九年级英语Natural environment.docx
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九年级英语Natural environment.docx
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九年级英语Naturalenvironment
Naturalenvironment
MuchattentionhasbeengiventopreservingthenaturalcharacteristicsofHopetounFalls,Australia,whileallowingampleaccessforvisitors.
BachalpseeintheSwissAlps;generallymountainousareasarelessaffectedbyhumanactivity.
Thenaturalenvironment,commonlyreferredtosimplyastheenvironment,isatermthatencompassesalllivingandnon-livingthingsoccurringnaturallyonEarthorsomeregionthereof.
Theconceptofthenaturalenvironmentcanbedistinguishedbycomponents:
∙Completeecologicalunitsthatfunctionasnaturalsystemswithoutmassivehumanintervention,includingallvegetation,animals,microorganisms,soil,rocks,atmosphereandnaturalphenomenathatoccurwithintheirboundaries.
∙Universalnaturalresourcesandphysicalphenomenathatlackclear-cutboundaries,suchasair,water,andclimate,aswellasenergy,radiation,electriccharge,andmagnetism,notoriginatingfromhumanactivity.
Thenaturalenvironmentiscontrastedwiththebuiltenvironment,whichcomprisestheareasandcomponentsthatarestronglyinfluencedbyhumans.Ageographicalareaisregardedasanaturalenvironment(withanindefinitearticle),ifthehumanimpactonitiskeptunderacertainlimitedlevel(similartosection1above.
Composition
Mainarticle:
Earthscience
Earthscience(alsoknownasgeoscience,thegeosciencesortheEarthSciences),isanall-embracingtermforthesciencesrelatedtotheplanetEarth[1].Therearefourmajordisciplinesinearthsciences,namelygeography,geology,geophysicsandgeodesy.Thesemajordisciplinesusephysics,chemistry,biology,chronologyandmathematicstobuildaqualitativeandquantitativeunderstandingoftheprincipalareasorspheresoftheEarthsystem.Earthsciencegenerallyrecognizes4spheres,thelithosphere,thehydrosphere,theatmosphere,andthebiosphere[2];thesecorrespondtorocks,water,air,andlife.Somepractitionersinclude,aspartofthespheresoftheEarth,thecryosphere(correspondingtoice)asadistinctportionofthehydrosphere,aswellasthepedosphere(correspondingtosoil)asanactiveandintermixedsphere.
Geologicalactivity
Avolcanicfissureandlavachannel.
Mainarticle:
Geology
TheEarth'scrust,orContinentalcrust,istheoutermostsolidlandsurfaceoftheplanet,ischemicallyandmechanicallydifferentfromunderlyingmantles,andhasbeengeneratedlargelybyigneousprocessesinwhichmagma(moltenrock)coolsandsolidifiestoformsolidland.Platetectonics,mountainranges,volcanoes,andearthquakesaregeologicalphenomenathatcanbeexplainedintermsofenergytransformationsintheEarth'scrust[3],andmightbethoughtofastheprocessbywhichtheearthresurfacesitself.BeneaththeEarth'scrustliesthemantlewhichisheatedbytheradioactivedecayofheavyelements.Themantleisnotquitesolidandconsistsofmagmawhichisinastateofsemi-perpetualconvection.Thisconvectionprocesscausesthelithosphericplatestomove,albeitslowly.Theresultingprocessisknownasplatetectonics.[4][5][6][7]Volcanoesresultprimarilyfromthemeltingofsubductedcrustmaterial.CrustmaterialthatisforcedintotheAsthenospheremelts,andsomeportionofthemeltedmaterialbecomeslightenoughtorisetothesurface,givingbirthtovolcanoes!
[5]
Oceanicactivity
Mainarticle:
Ocean
PolarbearsontheseaiceoftheArcticOcean,neartheNorthPole.
TheshoreofthePacificOceaninSanFrancisco,California.
Earth'soceans
(WorldOcean)
∙ArcticOcean
∙AtlanticOcean
∙IndianOcean
∙PacificOcean
∙SouthernOcean
Anoceanisamajorbodyofsalinewater,andaprincipalcomponentofthehydrosphere.Approximately71%oftheEarth'ssurface(anareaofsome361millionsquarekilometers)iscoveredbyocean,acontinuousbodyofwaterthatiscustomarilydividedintoseveralprincipaloceansandsmallerseas.Morethanhalfofthisareaisover3,000meters(9,800ft)deep.Averageoceanicsalinityisaround35partsperthousand(ppt)(3.5%),andnearlyallseawaterhasasalinityintherangeof30to38ppt.Thoughgenerallyrecognizedasseveral'separate'oceans,thesewaterscompriseoneglobal,interconnectedbodyofsaltwateroftenreferredtoastheWorldOceanorglobalocean.[8][9]Thisconceptofaglobaloceanasacontinuousbodyofwaterwithrelativelyfreeinterchangeamongitspartsisoffundamentalimportancetooceanography.[10]
Themajoroceanicdivisionsaredefinedinpartbythecontinents,variousarchipelagos,andothercriteria:
thesedivisionsare(indescendingorderofsize)thePacificOcean,theAtlanticOcean,theIndianOcean,theSouthernOcean(whichissometimessubsumedasthesouthernportionsofthePacific,Atlantic,andIndianOceans),andtheArcticOcean(whichissometimesconsideredaseaoftheAtlantic).ThePacificandAtlanticmaybefurthersubdividedbytheequatorintonortherlyandsoutherlyportions.Smallerregionsoftheoceansarecalledseas,gulfs,baysandothernames.Therearealsosaltlakes,whicharesmallerbodiesoflandlockedsaltwaterthatarenotinterconnectedwiththeWorldOcean.TwonotableexamplesofsaltlakesaretheAralSeaandtheGreatSaltLake.
Atmosphere,climateandweather
Mainarticles:
Earth'satmosphere,climate,andweather
Atmosphericgasesscatterbluelightmorethanotherwavelengths,creatingabluehalowhenseenfromspace.
TheatmosphereoftheEarthservesasakeyfactorinsustainingtheplanetaryecosystem.ThethinlayerofgasesthatenvelopstheEarthisheldinplacebytheplanet'sgravity.Dryairconsistsof78%nitrogen,21%oxygen,1%argonandotherinertgases,carbondioxide,etc.;butairalsocontainsavariableamountofwatervapor.Theatmosphericpressuredeclinessteadilywithaltitude,andhasascaleheightofabout8kilometresattheEarth'ssurface:
theheightatwhichtheatmosphericpressurehasdeclinedbyafactorofe(amathematicalconstantequalto2.71...).[11][12]TheozonelayeroftheEarth'satmosphereplaysanimportantroleindepletingtheamountofultraviolet(UV)radiationthatreachesthesurface.AsDNAisreadilydamagedbyUVlight,thisservestoprotectlifeatthesurface.Theatmospherealsoretainsheatduringthenight,therebyreducingthedailytemperatureextremes.
Effectofglobalwarming
Mainarticle:
Globalwarming
TheretreatofAletschGlacierintheSwissAlps(situationin1979,1991and2002),duetoglobalwarming.
Thepotentialdangersofglobalwarmingarebeingincreasinglystudiedbyawideglobalconsortiumofscientists,whoareincreasinglyconcernedaboutthepotentiallong-termeffectsofglobalwarmingonournaturalenvironmentandontheplanet.Ofparticularconcernishowclimatechangeandglobalwarmingcausedbyanthropogenic,orhuman-madereleasesofgreenhousegases,mostnotablycarbondioxide,canactinteractively,andhaveadverseeffectsupontheplanet,it'snaturalenvironmentandhumans'existence.Effortshavebeenincreasinglyfocusedonthemitigationofgreenhousegasesthatarecausingclimaticchanges,ondevelopingadaptativestrategiestoglobalwarming,toassisthumans,animalandplantspecies,ecosystems,regionsandnationsinadjustingtotheeffectsofglobalwarming.Someexamplesofrecentcollaborationtoaddressclimatechangeandglobalwarminginclude:
AnotherviewoftheAletschGlacierintheSwissAlps,whichduetoglobalwarming,hasbeendecreasing.
∙TheUnitedNationsFrameworkConventionTreatyandconventiononClimateChange,tostabilizegreenhousegasconcentrationsintheatmosphereatalevelthatwouldpreventdangerousanthropogenicinterferencewiththeclimatesystem.[13]
∙TheKyotoProtocol,whichistheprotocoltotheinternationalFrameworkConventiononClimateChangetreaty,againwiththeobjectiveofreducinggreenhousegasesinanefforttopreventanthropogenicclimatechange.[14]
∙TheWesternClimateInitiative,toidentify,evaluate,andimplementcollectiveandcooperativewaystoreducegreenhousegasesintheregion,focusingonamarket-basedcap-and-tradesystem.[15]
Asignificantlyprofoundchallengeistoidentifythenaturalenvironmentaldynamicsincontrasttoenvironmentalchangesnotwithinnaturalvariances.Acommonsolutionistoadaptastaticviewneglectingnaturalvariancestoexist.Methodologically,thisviewcouldbedefendedwhenlookingatprocesseswhichchangeslowlyandshorttimeseries,whiletheproblemarriveswhenfastprocessesturnsessentialintheobjectofthestudy.
Life
Femalemallardandducklings-reproductionisessentialforcontinuinglife
Mainarticles:
LifeandBiosphere
Althoughthereisnouniversalagreementonthedefinitionoflife,scientistsgenerallyacceptthatthebiologicalmanifestationoflifeischaracterizedbyorganization,metabolism,growth,adaptation,responsetostimuliandreproduction.[16]Lifemayalsobesaidtobesimplythecharacteristicstateoforganisms.
Propertiescommontoterrestrialorganisms(plants,animals,fungi,protists,archaeaandbacteria)arethattheyarecellular,carbon-and-water-basedwithcomplexorganization,havingametabolism,acapacitytogrow,respondtostimuli,andreproduce.Anentitywiththesepropertiesisgenerallyconsideredlife.However,noteverydefinitionoflifeconsidersallofthesepropertiestobeessential.Human-madeanalogsoflifemayalsobeconsideredtobelife.
ThebiosphereisthepartofEarth'soutershell—includingair,land,surfacerocksandwater—withinwhichlifeoccurs,andwhichbioticprocessesinturnalterortransform.Fromthebroadestgeophysiologicalpointofview,thebiosphereistheglobalecologicalsystemintegratingalllivingbei
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