.gif)
Australia (continent)
Encyclopedia
Australia is the world's smallest continent
, comprising the mainland of Australia
and proximate island
s including Tasmania
, New Guinea
, the Aru Islands
and Raja Ampat Islands
. Australia and these nearby islands, all part of the same geological landmass, are separated by seas overlying the continental shelf — the Arafura Sea
and Torres Strait
between Australia and New Guinea, and Bass Strait
between mainland Australia and Tasmania.
When sea level
s were lower during the Pleistocene ice age
, including the last glacial maximum
about 18,000 BC, the lands formed a single, continuous landmass
. During the past ten thousand years, rising sea levels overflowed the lowlands and separated the continent into today's low-lying arid
to semi-arid
mainland and the two mountainous islands of New Guinea and Tasmania.
Geologically, the continent extends to the edge of the continental shelf, so the now-separate lands can still be considered a continent. Due to the spread of flora and fauna across the single Pleistocene landmass the separate lands have a related biota
.
New Zealand
is not on the same continental shelf
and so is not part of the continent of Australia but is part of the submerged continent Zealandia
. Zealandia and Australia together are part of the wider region known as Oceania
or Australasia
. Australia is sometimes known in technical contexts by the names Sahul, Australinea and Meganesia.
The Australian continent is the smallest and lowest-lying human-inhabited continent on Earth
, having a total land area of some 8,560,000 square kilometres (3,305,000 sq. mi.). The continental shelf
connecting the islands, half of which is less than 50 metres deep covers some 2,500,000 square kilometres, including the Sahul Shelf
and Bass Strait
.
As the country of Australia is mostly on a single landmass, and comprises most of the continent, it is sometimes informally referred to as an "island" continent, surrounded by oceans.
Prior to the 1970s, archaeologists called the single Pleistocene landmass by the name Australasia, derived from the Latin
australis, meaning "southern", although this word is most often used for a wider region that includes lands like New Zealand that are not on the same continental shelf.
In the early 1970s they introduced the term Greater Australia for the Pleistocene continent. Then at a 1975 conference and consequent publication, they extended the name Sahul from its previous use for just the Sahul Shelf
to cover the continent.
Biologists suggested in 1984 the name Meganesia, meaning "great island" or "great island-group", applying it to both the Pleistocene continent and the present-day lands, and this name has been taken up by biologists. Others have used Meganesia with different meanings: travel writer Paul Theroux
included New Zealand in his definition and others have used it for Australia, New Zealand and Hawaii
. Another biologist, Richard Dawkins
coined the name Australinea in 2004. Australia-New Guinea has also been used.
. The lands were joined with Antarctica as part of the southern supercontinent Gondwana
until the plate began to drift north about 96 million years ago (mya). For most of the time since then, Australia-New Guinea has remained a single, continuous landmass. When the last ice age
ended in about 10,000 BC, rising sea levels formed Bass Strait, separating Tasmania from the mainland. Then between about 8,000 and 6,500 BC, the lowlands in the north were flooded by the sea, separating New Guinea and Australia.
s and monotreme
s also existed on other continents, but only in Australia-New Guinea did they out-compete the placental mammals and come to dominate. Bird life also flourished, in particular the ancestors of the great passerine
order that would eventually spread to all parts of the globe and account for more than half of all living avian species
.
Animal groups such as macropods, monotremes, and cassowaries
are endemic to Australia. There were three main reasons for the enormous diversity that developed in both plant and animal life.
For about 40 million years Australia-New Guinea was almost completely isolated. During this time, the continent experienced numerous changes in climate, but the overall trend was towards greater aridity. When South America
eventually separated from Antarctica, the development of the cold Antarctic Circumpolar Current
changed weather patterns across the world. For Australia-New Guinea, it brought a marked intensification of the drying trend. The great inland seas and lakes dried out. Much of the long-established broad-leaf deciduous
forest began to give way to the distinctive hard-leaved sclerophyllous plants that characterise the modern Australian landscape.
For many species, the primary refuge was the relatively cool and well-watered Great Dividing Range
. Even today, pockets of remnant vegetation remain in the cool uplands, some species not much changed from the Gondwanan forms of 60 or 90 million years ago.
Eventually, the Australia-New Guinea tectonic plate collided with the Eurasian plate
to the north. The collision caused the northern part of the continent to buckle upwards, forming the high and rugged mountains of New Guinea and, by reverse (downwards) buckling, the Torres Strait
that now separates the two main landmasses. The collision also pushed up the islands of Wallacea
, which served as island 'stepping-stones' that allowed plants from Southeast Asia
's rainforests to colonise New Guinea, and some plants from Australia-New Guinea to move into Southeast Asia. The ocean straits between the islands were narrow enough to allow plant dispersal, but served as an effective barrier to exchange of land mammals between Australia-New Guinea and Asia.
Although New Guinea is the most northerly part of the continent, and could be expected to be the most tropical in climate, the altitude of the New Guinea highlands is such that a great many animals and plants that were once common across Australia-New Guinea now survive only in the tropical highlands (where they are severely threatened by overpopulation
pressures).
Continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
, comprising the mainland of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and proximate island
Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
s including Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
, New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
, the Aru Islands
Aru Islands
The Aru Islands are a group of about ninety-five low-lying islands in the Maluku province of eastern Indonesia. They also form a regency of Indonesia.-Geography:...
and Raja Ampat Islands
Raja Ampat Islands
Located off the northwest tip of Bird's Head Peninsula on the island of New Guinea, in Indonesia's West Papua province, Raja Ampat, or the Four Kings, is an archipelago comprising over 1,500 small islands, cays and shoals surrounding the four main islands of Misool, Salawati, Batanta and Waigeo,...
. Australia and these nearby islands, all part of the same geological landmass, are separated by seas overlying the continental shelf — the Arafura Sea
Arafura Sea
The Arafura Sea lies west of the Pacific Ocean overlying the continental shelf between Australia and New Guinea.-Geography:The Arafura Sea is bordered by Torres Strait and through that the Coral Sea to the east, the Gulf of Carpentaria to the south, the Timor Sea to the west and the Banda and Ceram...
and Torres Strait
Torres Strait
The Torres Strait is a body of water which lies between Australia and the Melanesian island of New Guinea. It is approximately wide at its narrowest extent. To the south is Cape York Peninsula, the northernmost continental extremity of the Australian state of Queensland...
between Australia and New Guinea, and Bass Strait
Bass Strait
Bass Strait is a sea strait separating Tasmania from the south of the Australian mainland, specifically the state of Victoria.-Extent:The International Hydrographic Organization defines the limits of the Bass Strait as follows:...
between mainland Australia and Tasmania.
When sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
s were lower during the Pleistocene ice age
Quaternary glaciation
Quaternary glaciation, also known as the Pleistocene glaciation, the current ice age or simply the ice age, refers to the period of the last few million years in which permanent ice sheets were established in Antarctica and perhaps Greenland, and fluctuating ice sheets have occurred elsewhere...
, including the last glacial maximum
Last Glacial Maximum
The Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and...
about 18,000 BC, the lands formed a single, continuous landmass
Landmass
A landmass is a contiguous area of land surrounded by ocean. Although it may be most often written as one word to distinguish it from the usage "land mass"—the measure of land area—it is also used as two words.Landmasses include:*supercontinents...
. During the past ten thousand years, rising sea levels overflowed the lowlands and separated the continent into today's low-lying arid
Arid
A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...
to semi-arid
Semi-arid
A semi-arid climate or steppe climate describes climatic regions that receive precipitation below potential evapotranspiration, but not extremely...
mainland and the two mountainous islands of New Guinea and Tasmania.
Geologically, the continent extends to the edge of the continental shelf, so the now-separate lands can still be considered a continent. Due to the spread of flora and fauna across the single Pleistocene landmass the separate lands have a related biota
Biota (ecology)
Biota are the total collection of organisms of a geographic region or a time period, from local geographic scales and instantaneous temporal scales all the way up to whole-planet and whole-timescale spatiotemporal scales. The biota of the Earth lives in the biosphere.-See...
.
New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
is not on the same continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
and so is not part of the continent of Australia but is part of the submerged continent Zealandia
Zealandia (continent)
Zealandia , also known as Tasmantis or the New Zealand continent, is a nearly submerged continental fragment that sank after breaking away from Australia 60–85 million years ago, having separated from Antarctica between 85 and 130 million years ago...
. Zealandia and Australia together are part of the wider region known as Oceania
Oceania
Oceania is a region centered on the islands of the tropical Pacific Ocean. Conceptions of what constitutes Oceania range from the coral atolls and volcanic islands of the South Pacific to the entire insular region between Asia and the Americas, including Australasia and the Malay Archipelago...
or Australasia
Australasia
Australasia is a region of Oceania comprising Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes...
. Australia is sometimes known in technical contexts by the names Sahul, Australinea and Meganesia.
Geography and nomenclature
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, having a total land area of some 8,560,000 square kilometres (3,305,000 sq. mi.). The continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
connecting the islands, half of which is less than 50 metres deep covers some 2,500,000 square kilometres, including the Sahul Shelf
Sahul Shelf
The Sahul Shelf is part of the continental shelf of Sahul and lies off the coast of Australia. The Sahul Shelf proper stretches northwest from Australia much of the way under the Timor Sea towards Timor, ending where the seabed begins descending into the Timor Trough...
and Bass Strait
Bass Strait
Bass Strait is a sea strait separating Tasmania from the south of the Australian mainland, specifically the state of Victoria.-Extent:The International Hydrographic Organization defines the limits of the Bass Strait as follows:...
.
As the country of Australia is mostly on a single landmass, and comprises most of the continent, it is sometimes informally referred to as an "island" continent, surrounded by oceans.
Prior to the 1970s, archaeologists called the single Pleistocene landmass by the name Australasia, derived from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
australis, meaning "southern", although this word is most often used for a wider region that includes lands like New Zealand that are not on the same continental shelf.
In the early 1970s they introduced the term Greater Australia for the Pleistocene continent. Then at a 1975 conference and consequent publication, they extended the name Sahul from its previous use for just the Sahul Shelf
Sahul Shelf
The Sahul Shelf is part of the continental shelf of Sahul and lies off the coast of Australia. The Sahul Shelf proper stretches northwest from Australia much of the way under the Timor Sea towards Timor, ending where the seabed begins descending into the Timor Trough...
to cover the continent.
Biologists suggested in 1984 the name Meganesia, meaning "great island" or "great island-group", applying it to both the Pleistocene continent and the present-day lands, and this name has been taken up by biologists. Others have used Meganesia with different meanings: travel writer Paul Theroux
Paul Theroux
Paul Edward Theroux is an American travel writer and novelist, whose best known work of travel writing is perhaps The Great Railway Bazaar . He has also published numerous works of fiction, some of which were made into feature films. He was awarded the 1981 James Tait Black Memorial Prize for his...
included New Zealand in his definition and others have used it for Australia, New Zealand and Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
. Another biologist, Richard Dawkins
Richard Dawkins
Clinton Richard Dawkins, FRS, FRSL , known as Richard Dawkins, is a British ethologist, evolutionary biologist and author...
coined the name Australinea in 2004. Australia-New Guinea has also been used.
Geology
The continent primarily sits on the Indo-Australian PlateIndo-Australian Plate
The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters...
. The lands were joined with Antarctica as part of the southern supercontinent Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
until the plate began to drift north about 96 million years ago (mya). For most of the time since then, Australia-New Guinea has remained a single, continuous landmass. When the last ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
ended in about 10,000 BC, rising sea levels formed Bass Strait, separating Tasmania from the mainland. Then between about 8,000 and 6,500 BC, the lowlands in the north were flooded by the sea, separating New Guinea and Australia.
Biogeography
As the continent drifted north from Antarctica, unique flora and fauna developed. MarsupialMarsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
s and monotreme
Monotreme
Monotremes are mammals that lay eggs instead of giving birth to live young like marsupials and placental mammals...
s also existed on other continents, but only in Australia-New Guinea did they out-compete the placental mammals and come to dominate. Bird life also flourished, in particular the ancestors of the great passerine
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
order that would eventually spread to all parts of the globe and account for more than half of all living avian species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
.
Animal groups such as macropods, monotremes, and cassowaries
Cassowary
The cassowaries are ratites, very large flightless birds in the genus Casuarius native to the tropical forests of New Guinea, nearby islands and northeastern Australia. There are three extant species recognized today...
are endemic to Australia. There were three main reasons for the enormous diversity that developed in both plant and animal life.
- While much of the rest of the world underwent significant cooling and thus loss of species diversity, Australia-New Guinea was drifting north at such a pace that the overall global cooling effect was roughly equalled by its gradual movement toward the equatorEquatorAn equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
. TemperatureTemperatureTemperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
s in Australia-New Guinea, in other words, remained reasonably constant for a very long time, and a vast number of different plant and animal species were able to evolve to fit particular ecological nicheEcological nicheIn ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...
s. - Because the continent was more isolated than any other, very few outside species arrived to colonise, and unique native forms developed unimpeded.
- Finally, despite the fact that the continent was already very old and thus relatively infertile, there are dispersed areas of high fertility. Where other continents had volcanicVolcanismVolcanism is the phenomenon connected with volcanoes and volcanic activity. It includes all phenomena resulting from and causing magma within the crust or mantle of a planet to rise through the crust and form volcanic rocks on the surface....
activity and/or massive glaciationGlacierA glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
events to turn over fresh, unleached rockRock (geology)In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...
s rich in mineralMineralA mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s, the rocks and soilSoilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
s of Australia-New Guinea were left largely untouched except by gradual erosionErosionErosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
and deep weatheringWeatheringWeathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...
. In general, fertile soils produce a profusion of life, and a relatively large number of species/level of biodiversity. This is because where nutrientNutrientA nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
s are plentiful, competition is largely a matter of outcompeting rival species, leaving great scope for innovative co-evolutionCo-evolutionIn biology, coevolution is "the change of a biological object triggered by the change of a related object." Coevolution can occur at many biological levels: it can be as microscopic as correlated mutations between amino acids in a protein, or as macroscopic as covarying traits between different...
as is witnessed in tropical, fertile ecosystems. In contrast, infertile soils tend to induce competition on an abiotic basis meaning individuals all face constant environmental pressures, leaving less scope for divergent evolution, a process instrumental in creating new species.
For about 40 million years Australia-New Guinea was almost completely isolated. During this time, the continent experienced numerous changes in climate, but the overall trend was towards greater aridity. When South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
eventually separated from Antarctica, the development of the cold Antarctic Circumpolar Current
Antarctic Circumpolar Current
The Antarctic Circumpolar Current is an ocean current that flows from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. The ACC is the dominant circulation feature of the Southern Ocean and, at approximately 125 Sverdrups, the largest ocean current...
changed weather patterns across the world. For Australia-New Guinea, it brought a marked intensification of the drying trend. The great inland seas and lakes dried out. Much of the long-established broad-leaf deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
forest began to give way to the distinctive hard-leaved sclerophyllous plants that characterise the modern Australian landscape.
For many species, the primary refuge was the relatively cool and well-watered Great Dividing Range
Great Dividing Range
The Great Dividing Range, or the Eastern Highlands, is Australia's most substantial mountain range and the third longest in the world. The range stretches more than 3,500 km from Dauan Island off the northeastern tip of Queensland, running the entire length of the eastern coastline through...
. Even today, pockets of remnant vegetation remain in the cool uplands, some species not much changed from the Gondwanan forms of 60 or 90 million years ago.
Eventually, the Australia-New Guinea tectonic plate collided with the Eurasian plate
Eurasian Plate
The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...
to the north. The collision caused the northern part of the continent to buckle upwards, forming the high and rugged mountains of New Guinea and, by reverse (downwards) buckling, the Torres Strait
Torres Strait
The Torres Strait is a body of water which lies between Australia and the Melanesian island of New Guinea. It is approximately wide at its narrowest extent. To the south is Cape York Peninsula, the northernmost continental extremity of the Australian state of Queensland...
that now separates the two main landmasses. The collision also pushed up the islands of Wallacea
Wallacea
Wallacea is a biogeographical designation for a group of Indonesian islands separated by deep water straits from the Asian and Australian continental shelves. Wallacea includes Sulawesi, the largest island in the group, as well as Lombok, Sumbawa, Flores, Sumba, Timor, Halmahera, Buru, Seram, and...
, which served as island 'stepping-stones' that allowed plants from Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
's rainforests to colonise New Guinea, and some plants from Australia-New Guinea to move into Southeast Asia. The ocean straits between the islands were narrow enough to allow plant dispersal, but served as an effective barrier to exchange of land mammals between Australia-New Guinea and Asia.
Although New Guinea is the most northerly part of the continent, and could be expected to be the most tropical in climate, the altitude of the New Guinea highlands is such that a great many animals and plants that were once common across Australia-New Guinea now survive only in the tropical highlands (where they are severely threatened by overpopulation
Overpopulation
Overpopulation is a condition where an organism's numbers exceed the carrying capacity of its habitat. The term often refers to the relationship between the human population and its environment, the Earth...
pressures).
See also
- List of basic Australia topics
- Plate tectonicsPlate tectonicsPlate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
- PaleoclimatologyPaleoclimatologyPaleoclimatology is the study of changes in climate taken on the scale of the entire history of Earth. It uses a variety of proxy methods from the Earth and life sciences to obtain data previously preserved within rocks, sediments, ice sheets, tree rings, corals, shells and microfossils; it then...
- AustralasiaAustralasiaAustralasia is a region of Oceania comprising Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes...
- OceaniaOceaniaOceania is a region centered on the islands of the tropical Pacific Ocean. Conceptions of what constitutes Oceania range from the coral atolls and volcanic islands of the South Pacific to the entire insular region between Asia and the Americas, including Australasia and the Malay Archipelago...