工程地質(zhì)英語

PAGEPAGE64EngineeringGeology（TheFirstEdition）Writer:LuZhaohui&ChenDongliangEnglishCorrector:LiXiaoyanShaanxiDepartmentofCivilEngineeringandArchitecture

EngineeringGeologyContentsIntroduction……………………….…………1ChapterOneRock…………..31.1GeologicalAction…………………31.2InnerStructureofEarth……….…..31.3TheMainMineralsintheRock…………………..41.4TheRock………….6ChapterTwoGeologicalStructure………...142.1GeologicalTimeandChronologicalScale…….….142.2BasicShapeandClassificationofGeologicalStructure……….…192.3TheImportanceoftheStudyofGeologicalStructure……………28ChapterThreeUndergroundWater……………………..…313.1ThePhysicalPropertiesandChemicalCompositionofGroundwater………..…..313.2TheClassificationofGroundwater……………….323.3MovingLawofGroundwater………………...…..363.4TheInfluenceofGroundwateronEngineering……….…….……36ChapterFourTheMainEngineeringGeologyProblemsinCivilEngineering394.1TheErosionofRiver…………...…394.2Landslide………….394.3Collapse………………………...…454.4KarstandEarthCave………4.5TheEngineeringProblemsinUndergroundEngineering…..…….47ChapterFiveTheEngineeringGeologyinvestigation……………...…….505.1Introduction………………….……505.2EngineeringGeologicalsurvey………………….525.3EngineeringGeologicSearch…………………….555.4TheIn-situSoilTest………………575.5TheReportofEngineeringGeologyinvestigation…………..…..58IntroductionIntroductionEngineeringGeology(工程地質(zhì))triestousegeologyforidentifyingpotentialproblemsarisingfromgroundconditions;Itdescribeshowtoinvestigatethoseconditionsandtodefineanengineeringresponsethatwilleitheravoidorreduceoreveneliminatetheproblemsrevealed.Thecourseisdesignedforstudentsofgeology,engineeringgeologyandcivilengineeringandillustrateshowgeologyisrelatedtocalculationsofstability,deformationandgroundwaterflow.DefinitionEngineeringGeologyconcernsabouttheinfluenceofgeologyonconstructionanddealswithapplicationofthegeosciences(地球科學)toassurethesafety,efficiency,andeconomyofengineeringactivities.Itisdevotedtotheinvestigation,researchandsolutionoftheengineeringandenvironmentalproblemsthatmayariseastheresultoftheinteractionbetweengeologyandengineeringactivitiesaswellastothepredictionandthedevelopmentofmeasuresforpreventionorremediationofgeologicalhazards.EngineeringGeologyalsoconcernswiththegeologicalproblemsencounteredincivilengineering.Itsmaintaskistoinvestigateandevaluatethegeologicalengineeringproblems,providethebasicinformationfortheplan,designandconstructionofthecivilengineering.CourseObjectivesTheprimarypurposeofthiscourseistogivestudentsinCivilandGeologicalEngineeringanunderstandingofearthmaterialsandtheirproperties,andthenaturalprocessesthatactonthosematerialsandaffectmanmadestructures.ThisknowledgewillbeappliedtovariousexamplesfromCivilEngineeringtoGeologicalEngineering.Asecondarycoursegoalisbasedupontheassumptionthatmostofyouinthisclasswilldealprofessionallywithgeologistsinyourcareers.Thusanunderstandingofthetermsandmethodsusedbygeologistswillbetterenableyoutobettercommunicatewithgeoscientistsandtoproperlyinterpretproblemsencounteredinyourfields.Demands(requirements)1.TomasterthebasicconceptsaboutEngineeringGeology.2.Tocomprehendthemaingeologicalproblemsoccurredinengineering.3.Toknowhowtheproblemshappened,howwecanpreventit.4.Classroomdiscipline.5.Exams:Exams,otherthan“make-ups”willconsistofavarietyofobjectivetypequestions–translation,choice,true/false,fill-insorblanks,andwillincludeafewshortquestions.WordsandPhrase:EngineeringGeology工程地質(zhì)geosciences地球科學remediationn.補救,糾正geologicalhazard地質(zhì)災害naturalprocess自然界發(fā)展進程

ChapterOneRock1.1GeologicalAction1.1.1Whatisgeologicalaction？[DefinitionofGeologicalAction]Itmeanstheactionsthatmakealterationforthecomposition,structure,shapeoftherockcyclebecauseofthenaturaldynamics.1.1.2TheclassificationoftheGeologicalAction(1)Outer-dynamicsgeologicalactionDynamicsourceisfromthesun,gravity,attractionforcebetweenthesunandthemoon.A:Weathering→therockisdestroyedattheplacewhereitwasformedbecauseoftheouterdynamics.B:Erosion→rockbodyisseparatedfromitsmotherrockbecauseofthewater,wind,glacier(冰河).C:Carrying→theprocessthatrockiscarriedfromoneplacetoantherplace.D:Sedimentation→theprocessinwhichthecarryingmaterialssinktothebottomofgroundwhenthepowerofgravityofthematerialsisbiggerthanthecarryingforce.E:Rock-formationaction→theprocessthatthematerialssinktogroundsurfacetobecomehardorsolidrockbody.(2)Inner-dynamicsgeologicalaction(Thedynamicssourceisfromtheearth)A:CrustmovementB:Magmatism(Magmaticactivities)(巖漿作用)Magmaticintrusionandvolcaniceruption.C:EarthquakeD:Metamorphism(變質(zhì)作用)Becauseofthehighpressureand/ortemperature,therockischangedtoanewkindofrock.Thisrockiscalledmetamorphicrock.Everygeologicalphenomenaistheresultofgeologicalaction.Itincludes:mineral,rock,landshape(mountain,river,plain),tectonics.1.2InnerStructureofEarthTheearthincludestwoparts:outsidelayerandsolidearth.Theoutsidelayeriscomposedoftheatmosphere,waterenclosingandthebiosphere.Similarly,solidearthismadeupoftheearth'scrust,earthmantleandearth'score.Thedensityoftheearth'scrustis2.7~2.9g/cm3,madeupofvariousrocksseenintheearth'ssurface.Theearthmantleisin2900kmdepthundertheearth’scrust.Thedensityoftheearthmantleis3.32~4.64g/cm3,madeupofsilicatematerialrichinFe,Mg.Thepartundertheearthmantleiscalledtheearth'score.Thedensityoftheearth'scoreis11~16g/cm3,madeupofmaterialincludingFe,Ni.Theearth'scoreismadeupofthesolidnuclearinsideandtheliquidstateoutside.Fig1.1CircularlayersoftheearthTheknowledgeabouttheinsidelayersofearthmainlycomesfromthestudyonelasticwaveofearthquake.Accordingtoresearch,thereisaseismicwavewithlowertempoattheearthmantletop;5%materialsareinmeltstatethere.Itwascalledflowlayer.Thelayerinsolidstateabovetheflowlayeriscalledthelithosphere.Thelithosphere,havingstrongerrigidity,splitintoalotofpieces,iscalledtheplate.Theplatesmoveontheflowlayer.Thisisaplatemovement.Thatistheoriginofthetectonicmovement(構(gòu)造運動)too.1.3TheMainMineralsintheRockSincemineralsarethebuildingblocksofrocks,itisimportantthatyoulearntoidentifythemostcommonvarieties.Mineralscanbedistinguishedbyusingvariousphysicaland/orchemicalcharacteristics,but,sincechemistrycannotbedeterminedreadilyinthefield,thephysicalpropertiesofmineralsareusedtoidentifythem.Physicalpropertiesofmineralsincludefeaturessuchascrystalform(結(jié)晶體),hardness(relativetoasteelbladeoryourfingernail),color,luster,andstreak(thecolorwhenamineralisgroundtopowder).1.Quartz(SiO2)石英Quartzisaglassy-looking,transparentortranslucentmineralwhichvariesincolorfromwhiteandgreytosmoky.Whenthereareindividualcrystalstheyaregenerallyclear,whileinlargermassesquartzlooksmoremilkywhite.Quartzishard,itcaneasilyscratchasteelknifeblade.Inmanyrocks,quartzgrainsareirregularinshapebecausecrystalfacesarerareandquartzdoesnothaveacleavage(ie,itdoesnotbreakonregularflatfaces).2.Calcite(CaCO3),carbonaterock方解石，硅酸鹽Shape:rhomb(菱形)Hardness:3Actingwithacid:givingoffcarbondioxide.3.Dolomite(白云石，MgCO3)ThesameascalciteActingwithpowderofdolomitewillgiveoffcarbondioxide4.Feldspar（silicaterock）長石Orthoclase：正長石Plagioclase：斜長石Feldsparisanothercommon,light-coloredrock-formingmineral.Insteadofbeingglassylikequartz,itisgenerallydulltoopaquewithaporcelain-likeappearance.Colorvariesfromred,pink,andwhite.Feldsparisalsohardbutcanbescratchedbyquartz.Feldsparinigneousrocksformswell-developedcrystalswhichareroughlyrectangularinshape,andtheycleaveorbreakalongflatfaces.Thegrains,incontrasttoquartz,oftenhavestraightedgesandflatrectangularfaces,someofwhichmeetatrightangles.5.Amphibole(閃石)Themostcommonamphiboleishornblende(角閃石).Hornblendeisquitesimilartoaugite(斜輝石)inthatbotharedarkminerals,howeverhornblendecrystalsaregenerallylonger,thinnerandshinierthanaugiteandthemineralcross-sectionsarediamond-shaped.6.Pyroxene輝石Themostcommonpyroxenemineralisaugite.Augiteisgenerallydarkgreentoblackincolorandformsshort,stubbycrystalswhich,ifyoulookatanend-onsection,havesquareorrectangularcross-sections.7.Mica云母Micaiseasilydistinguishedbyitscharacteristicofpeelingintomanythin,flatsmoothsheetsorflakes.Thisissimilartothecleavageinfeldsparexceptthatinthecaseofmicathecleavageplanesareinonlyonedirectionandnorightanglefacejoinsoccur.Micamaybewhiteandpearly(muscovite)ordarkandshiny(biotite).8.Talc滑石Talcoccursingranularorfoliatedmassessometimesknownassoapstone(皂石).Itiswhitetogreen,sometimesgreyorbrownish.Itisverysoftandwillbescratchedbyafingernail.Itfeelsgreasy.9.Gypsum(plasterstone,石膏)10.Kaolinite(高嶺石)11.Montmorillonite蒙脫石12.Watermica水云母Luster:soillusterAbsorbingwater1.4TheRock1.4.1TheclassificationofrockaccordingtothecauseofformationIgneousrock:巖漿巖Abyssalrock(深成巖)Shallowrock(淺成巖)Eruptiverock(噴出巖)Sedimentaryrock:沉積巖Clasticrock碎屑巖Clayrock粘土巖Chemicalrock化學巖Biochemicalrock生物化學巖Metamorphicrock:變質(zhì)巖1.4.2.Igneousroc1）TheformationofigneousrockDeepwithintheEarth,rockiskeptinamoltenstateduetoextremetemperatureandpressure.

Thismoltenrockiscalledmagma(巖漿).

Themagmaisconstantlymovingandsometimesmovesitswaytothesurfacethroughthecracksinthesolidrock.

Onceitreachesthesurface,itiscalledlava(溶巖).

Thelocationitpushesthroughtothesurfaceiscalledavolcano.

Theopeninginthevolcanothatthelavaeruptsoutofiscalledavent(火山口).Formanyvolcanos,thereismorethanonevent.

Oftenvolcanoshaveafunnelshapewithapitatthetop.

Thispitiscalledavolcaniccrater.

Ifthiscraterbecomesverylarge,thewallsofthecratermightcollapsetoproduceafeaturecalledacaldera(噴火山口).2）TheclassificationofigneousrockAccordingtothetectonicoftheigneousrock按產(chǎn)狀：IntrusiveIgneousRocks-usuallymediumtocoarsegrainedtextureduetoslowcooling,typicallylightcolored.ExtrusiveIgneousRocks-glassyorfine-grainedduetorapidcooling,mayhavevoidsduetodegassingofthemagma,typicallydarkcolored.SilicaContentandMineralComposition按二氧化硅和礦物含量AcidIgneousRocks-silicarich(>65%byweight),composedmainlyoffelsic(長英礦物)orlightcoloredminerals(eg.feldspars,quartz)IntermediateIgneousRocks-silicamedium(50-65%byweight),composedmainlyofplagioclasefeldspars(斜長石),somemaficminerals,withsomequartz.BasicIgneousRocks-silicapoor(<50%byweight),containsignificantamountsofmafic(鐵鎂質(zhì)的)ordarkcoloredferromagnesianminerals(含鎂礦物)(eg.olivines,pyroxenes,amphiboles,micas).Nofreequartz.3）ThedescriptionofmainigneousrockGranite(abyssalrock)花崗巖Graniteisanigneousrockthatiscomposedoffourminerals.Thesemineralsarequartz,feldspar,mica,andusuallyhornblende.Graniteformsasmagmacoolsfarundertheearth'ssurface.Becauseithardensdeepunderground,itcoolsveryslowly.Thisallowscrystalsofthefourmineralstogrowlargeenoughtobeeasilyseenbythenakedeye.Graniteisanexcellentmaterialforbuildingbridgesandbuildingsbecauseitcanwithstandthousandsofpoundsofpressure.Itisalsousedformonumentsbecauseitweathersslowly.Engravingsinthegranitecanbereadforhundredsofyears,makingtherockmorevaluable.GraniteisquarriedinmanyplacesintheworldincludingtheUnitedStates.TheStateofNewHampshirehasthenickname"GranitePorphyriticgranite(shallowrock)花崗斑巖moderatecrystallization(quartz-feldspar-blackmica).Rhyolite(eruptiverock)流紋巖Rhyoliteisverycloselyrelatedtogranite.Thedifferenceisrhyolitehasmuchfinercrystals.Thesecrystalsaresosmallthattheycannotbeseenbythenakedeye.Rhyoliteisanextrusiveigneousrockhavingcooledmuchmorerapidlythangranite,givingitaglassyappearance.Themineralsthatmakeuprhyolitearequartz,feldspar,mica,andhornblende.Diorite閃長巖abyssalrock,wellcrystallization,(feldspar,quartz,amphibole)Dioriteporphyrite閃長斑巖shallowrock,mediancrystallizationfeldspar,quartzamphibolcAndesite閃長巖eruptiverock,nocrystallizationPyroxenire輝巖abyssalrock,wellcrystallization,amphibole,phyroxenefeldsparBasalt玄武巖Basaltsaredarkcolored,fine-grainedextrusiverock.Themineralgrainsaresofinethattheyareimpossibletodistinguishwiththenakedeyeorevenamagnifyingglass.Theyarethemostwidespreadofalltheigneousrocks.Mostbasaltsarevolcanicinoriginandwereformedbytherapidcoolingandhardeningofthelavaflows.Somebasaltsareintrusive,havingcooledinsidetheEarth'sinterior.[eruptiverock,nocrystallization]Ultrabasicrock超基性巖(SiO2<45%)Olivinerock橄欖石abyssalrockwellcrystallization,olivinepyroxene(橄欖輝石).1.4.3Sedimentaryrock1）TheformationofsedimentaryrockForthousands,evenmillionsofyears,littlepiecesofourearthhavebeeneroded,brokendownandwornawaybywindandwater.Theselittlebitsofoureartharewasheddownstreamwheretheysettletothebottomoftherivers,lakes,andoceans.Layerafterlayeroferodedearthisdepositedontopofeach.Theselayersarepresseddownmoreandmorethroughtime,untilthebottomlayersslowlyturnintorock.2）TheclassificationofsedimentaryrockSedimentsaresubdividedintothreetypes:Clasticordetritalsedimentscomprisingparticlesofvarioussizescarriedinsuspensionbywind,waterorice.Sandisanexampleofaclasticsediment.Siltandsandsizeparticlesarecarriedinsuspensionbywind,waterandice.Chemicalorprecipitatedsedimentswhicharecarriedinaqueoussolution.Salt(halite)isanexampleofachemicalprecipitate.Organicorbiogenicsediments,precipitatedoraccumulatedbybiologicalagents.Manyorganismspromotetheprecipitationofcalcitetoformbiogenicallyprecipitatedcalcareousmuds.A.Clasticrock碎屑巖Clasticsedimentaryrocksareformedbytheparticlesorclaststhatarecementedtogethertoformtherock.Thestrengthofcementationisoftenanimportantcharacteristicinengineeringterms.Well-cementedquartzsandstonescanbeverystrongmechanically,whereasweakuncementedsandstonesarerelativelyweakrocks.Siltstones,mudstonesandshalesareusuallyweakrocksbecauseofthedominanceofplatyclaymineralsthatprovidedlittlefrictionalresistance.Conglomeratesandsandstoneshaverelativelyhighvolumesofvoids(pores)andareeconomicallyimportantasaquifersforwatersupplyandreservoirrocksforgasandpetroleum.B.Clayrock粘土巖Thediameteroftheparticleislessthan0.005mm.C.Chemicalrock化學巖Chemicalsedimentaryrocksareclassifiedaccordingtothepredominantmineralsprecipitatedtoformtherockandtheirtexture.Theyaredepositedbyprecipitationfromsolutionratherthanreleasefromsuspension.D.OrganicChemicalrock生物化學巖Organicorbiogenicsedimentaryrocksarerocksthatowetheirexistencetobiologicalprocesses.Theymaybeclasticaccumulationsofanimalskeletonsdebris(manylimestone),biologicallycatalysedprecipitates(someironstones),accumulationsofplantdetritus(coal)oralterationproductsofsiliceousorganisms(chert).3）ThedescriptionofsedimentaryrockGravelstone(conglomerate);(d>2mm)礫巖Conglomeraterocksaresedimentaryrocks.Theyaremadeupoflargesedimentslikesandandpebbles.Thesedimentissolargethatpressurealonecannotholdtherocktogether;itisalsocementedtogetherwithdissolvedminerals.(clasticrock)Sandstone(d=2~0.05mm)砂巖Sandstonerocksaresedimentaryrocksmadefromsmallgrainsoftheminerals,quartzandfeldspar.Theyoftenforminlayersasseeninthispicture.Theyareoftenusedasbuildingstones.Siltstone(d=0.05~0.005mm)Mudstone(d<0.005mm)泥巖,mineral:kaolinite(高嶺石),montorillonite(蒙脫石),watermicaShale頁巖Shalerockisatypeofsedimentaryrockformedfromclaythatiscompactedtogetherbypressure.Theyareusedtomakebricksandothermaterialthatisfiredinakiln.Limestone石灰?guī)rLimestonerocksaresedimentaryrocksthataremadefromthemineralcalcitewhichcamefromthebedsofevaporatedseasandlakesandfromseaanimalshells.Thisrockisusedinconcreteandisanexcellentbuildingstoneforhumidregions.Color:greyMineral:Calcite+HCl→CO2↑Dolomiterock白云巖Color:white-greyMineral:dolomiteGypsum石膏Gypsumrocksaresedimentaryrocksmadeupofsulfatemineralandformedastheresultofevaporatingseawaterinmassiveprehistoricbasins.ItisverysoftandisusedtomakePlasterofParis(熟石膏),casts,molds,andwallboards.1.4.4Metamorphicrocksaregeneratedbyrecrystallization(重結(jié)晶)ofeitherigneousorsedimentaryrocksbytheactionofanyorallofthefollowing:pressure,temperature,poreFluids.1）TheformationandclassificationofMetamorphicrocksThetypeofmetamorphicrockisdeterminedbytheparentrockandthepressureor/andtemperatureconditions.Ingeneral,metamorphismcauses:GrowthofnewmineralsDeformationandrotationofmineralgrainsRecrystallizationofmineralsaslargergrainsProductionofstrongbrittlerocksoranisotropicrocksweakinshear.(1)RegionalMetamorphicRocks原生變質(zhì)巖Generatedmainlybypressureintherootsofmountainbelts.(2)ContactMetamorphicRocks接觸變質(zhì)巖Generatedmainlybytemperatureatthemarginsofigneousintrusions.Sometimescalledthermalmetamorphicrocks.Asecondcommonsubdivisionofmetamorphicrocksisbasedontexture:Thetypeofmetamorphicrockisdeterminedbytheparentrockandthepressureor/andtemperatureconditions.Ingeneral,metamorphism(變質(zhì)作用)causes:(1)Non-foliatedRocks塊狀巖石Recrystallizedtexturebutnopreferredmineralorientation.(2)FoliatedRocks片理狀巖石Withstrongmineralorientationand/ormineralbandingorlayering.2）ThedescriptionofMetamorphicrocksMarble大理石Marbleismetamorphosedlimestoneordolomite.Bothlimestoneanddolomitehavealargeconcentrationofcalciumcarbonate(CaCO3).Marblehasmanydifferentsizesofcrystals.Marblehasmanycolorvariancesduetotheimpuritiespresentatformation.Someofthedifferentcolorsofmarblearewhite,red,black,mottledandbanded,gray,pink,andgreen.Marbleismuchharderthanitsparentrock.Thisallowsittotakeapolishwhichmakesitagoodmaterialforuseasabuildingmaterial,makingsinktops,bathtubs,andacarvingstoneforartists.Today,headstonesaremadefrommarbleandgranitebecausebothoftheserocksweatherveryslowlyandcarvewellwithsharpedges.Quartzite石英巖Quartziteiscomposedofsandstonethathasbeenmetamorphosed.Quartziteismuchharderthantheparentrock,sandstone.Itformsfromsandstonethathascomeintocontactwithdeeplyburiedmagmas.Quartzitelookssimilartoitsparentrock.Thebestwaytotellquartzitefromsandstoneistobreaktherocks.Sandstonewillshatterintomanyindividualgrainsofsandwhilequartzitewillbreakacrossthegrains.WordsandPhrase:Geologicalaction地質(zhì)作用weathering風化作用sedimentation沉積作用Magmatism(Magmaticactivities)巖漿作用Metamorphism變質(zhì)作用Metamorphicadj.變形的,變質(zhì)的,改變結(jié)構(gòu)的atmospheren.大氣,空氣,氣氛biospheren.生物圈silicaten.[化]硅酸鹽seismicwave地震波tempon.(音樂)速度、拍子,發(fā)展速度lithospheren.[地]巖石圈platen.板塊crystalform結(jié)晶體bladen.刀刃,刀片lustern.光彩,光澤streakv.飛跑,加上條紋ground；v.磨(碎),碾(碎),折磨；grind的過去式transparentadj.透明的,顯然的,明晰的translucentadj.半透明的,透明的scratchvt.亂涂,勾抹掉,擦,刮,搔,抓,挖出cleavagen.劈開,分裂acidn.[化]酸；adj.酸的,諷刺的,刻薄的carbondioxide二氧化碳opaqueadj.不透明的porcelain-likeadj.瓷質(zhì)的,有瓷器光澤的rectangularadj.矩形的,成直角的cleavev.劈,劈開,裂開peelv.剝,削,剝落brownishadj.呈褐色的greasyadj.多脂的,油脂的,油污的funneln.漏斗,煙窗IntrusiveIgneousRocks侵入巖ExtrusiveIgneousRocks噴出巖degassvt.除去瓦斯AcidIgneousRocks酸性巖IntermediateIgneousRocks中性巖BasicIgneousRocks基性巖withstandvt.抵擋,經(jīng)受住engravingsn.雕刻術(shù),雕版,雕版圖downstreamadj.下游的settlevi.下陷,沉淀,沉積detritaladj.由巖屑形成的suspensionn.懸浮液precipitatedadj.突如其來的,陡然下降(或下落)的aqueousadj.水成的cementvi.粘牢siltstonesn.[地]粉砂巖shalesn.[地]頁巖,泥板巖platyn.(巖石)裂成平坦薄片的；[地質(zhì)]板狀的,扁平狀的conglomeratesv.聚結(jié)petroleumn.石油skeletonsn.(動物之)骨架,骨骼debrisn.碎片,殘骸organismsn.生物體,有機體chertn.[礦]燧石,黑硅石pebblesn.小圓石,小鵝卵石anisotropicadj.各向異性的subdivisionn.細分

ChapterTwoGeologicalStructure2.1GeologicalTimeandChronologicalScale2.1.1GeologicalTimeGeologicaltimeisamethodoforderingandmeasuringpastevents.Theorderingofeventsusesagroupofobservationalmethodsknownas:absolutedatingmethodsandrelativedatingmethods.1AbsoluteDatingmethodsAbsolutedatingmethodsarethosethatgenerateanageinyears.Therearetwoprincipalmethods:oneisthemethodwhichrelyoneventinthegeologicalrecordwithverystrongannualcyclicity(周期性),suchastreegrowthrings,coralgrowthcyclesvarves(annualclaysedimentlayers).Anothermethodismorecommonlyusednowadayswhichrelyonthedecayofnaturallyoccurringradiogenicisotopes.Radiometricdating(同位素年代測定法)isnotwithoutdifficultiesbutisbyfarthemostwidespreadmethodappliedtodetermineabsoluteagesbetween100and4500Ma.ThesamedecayprocessisresponsibleforthetemperaturegradientwithintheEarth(geothermalgradient).Uranium(鈾),Thorium（釷）andPotassium（鉀）arebyfarthemostcommonradiogenicisotopesintheEarth'scrust.Radiocarbonisimportantindatingorganicremainsfromtherelativelyrecentpast.2RelativedatingmethodsRelativedatingmethodsusegeologicalprinciplestoplaceeventsinchronologicalorder,whichincludestratasuperpositionmethod(地層對比法),fossilsuccessionmethod(古生物化石法),themethodofrocklayerscontactrelation(地層接觸關(guān)系法).(1)Theprincipleofsuperpositionstatesthatolderbedsarecoveredbyyoungerbeds.Inotherword,theyoungestunitisusuallyatthetopinasedimentarysequence.YoungestYoungestlayerOldestlayerFig2.1Theprincipleofsuperpositionstates(2)Theprincipleoffossilsuccessionstatesthatorganismsevolvethroughtime,sothatparticularformscanbeusedasagemarkerswherevertheyarefound.Fig2.2Theprincipleoffossilsuccessionstates(3)Themethodofrocklayerscontactrelationstatesthatthecontactrelationsamongrocklayersisthehistoryrecordsofcrustmovement,magmaactivities.Sogeologicaleventscanbeorderedbytherelationofrocklayers;Theseincludetherelationsamongsedimentaryrock,therelationsamongtheigneousrock,therelationsbetweensedimentaryrockandigneousrock.(a)TherelationsamongsedimentaryrockTherelationsamongsedimentaryrockcanbedividedintoconformity(整合接觸)andunconformity(不整合接觸).Theconformitymeansthatstratawereformedinastablesedimentaryenvironment.Thedipandstrikeofstrataarebasicallythesame.Theunconformitymeanthereisabreakinsedimentation,aperiodoferosionoranepisodeofdeformation.Unconformitiesrangefromminorerosivebreakstostrongangulardiscordancesinbedding.Anunconformityindicatesaperiodwhennorockrecordisaccumulated.Theyaretime-breaksofindeterminatelength.(b)TherelationsamongigneousrockCross-cuttingrelationshipsamongigneousrocks(seediagrambellow)indicatethatintrusionrocksmustbeyoungerthantherockstheycut.(c)Therelationsbetweensedimentaryrockandigneousrock.Cross-cuttingrelationshipsbetweenigneousrocksandsedimentaryrockindicatethatsedimentaryrockincludingpebbles(小圓石，鵝卵石)andfragmentsmustbeolderthanthehostrockcontainingthem.Deformationofanyrocksaffectedbyadeformationevent(foldingortilting)mustpre-datethedeformationepisode.Fig2.3Cross-cuttingrelationshipsamongigneousrocks2.1.2ChronologicalscaleThegeologictimescalewasoriginallyasetofrelativedatesbutthevariouseons(宙),eras(代),periods（紀）andepochs（世）havenowbeenaccuratelydatedwiththeaidofradiometricmethods.Theimportantdatesare:4,600Ma-theageoftheEarthandSolarSystem3,600Ma-theearliestlife570Ma-thefirstappearanceofabundantandvariedorganicforms200Ma-thebreak-upofthesupercontinentPangea([地質(zhì)]泛古陸).66Ma-thedisappearanceofthedinosaurs(恐龍).Thegeologictimescaleisusuallypresentedinadistortedform,87%ofthetotaltimespanisrepresentedbytheProterozoic(元古代)andArcheaneons(太古代)ofthePrecambrian(前寒武紀).Table2.1GeologicalTimeScaleEON(宙)ERA（代）PERIOD（紀）EPOCH（世）MILLIONYEAR（距今百年）顯生宙

Phanerozoic新生代

Cenozoic第四紀QuaternaryHolocene全新世現(xiàn)代Today--0.01Pleistocene更新世0.01--1.8第三紀Tertiary上新世

Pliocene1.8--5.3中新世

Miocene5.3--23漸新世

Oligocene23--36.5始新世

Eocene36.5--53古新世

Palaeocene53--65中生代

Mesozoic白堊紀

Cretaceous65--145侏羅紀

Jurassic145--208三疊紀

Triassic208--248古生代

Palaeozoic二疊紀

Permian248--290石炭紀

Carboniferous290--360泥盆紀

Devonian360--410志留紀

Silurian410--438奧陶紀

Ordovician438--510寒武紀

Cambrian510--570元古宙

Precambrian元古代

Proterozoic震旦紀

Sinian570--800800--2,500太古宙

Archaean太古代

Archaeozoic2,500--4,600Initialstageofearth