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Yourwebbrowser(Safari7)isoutofdate.Formoresecurity,comfortand thebestexperienceonthissite: Updateyourbrowser Ignore A U S T RA L I A A N D O C E A N I A: P H Y S I C A L G E O G RA P H Y Forthecompleteencyclopedicentrywithmediaresources,visit: http://www.nationalgeographic.org/encyclopedia/oceania-physical-geography/ OceaniaisaregionmadeupofthousandsofislandsthroughouttheCentraland SouthPacificOcean.ItincludesAustralia,thesmallestcontinentintermsof totallandarea.MostofAustraliaandOceaniaisunderthePacific,avastbody ofwaterthatislargerthanalltheEarth’scontinentallandmassesandislands combined.Thename“Oceania”justlyestablishesthePacificOceanasthe definingcharacteristicofthecontinent. OceaniaisdominatedbythenationofAustralia.Theothertwomajor landmassesofOceaniaarethemicrocontinentofZealandia,whichincludesthe countryofNewZealand,andthewesternhalfoftheislandofNewGuinea, madeupofthenationofPapuaNewGuinea.Oceaniaalsoincludesthreeisland regions:Melanesia,Micronesia,andPolynesia(includingtheU.S.stateof Hawaii). Oceania’sphysicalgeography,environmentandresources,andhuman geographycanbeconsideredseparately. Oceaniacanbedividedintothreeislandgroups:continentalislands,high islands,andlowislands.Theislandsineachgroupareformedindifferentways andaremadeupofdifferentmaterials.Continentalislandshaveavarietyof physicalfeatures,whilehighandlowislandsarefairlyuniformintheirphysical geography. ContinentalIslands 1of9 Continentalislandswereonceattachedtocontinentsbeforesealevelchanges andtectonicactivityisolatedthem.Tectonicactivityreferstothemovement andcollisionofdifferentsections,orplates,oftheEarth’scrust. Australia,Zealandia,andNewGuineaarecontinentalislands.Thesethree regionssharesomephysicalfeatures.Allthreehavemountainrangesor highlands—theGreatDividingRangeinAustralia;theNorthIslandVolcanic PlateauandSouthernAlpsinNewZealand;andtheNewGuineaHighlandsin PapuaNewGuinea.Thesehighlandsarefoldmountains,createdastectonic platespressedtogetherandpushedlandupward.NewZealandandPapuaNew Guineaalsohavevolcanicfeaturesasaresultoftectonicactivity. Althoughtheysharesomelandscapefeatures,eachoftheseregionshas distinctphysicalfeaturesthatresultedfromdifferentenvironmentalprocesses. Australia’slandscapeisdominatedbytheOutback,aregionofdesertsand semi-aridland.TheOutbackisaresultofthecontinent’slargeinlandplains,its locationalongthedryTropicofCapricorn,anditsproximitytocool,dry, southerlywinds.NewZealand’sglaciersarearesultoftheislands’high elevationsandproximitytocool,moisture-bearingwinds.PapuaNewGuinea’s highlandrainforestsarearesultoftheisland’shighelevations,proximityto tropical,moisture-bearingwinds,andlocationrightbelowthewarmEquator. HighIslands Highislands,alsocalledvolcanicislands,arecreatedasvolcaniceruptionsbuild uplandovertime.Theseeruptionsbeginunderwater,whenhotmagmais cooledandhardenedbytheocean.Overtime,thisactivitycreatesislandswith asteepcentralpeak—hencethename“highisland.”Ridgesandvalleysradiate outwardfromthepeaktowardthecoastline. TheislandregionofMelanesiacontainsmanyhighislandsbecauseitisamajor partofthe“RingofFire,”astringofvolcanoesaroundtheboundaryofthe 2of9 PacificOcean.ThispartoftheRingofFireisontheboundaryofthePacificplate andtheAustralianplate.Thisisaconvergentplateboundary,wherethetwo platesmovetowardeachother.ImportantvolcanicmountainsinMelanesia includeMountTomanivi,Fiji;MountLamington,PapuaNewGuinea;andMount Yasur,Vanuatu. LowIslands Lowislandsarealsocalledcoralislands.Theyaremadeoftheskeletonsand livingbodiesofsmallmarineanimalscalledcorals.Sometimes,coralislands barelyreachabovesealevel—hencethename“lowisland.”Lowislandsoften taketheshapeofanirregularringofverysmallislands,calledanatoll, surroundingalagoon.Anatollformswhenacoralreefbuildsuparounda volcanicisland,thenthevolcanicislanderodesaway,leavingalagoon.Atolls aredefinedasoneislandeventhoughtheyaremadeupofmultiple communitiesofcoral. TheislandregionsofMicronesiaandPolynesiaaredominatedbylowislands. TheKwajaleinAtollintheMarshallIslands,forexample,iscomposedof97 islandsandisletsthatsurroundoneofthelargestlagoonsintheworld,withan areaof2,173squarekilometers(839squaremiles).ThenationofKiribatiis composedof32atollsandonesolitaryislanddispersedover3.5millionsquare kilometers(1.35millionsquaremiles)ofthePacificOcean. IslandFloraandFauna TheevolutionoffloraandfaunaacrosstheislandsofAustraliaandOceaniais unique.ManyplantsandanimalsreachedtheislandsfromsouthernAsiaduring thelastglacialperiod,whensealevelswerelowenoughtoallowfortravel.After sealevelsrose,speciesadaptedtotheenvironmentofeachislandor communityofislands,producingmultiplespeciesthatevolvedfromacommon ancestor.Duetoitsisolationfromtherestoftheworld,AustraliaandOceania hasanincrediblyhighnumberofendemicspecies,orspeciesthatarefound 3of9 nowhereelseonEarth. Plantstraveledbetweenislandsbyridingwindoroceancurrents.Birdscarried theseedsoffruitsandplantsandspreadthembetweenislandswiththeir droppings.Ferns,mosses,andsomefloweringplantsrelyonsporesorseeds thatcanremainairborneforlongdistances.Coconutpalmsandmangroves, commonthroughoutAustraliaandOceania,produceseedsthatcanfloaton saltywaterforweeksatatime.ImportantfloweringplantsnativetoAustralia andOceaniaincludethejacaranda,hibiscus,pohutukawa,andkowhai.Other indigenoustreesincludethebreadfruit,eucalyptus,andbanyan. BirdsareverycommoninAustraliaandOceaniabecausetheyareoneofthe fewanimalsmobileenoughtomovefromislandtoisland.Therearemorethan 110endemicbirdspeciesinAustraliaandOceania,includingmanyseabirds. Manyflightlessbirds,suchasemus,kiwis,cassowaries,wekas,andtakahes,are nativetoAustralia,PapuaNewGuinea,andNewZealand.ThePacificIslands havemorethan25speciesofbirdsofparadise,whichexhibitcolorfulplumage. LizardsandbatsmakeupthemajorityofAustraliaandOceania’snativeland animals.Lizardspeciesincludethegoanna,skink,andbeardeddragon. AustraliaandOceaniahasmorethanahundreddifferentspeciesoffruitbats. ThefewnativelandanimalsinAustraliaandOceaniaareunusual.Australiaand Oceaniaistheonlyplaceintheworldthatishometomonotremes—mammals thatlayeggs.AllmonotremesarenativetoAustraliaandPapuaNewGuinea. Thereareonlyfivelivingspecies:theduckbillplatypusandfourspeciesof echidna. ManyofthemostfamiliaranimalsnativetoAustraliaandOceaniaare marsupials,includingthekoala,kangaroo,andwallaby.Marsupialsare mammalsthatcarrytheirnewbornyounginapouch.Almost70percentofthe marsupialsonEartharenativetoOceania.(Therestarenativetothe Americas.) 4of9 InAustraliaandOceania,marsupialsdidnotfacethreatsorcompetitionfrom largepredatorssuchaslions,tigers,orbears.Theredkangaroo,theworld’s largestmarsupial,cangrowupto2meters(6feet)tall,andweighasmuchas 100kilograms(220pounds).IntheAmericas,marsupialssuchaspossumsare muchsmaller. MarineFloraandFauna Themarineenvironmentisanimportantandinfluentialphysicalregionin AustraliaandOceania.Theregioniscomposedofthreemarinerealms: TemperateAustralasia,CentralIndo-Pacific,andEasternIndo-Pacific.Marine realmsarelargeoceanregionswhereanimalandplantlifearesimilarbecause ofsharedenvironmentalandevolutionaryfactors. TheTemperateAustralasiarealmincludestheseassurroundingthesouthern halfofAustraliaandtheislandsofNewZealand.Thisrealmisoneoftheworld’s richestareasforseabirds.Itscold,nutrient-richwaterssupportadiversityof plantsandfishthatseabirdsfeedon.Theseseabirdsincludedifferentspeciesof albatross,petrel,andshearwater,aswellastheAustralasiangannetand rockhopperpenguin. TheCentralIndo-Pacificrealmincludestheseassurroundingthenorthernhalf ofAustralia,PapuaNewGuinea,SolomonIslands,Vanuatu,NewCaledonia,Fiji, andTonga.Thismarinerealmhasthegreatestdiversityoftropicalcoralinthe worldandincludestheworld’stwolargestcoralformations:Australia’sGreat BarrierReefandtheNewCaledoniaBarrierReef.TheGreatBarrierReef,a UNESCOWorldHeritageSiteoffthecoastofnortheastAustralia,is344,400 squarekilometers(133,000squaremiles). TheGreatBarrierReefandtheNewCaledoniaBarrierReefareunderwater hotspotsforbiodiversity.TheGreatBarrierReefishometo30speciesof 5of9 whales,dolphins,andporpoises;sixspeciesofseaturtles;215speciesofbirds; andmorethan1,500speciesoffish.TheNewCaledoniaBarrierReefishometo 600speciesofsponges,5,500speciesofmollusks,5,000speciesof crustaceans,andatleast1,000speciesoffish. TheEasternIndo-Pacificrealmsurroundsthetropicalislandsofthecentral PacificOcean,extendingfromtheMarshallIslandsthroughcentraland southeasternPolynesia.LiketheCentralIndo-Pacificrealm,thisrealmisalso knownforitstropicalcoralformations.Avarietyofwhale,tortoise,andfish speciesalsoinhabitthisrealm. Vocabulary Term Partof Definition Speech ancestor noun arid adjectivedry. atoll noun biodiversity noun continent noun continental island convergent plateboundary noun noun coral noun coralreef noun crust noun current noun organismfromwhomoneisdescended. acoralreeforstringofcoralislandsthatsurroundsa lagoon. allthedifferentkindsoflivingorganismswithinagiven area. oneofthesevenmainlandmassesonEarth. landonceconnectedtoacontinentbutbrokenoffby shiftingtectonicplates. areawheretwoormoretectonicplatesbumpintoeach other.Alsocalledacollisionzone. tinyoceananimal,someofwhichsecretecalcium carbonatetoformreefs. rockyoceanfeaturesmadeupofmillionsofcoral skeletons. rockyoutermostlayerofEarthorotherplanet. steady,predictableflowoffluidwithinalargerbodyof thatfluid. 6of9 Term Partof Definition Speech areaoflandthatreceivesnomorethan25centimeters desert noun elevation noun endemic adjectivenativetoaspecificgeographicspace. environment noun Equator noun erode verb towearaway. evolution noun changeinheritabletraitsofapopulationovertime. fauna noun animalsassociatedwithanareaortimeperiod. flora noun plantsassociatedwithanareaortimeperiod. foldmountain noun glacialperiod noun (10inches)ofprecipitationayear. heightaboveorbelowsealevel. conditionsthatsurroundandinfluenceanorganismor community. imaginarylinearoundtheEarth,anotherplanet,orstar runningeast-west,0degreeslatitude. areasoftheEarth'scrustthathavebeenbentand forcedupbymovementoftectonicplates. timeoflong-termloweringoftemperaturesonEarth. Alsoknownasaniceage. glacier noun massoficethatmovesslowlyoverland. highisland noun anoceanicorvolcanicisland. human geography island noun noun thestudyofthewayhumancommunitiesandsystems interactwiththeirenvironment. bodyoflandsurroundedbywater. shallowbodyofwaterthatmayhaveanopeningtoa lagoon noun largerbodyofwater,butisalsoprotectedfromitbya sandbarorcoralreef. landscape noun thegeographicfeaturesofaregion. lowisland noun continentalisland. magma noun marine adjectivehavingtodowiththeocean. molten,orpartiallymelted,rockbeneaththeEarth's surface. 7of9 Term Partof marinerealm noun marsupial noun microcontinentnoun monotreme mountain range Definition Speech noun noun largeoceanregion,includingitsunderwaterlandscape, climate,andorganisms. mammalthatcarriesitsyounginapouchonthe mother'sbody. atypeoflargecontinentalisland. typeofmammalsthatlayeggsinsteadofgivingbirthto liveyoung. seriesorchainofmountainsthatareclosetogether. substanceanorganismneedsforenergy,growth,and nutrient noun Oceania noun regionincludingislandgroupsintheSouthPacific. Outback noun remote,sparselypopulatedinteriorregionofAustralia. noun studyofthenaturalfeaturesandprocessesoftheEarth. plain noun flat,smoothareaatalowelevation. predator noun animalthathuntsotheranimalsforfood. rainforest noun resource noun RingofFire noun physical geography life. areaoftall,mostlyevergreentreesandahighamount ofrainfall. availablesupplyofmaterials,goods,orservices. Resourcescanbenaturalorhuman. horseshoe-shapedstringofvolcanoesandearthquake sitesaroundedgesofthePacificOcean. baselevelformeasuringelevations.Sealevelis sealevel noun determinedbymeasurementstakenovera19-year cycle. tectonic activity noun movementoftectonicplatesresultingingeologic activitysuchasvolcaniceruptionsandearthquakes. 8of9 Term Partof Definition Speech existinginthetropics,thelatitudesbetweentheTropic tropical adjectiveofCancerinthenorthandtheTropicofCapricorninthe south. theUnitedNationsEducational,Scientific,andCultural UNESCO noun unique adjectiveoneofakind. valley noun volcano noun Organization. depressionintheEarthbetweenhills. anopeningintheEarth'scrust,throughwhichlava,ash, andgaseserupt,andalsotheconebuiltbyeruptions. amicrocontinentthatbrokeofffromAustraliaabout80 Zealandia noun millionyearsago.Zealandiaisalmosttotally underwater. Articles&Profiles NationalGeographicMagazine:Australia’sMonsoon NationalGeographicMagazine:Murray-DarlingBasin—Australia’sDryRun Maps NationalGeographicEvents:GiantTravelingMapofthePacificOcean Websites TheEncyclopediaofNewZealand:Deep-SeaCreatures NationalGeographicTravel:AustraliaandOceania ©1996–2017NationalGeographicSociety.Allrightsreserved. 9of9