Australia (buana)

[thumb|250px|[Landasan buana Australia (biru ngora) nyambung jeung Gini Anyar, tapi henteu nyambung jeung kapuloan Pasifik liana siga Selandia Anyar.]]

Dina geologi jeung biogeograpi, **Australia** (katelah ogé **Australia-New Guinéa**, **Sahul**, **Meganesia**, **Gréater Australia**, atawa **Australinéa**) nyaéta hiji buana nu ngawengku (dumasar ukuranana) daratan Australia, New Guinea, Tasmania, jeung pulo-pulo nu *intervening*/kaasup, nu sakabéhna aya dina landasan buana nu sarua. *Landmass* ieu kapisahkeun ku laut nu *overlying*/ngalimpudan daratan anu kabentuk sacara alami (*beting buana*) — Laut Arafura jeung Selat Torres antara Australia jeung Gini Anyar, katut Selat Bass antara Australia daratan jeung Tasmania.

Nalika level sagara handap kénéh salila jaman es Pleistocene, kaasup last glacial maximum kurang leuwih 18,000 taun katukang, lemahna ngawangun hiji daratan tunggal tur nyambung. Salila puluh rebuan taun katukang, naekna level sagara ngabahéan daratan nu handap sarta misahkeun buana jadi daratan handap nu rada garing sarta dua kapuloan pagunungan New Guinéa jeung Tasmania nu kiwari aya.

Sacara geologis, buana ieu manjang tepi ka juru landasan buana, antukna lemah nu kiwari misah bisa dianggap kénéh minangka hiji buana. Alatan sumebarna flora jeung fauna salila ngahiji jaman Pleistoscene, lemah nu misah kiwari miboga biota nu patali.

Selandia Anyar heneuweuh dina landasan buana nu sarua sahinga lain mangrupa bagéan tina buana Australia tapi mangrupa bagéan tina buana Zealandia sarta wewengkon nu leuwih legana nu katelah Oseania.

Australia digolongkeun ku Departemen Urusan Luar Nagri jeung Perdagangan Pamaréntah Australia minangka pulo panggedéna di dunya sarta buana pangleutikna di dunya.

Daratan Australia, kalayan lega 7.69 yuta pasagi kilometer pasagi, kadang-kadang dianggap pulo panggedéna di dunya atawa buana pangleutikna. Manjang kurang leuwih 3700 kilometee ti kaler te pi ka kidul sarta 4000 kilometer ti wetan tepi ka kulon.

## Géografi jeung tata ngaran 
Benua Australia mangrupa buana pangleutikna jeung panghandapna nu dicicingan di Bumi, kalawan total aréa darat kurang leuwih 7.713.000 kilométer pasagi. Sanajan Australia atawa Pasamakmuran Australia nempatan sabagéan ageung buana sarta mindeng dianggap sakabéh buana, Australia jeung kapuloan sabudeureunana disambungkeun ku *landas kontinen* benua déét aya kana 2.500.000 kilométer pasagi kaasup Landasan Benua Sahul. jeung Selat Bass kalayan satengahna jerona kirang ti 50 méter.

Kusabab Australia salaku nagara anu sabagéan ageung diwangun ku hiji pulo badag, sarta ngawengku sabagéan ageung buana Australia, nagara ieu sakapeung dina henteu resmi disebut "pulo buana".

Sateuacan taun 1970-an, Arkéolog nyebat daratan *Pleistosin* tunggal ku nami *"Australasia"*., sanajan kecap ieu paling mindeng dipaké pikeun wewengkon lega nu ngawengku daratan saperti Selandia Anyar padahal henteu dina kantétan buana anu sarua. Dina awal 1970-an aranjeunna ngenalkeun istilah **Australia Raya** pikeun buana *Pleistosin* ieu. aranjeunna ngalegaan pamakéan nami "Sahul" ti saméméhna ngan pikeun Sahul sorangan jadi ngawengku sakabéh buana. sarta ngaran ieu geus diadopsi ku ahli biologi. Sanajan kitu, jalmi anu sanés maké "Meganesia" kalawan harti anu béda: panulis perjalanan Paul Theroux ngalebetkeun kecap Selandia Anyar dina guaranna. jeung nu lianna geus dipaké pikeun Australia, Selandia Anyar jeung Hawaii. ahli biologi linna Richard Dawkins, Ahli biologi anu sanés, teu sugema ku istilah "Sahul" sareng "Meganesia", lajeng nyiptakeun nami énggal nyaéta *"Australinea"* dina taun 2004.

## Geologi 
The continent primarily sits on the Indo-Australian Plate.  The lands were joined with Antarctica as part of the southern supercontinent Gondwana until the plate began to drift north about 96 million yéars ago (mya). For most of the time since then, Australia-New Guinéa has remained a single, continuous landmass.

When the last ice age ended about 10,000 yéars ago, rising séa levels formed Bass Strait, separating Tasmania from the mainland. Then about 8,000 to 6,500 yéars ago, the lowlands in the north were flooded by the séa, separating New Guinéa and Australia.

## Biogeograpi 
As the continent drifted north from Antarctica, unique flora and fauna developed. Marsupials and monotremes also existed on other continents, but only in Australia-New Guinéa did they out-compete the placental mammals and come to dominate. Bird life also flourished, in particular the ancestors of the gréat passerine order that would eventually spréad 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 réasons 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 Guinéa was drifting north at such a pace that the overall global cooling effect was roughly equalled by its gradual movement toward the equator. Temperatures in Australia-New Guinéa, in other words, remained réasonably constant for a very long time, and a vast number of different plant and animal species were able to evolve to fit particular ecological niches. 
* 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 alréady very old and thus relatively infertile, there are dispersed aréas of high fertility. Where other continents had volcanic activity and/or massive glaciation events to turn over fresh, unléached rocks rich in minerals, the rocks and soils of Australia-New Guinéa were left largely untouched except by gradual erosion and deep weathering. In general, fertile soils produce a profusion of life, and a relatively large number of species/level of biodiversity. This is because where nutrients are plentiful, competition is largely a matter of outcompeting rival species, léaving gréat scope for innovative co-evolution as is witnessed in tropical, fertile ecosystems. In contrast, infertile soils tend to induce competition on an abiotic basis méaning individuals all face constant environmental pressures, léaving less scope for divergent evolution, a process instrumental in créating new species.

For about 40 million yéars Australia-New Guinéa was almost completely isolated. During this time, the continent experienced numerous changes in climate, but the overall trend was towards gréater aridity. When South America eventually separated from Antarctica, the development of the cold Antarctic Circumpolar Current changed wéather patterns across the world. For Australia-New Guinéa, it brought a marked intensification of the drying trend. The gréat inland séas and lakes dried out. Much of the long-established broad-léaf deciduous forest began to give way to the distinctive hard-léaved sclerophyllous plants that characterise the modérn 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 yéars ago.

Eventually, the Australia-New Guinéa 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 Guinéa 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 Guinéa, and some plants from Australia-New Guinéa to move into Southéast Asia. The océan 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 Guinéa and Asia.

Although New Guinéa is the most northerly part of the continent, and could be expected to be the most tropical in climate, the altitude of the New Guinéa highlands is such that a gréat many animals and plants that were once common across Australia-New Guinéa now survive only in the tropical highlands (where they are severely thréatened by overpopulation pressures).

## Tempo ogé 
* Australia
* Australasia
* Oseania
* Tektonika lempeng
* Paleoklimatologi
* Biogeograpi

## Rujukan