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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
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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
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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
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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.)
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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
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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.
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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.
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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.
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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.
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