavemoldedtheearth,likeallcelestial
bodies,intoasphericalshape.However,theearthisnotanexactsphere,beingslightlyflattenedat
thepolesandbulgingattheequator,whichmeansthattheequatorialdiameterof12,756kmis
largerthanthepolardiameterof12,714km.Andthemassoftheearthis6X1024kg.Thealtitude
ofthesurfacefeaturesrangefrom11kmbelowto9kmabovesealevel,and70%ofthesurfaceis
coveredwithliquidwater,whichmakesituniqueinthesolarsystem.Additional,Earthhasan
atmospherereachingseveralhundredkmintospace,consistingof78%nitrogen,21%oxygen,1%
othergasesincludingcarbondioxideandwatervapour.Earthistheonlyplanetinoursolarsystem
tohavelargequantitiesoffreeoxygeninitsatmosphere.
Knowledgeoftheearth'sinteriorhasbeen
gatheredbythreemethods:bytheanalysisof
earthquakewavespassingthroughtheearth,by
analogywiththecompositionofmeteorites,andby
considerationoftheearth'ssize,shape,anddensity.
Researchbythesemethodsindicatesthatthe
FigureofTheEarth'sLayersearthhasazonedinterior,consistingofconcentric
shellsdifferingfromoneanotherbysize,chemicalmakeup,anddensity.TheplanetEarthismade
upofthreemainshells:theverythin,brittlecrust,themantle,andthecore;themantleandcore
areeachdividedintotwoparts.Althoughthecoreandmantleareaboutequalinthickness,the
coreactuallyformsonly15percentoftheEarth'svolume,whereasthemantleoccupies84percent.
Thecrustmakesuptheremaining1percent.
TheEarth'sCrustandtheMoho
Becausethecrustisaccessibletous,itsgeologyhasbeenextensivelystudied,andtherefore
muchmoreinformationisknownaboutitsstructureandcompositionthanaboutthestructureand
compositionofthemantleandcore.Withinthecrust,intricatepatternsarecreatedwhenrocksare
redistributedanddepositedinlayersthroughthegeologicprocessesoferuptionandintrusionof
lava,erosion,andconsolidationofrockparticles,andsolidificationandrecrystallizationofporous
rock.Bythelarge-scaleprocessofplatetectonics,abouttwelveplates,whichcontain
combinationsofcontinentsandoceanbasins,havemovedaroundontheEarth'ssurfacethrough
muchofgeologictime.Theedgesoftheplatesaremarkedbyconcentrationsofearthquakesand
volcanoes.CollisionsofplatescanproducemountainsliketheHimalayas,thetallestrangeinthe
world.Theplatesincludethecrustandpartoftheuppermantle,andtheymoveoverahot,
yieldinguppermantlezoneatveryslowratesofafewcentimetersperyear,slowerthantherateat
whichfingernailsgrow.Thecrustismuchthinnerundertheoceansthanundercontinents.
TheboundarybetweenthecrustandmantleiscalledtheMohorovicicdiscontinuity(or
Moho);itisnamedinhonorofthemanwhodiscoveredit,theCroatianscientistAndrija
Mohorovicic.Noonehaseverseenthisboundary,butitcanbedetectedbyasharpincrease
downwardinthespeedofearthquakewavesthere.TheexplanationfortheincreaseattheMohois
presumedtobeachangeinrocktypes.DrillholestopenetratetheMohohavebeenproposed,and
aSovietholeontheKolaPeninsulahasbeendrilledtoadepthof12kilometers,butdrilling
expenseincreasesenormouslywithdepth,andMohopenetrationisnotlikelyverysoon.
TheEarth'sMantle
Extendingtoadepthofc.2,900km,themantleprobablyconsistsofverydense(average
c.3.9)rockrichinironandmagnesiumminerals.Althoughtemperaturesincreasewithdepth,the
meltingpointoftherockisnotreachedbecausethemeltingtemperatureisraisedbythegreat
confiningpressure.Atdepthsbetweenc.100andc.200kminthemantle,aplasticzone,called
theasthenosphere,isfoundtooccur.Presumablytherocksinthisregionareveryclosetomelting,
andthezonerepresentsafundamentalboundarybetweenthemovingcrustalplatesoftheearth's
surfaceandtheinteriorregions.Themoltenmagmathatintrudesupwardintocrustalrocksor
issuesfromavolcanointhefromoflavamayoweitsorigintoradioactiveheatingortotherelief
ofpressureinthelowercrustanduppermantlecausedbyearthquakefaultingoftheoverlying
crustalrocks.Similarly,itisthoughtthattheheatenergyreleasedintheupperpartofmantle
hasbrokentheearth'scrustintovastplatesthatslidearoundontheplasticzone,settingup
stressesalongtheplatemarginsthatresultintheformationoffoldsandfaults.
TheEarth'sCore
Thoughtobecomposedofironandnickel,thedense(c.l1.0)coreoftheearthliesbelow
mantle.Theabruptdisappearanceofdirectcotnpressionalearthquakewaves,whichcannottravel
thoughliquids,atdepthsbelowc.2,900kmindicatesthattheouter2,200kmofthecorearemolten.
Itisthought,however,thattheinner1,260kmofthecorearesolid.Theoutercoreisthoughttobe
thesourceoftheearth'smagneticfield:Inthe'dynamotheory'advancedbyW.M.ElasserandE.
Bullard,tidalenergyorheatisconvertedtomechanicalenergyintheformofcurrentsintheliquid
core;thismechanicalenergyisthenconvertedtoelectromagneticenergy,whichweseeasthe
magneticfield.
TheEarth'sAge
theearthisestimatedtobe4.5billionto5billionyearsold,basedonradioactivedatingof
lunarrocksandmeteorites,whicharethoughttohaveformedatthesametime.Theoriginofthe
earthcontinuestobecontroversial.Amongthetheoriesastoitsorigin,themostprominentare
gravitationalcondensationhypotheses,whichsuggestthattheentiresolarsystemwasformedat
onetimeinasingleseriesofprocessesresultingintheaccumulationofdiffuseinterstellargases
anddustintoasolarsystemofdiscretebodies.Oldandnowgenerallydiscreditedtheories
invokedextraordinaryevents,suchasgravitationaldisruptionofastarpassingclosetothesunor
theexplosionofacompanionstartothesun.
NewWordsandPhrases
1.geology[O/Gn.地質學
2.astronomy一?.?一4、n.天文學
3.solarsystemn.太陽系
4.gravitation-。叼-?、n.地心吸力
5.celestialbody10一4」\n.天體
6.equatorn.赤道
7.altitude/n.(海拔)高度
8.meteoriteZP?-LU、n.隕石
9.concentricZadj.同心的
10.brittle/,上£、adj.易碎的
11.intricateZadj.復雜的
12.collisionZi_夕/」.、n.碰撞
13.Himalayas20GL\n.喜馬拉雅山脈
14.Moho/「力」、n.莫霍面
Mohoroviidiscontinuity莫霍不連續(xù)面
15.asthenosphere。?―>。\n.軟流圈
16.radioactiveZ?:…白、adj.放射性的
17.magma/n.巖漿
18.compressionalZi_+adj.壓縮的,縱(波)的
19.dynamotheory[n.(地磁場成因的)發(fā)電機理論
20.lunar[adj.月亮的,月球的
21.gravitationalcondensationhypotheses(天體形成的)重力凝聚假設,也稱吸積作用
22.crustalplate地殼板塊
23.interstellarZ一。心\adj.星際的
24.lava/償~一」'n.熔巖
Translations&InterpretationsofdifficultSentences
1Researchbythesemethodsindicatesthattheearthhasazonedinterior,consistingof
concentricshellsdifferingfromoneanotherbysize,chemicalmakeup,anddensity.
通過這些方法研究表明地球的內部是由同心圈層組成,這些圈層的大小,化學組成以及
密度互不相同。
2Althoughthecoreandmantleareaboutequalinthickness,thecoreactuallyformsonly15
percentoftheEarth'svolume,whereasthemantleoccupies84percent.
雖然地核和地幔在重量上是近似均等的,地核只占地球體積的大約15%,而地幔占了
84%o
3Withinthecrust,intricatepatternsarecreatedwhenrocksareredistributedanddepositedin
layersthroughthegeologicprocessesoferuptionandintrusionoflava,erosion,andconsolidation
ofrockparticles,andsolidificationandrecrystallizationofporousrock.
當如巖漿噴發(fā)和侵入,侵蝕,巖石顆粒的固結以及多孔巖石的凝固和重結晶等地質過程
作用于地殼時,創(chuàng)造了地殼內復雜的格局。
4Althoughtemperaturesincreasewithdepth,themeltingpointoftherockisnotreached
becausethemeltingtemperatureisraisedbythegreatconfiningpressure.
雖然隨著深度的增加溫度升高,但由于熔點隨著壓力的增加而升高,溫度并未達到巖石
的熔點。
5Themoltenmagmathatintrudesupwardintocrustalrocksorissuesfromavolcanointhe
fromoflavamayoweitsorigintoradioactiveheatingortotherelieffpressureinthelowercrust
anduppermantlecausedbyearthquakefaultingoftheoverlyingcrustalrocks.
上覆地殼巖石的地震斷層會導致下地殼和上地幔的熱輻射或解壓,這可能是是熔融的巖
漿侵入地表巖石或火山噴發(fā)熔巖的主要原因。
6Theoutercoreisthoughttobethesourceoftheearth9smagneticfield:Inthe4dynamo
theory,advancedbyW.M.ElasserandE.Bullard,tidalenergyorheatisconvertedtomechanical
energyintheformofcurrentsintheliquidcore;thismechanicalenergyisthenconvertedto
electromagneticenergy,whichweseeasthemagneticfield.
外地核被認為是地球磁場的來源,根據(jù)W.M.ElasserandE.Bullard的“地磁場理論”,潮
汐能或者熱可以轉化為液芯中的機械能流,機械能再轉化為電磁能,也就是我們所知道的磁
場。
Lesson3EarthquakeandVolcanoes
Earthquake
Earthquakeistremblingorshakingmovementoftheearth'ssurface.Mostearthquakesare
minortremors.Largerearthquakesusuallybeginwithslighttremorsbutrapidlytaketheformof
oneormoreviolentshocks,andendinvibrationsofgraduallydiminishingforcecalled
aftershocks.Thesubterraneanpointoforiginofanearthquakeiscalleditsfocus;thepointonthe
surfacedirectlyabovethefocusistheepicenter.Themagnitudeandintensityofanearthquakeis
determinedbytheuseofscales,e.g.,theRichterscaleandMercalliscale.
Mostearthquakesarecausallyrelatedtocompressionalortensionalstressesbuiltupatthe
marginsofthehugemovinglithosphericplatesthatmakeuptheearth'surface.Theimmediate
causeofmostshallowearthquakesisthesuddenreleaseofstressalongafault,orfractureinthe
earth'scrusfresultinginmovementoftheopposingblocksofrockpastoneanother.These
movementscausevibrationstopassthroughandaroundtheearthinwavefrom,justasripplesare
generatedwhenapebbleisdroppedintowater.Volcaniceruption,rockfalls,landslides,and
explosionscanalsocauseaquake,butmostoftheseareofonlylocalextent.
ThereareseveraltypesofearthquakewavesincludingP,orprimary,waves,whichare
compressionalandtravelfastest;andS,orsecondary,waves,whicharetransverse,i.e.,theycause
theearthtovibrateperpendicularlytothedirectionoftheirmotion.Surfacewavesconsistof
severalmajortypesandarecalledL,orlong,waves.SincethevelocitiesofthePandSwavesare
affectedbythechangesinthedensityandrigidityofthematerialthroughwhichtheypass,the
boundariesbetweentheregionsoftheearthknownasthecrust,mantle,andcorehavebeen
discernedbyseismologists,scientistswhodealwiththeanalysisandinterpretationofearthquake
waves.SeismographsareusedtorecordP,SandL'waves.ThedisappearanceofSwavesbelow
depthsof2,900kmindicatesthatatleasttheouterpartoftheearth'scoreisliquid.
Theeffectsofanearthquakearestrongestinabroadzonesurroundingtheepicenter.The
extentofearthquakevibrationandsubsequentdamagetoaregionispartlydependenton
characteristicsoftheground.Forexample,earthquakevibrationslastlongerandareofgreater
waveamplitudesinunconsolidatedsurfacematerial,suchaspoorlycompactedfillorriver
deposits;bedrockareasreceivefewereffects.Theworstdamageoccursindenselypopulated
urbanareaswherestructuresarenotbuilttowithstandintenseshaking.There,Lwavescan
producedestructivevibrationsinbuildingsandbreakwaterandgaslines,startinguncontrollable
fires.
Damageandlossoflifesustainedduringanearthquakeresultfromfallingstructuresand
flyingglassandobjects.Flexiblestructuresbuiltonbedrockaregenerallymoreresistantto
earthquakedamagethanrigidstructuresbuiltonloosesoil.Incertainareas,anearthquakecan
triggermudslides,whichslipdownmountainslopesandcanburyhabitationsbelow.Asubmarine
earthquakecancausetsunamis,damagingwavesthatrippleoutwardfromtheearthquake
epicenterandinundatecoastalcities.
Onaverageabout1,000earthquakeswithintensitiesof5.0orgreaterarerecordedeachyear.
Greatearthquakes(intensity8.()orhigher)occuronceayear,majorearthquakes(intensity7.0-7.9)
occur18timesayear,strongearthquakes(intensity6.0-6.9)10timesamonth,andmoderate
earthquakes(intensity5.0-5.9)morethantwiceaday.Becausemostoftheseoccurunderthe
oceanorinunderpopulatedareas,theypassunnoticedbyallbutseismologists.
Volcanoes
Volcanoesareventsorfissuresintheearth'scrustthoughwhichgases,moltenrock,orlava,
andsolidfragmentsaredischarged.Thetermvolcanoiscommonlyappliedbothtotheventandto
theconicalmountainbuiltuparoundtheventbytheeruptedrockmaterials.Volcanoesare
describedasactive,dormant,orextinct.Thesoilresultingfromdecompositionofvolcanic
materialsisextremelyfertile,andtheashitselfisagoodpolishingandcleansingagent.
Volcanoesarefoundinassociationwithmidoceanridgesystemsandalongconvergentplate
boundaries,suchasaroundthePacificOcean's'RingofFire',theringofplateboundaries
associatedwithvolcanicislandarcsandoceantrenchessurroundingthePacificOcean.Isolated
volcanoesalsoforminthemidoceanareaofthePacificapparentlyunrelatedtocrustalplate
boundaries.Theseseamountsandvolcanicislandchains,suchastheHawaiianchain,mayform
fromrisingmagmaregionscalledhotspots.
Morethan500volcanoesknowntohaveeruptedontheearth'ssurfacesincehistorictimes,
andmanymorehaveeruptedontheoceanfloorunobservedbyhumans.Fiftyvolcanoeshave
eruptedintheUnitedStates,whichranksthird,behindIndonesiaandJapan,inthenumberof
historicallyactivevolcanoes.Oftheworld'sactivevolcanoes,morethanhalfarefoundaroundthe
perimeterofthePacific,aboutathirdonmidoceanicislandsandinanarcalongthesouthofthe
Indonesianisland,andaboutatenthintheMediterraneanarea,Africa,andAsiaMinor.
Evidenceofextraterrestrialvolcanicactivityalsohasbeenfound.Spaceprobeshavedetected
theremnantsofancienteruptionsonearth'smoon,Mars,andMercury;theseprobablyoriginated
billionsofyearsago,sincethesebodiesarenolongercapableofvolcanicactivity.Triton(a
satelliteofNeptune),Io(asatelliteofJupiter),andVenusaretheonlybodiesinthesolarsystem
besidesearththatareknowntobevolcanicallyactive.Thevolcanicprocessesthatoccurinthe
outerportionofthesolarsystemareverydifferentfromthoseintheinnerpart.Eruptionsonearth,
Venus,Mercury,andMarsareofrockymaterialandaredrivenbyinternalheat.lo'seruptionsare
probablysulfurcompoundsdrivenbytidalinteractionswithJupiter.Triton'seruptionsareofvery
volatilecompounds,suchasmethaneornitrogen,drivenbyseasonalheatingfromthesun.
Terrestrialvolcaniceruptionsmaytakeoneormoreoffourchiefforms,orphases,knownas
Hawaiian,Strombolian,Vulcanian,andPelean.IntheHawaiianphasethereisarelativelyquiet
effusionofbasalticlavaunaccompaniedbyexplosionsortheejectionoffragments;theeruptions
ofMaunaLoaontheislandofHawaiiaretypical.TheStrombolianphasederivesitsnamefrom
thevolcanoStromboliintheLipari,orAeolian,Islands,NofSicily.Itappliestocontinuousbut
milddischargesinwhichviscouslavaisemittedinrecurringexplosion;theejectionof
incandescentmaterialproduceluminousclouds.Amoreexplosivevolcaniceruptionisthe
Vulcanian,wherethemagma(lavabeforeemission)accumulatesintheupperleveloftheventbut
isblockedbyahardenedplugoflavathatformsbetweenconsecutiveexplosions.Whenthe
explosivegaseshavereachedacriticalpressurewithinthevolcano,massesofsolidandliquid
rockeruptintotheairandcloudsofvaporformoverthecrater.ThePelean,derivedformMont
Pelee,isthemostviolent,emittingfineash;hot,gas-chargedfragmentsoflava;andsuperheated
steaminanincandescent'cloud'thattravelsdownhillatgreatspeed.Eruptionsareoften
accompaniedbytorrentialrainscausedbythecondensationofsteam.Theeruptedfragmentsvary
insize,includingminuteparticlesofvolcanicdustandash,lapilli(cinderorpellets),bombs
(roundedorellipsoidalmassesofhardenedmagma),andhugemassescalledblocks.
NewWordsandPhrases
1.aftershock?.Xn.余震
2.subterranean_。。?門—專、adj.地下的
3.RichterscaleZn.里氏震級
4.Mercalliscale/干o金?麥加利震級
5.compressionalstress壓應力
6.tensionalstress張應力
7.focus/n.焦點,焦距,(地震的)震源
8.epicenter/n.震中
9.rigidityn.剛度
10.seismologist/孑"6_0/,\n.地震學家
11.seismographZJ-?°+i_O-=^>\n.地震儀
12.waveamplitudeZ,.阡y/JU?0、n.波幅
13.bedrocki/$OO\n.巖基
14.mudslide/工1Gn.泥石流
15.tsunami?金?n.海嘯
16.inundate?/:0cV.淹沒
17.volcanon.火山
18.dormantZO"?:?一\adj.休眠的
19.convergentplateboundary會聚板塊邊緣
20.oceantrench海溝
21.perimeter_阡%_\n.周長,周邊
22.extralerreslrialV一adj.地球外的,宇宙的
24.
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