Australia (buana)

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.
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. Lajeng dina konferénsi di 1975 sarta publikasi saterusna, aranjeunna ngalegaan pamakéan nami "Sahul" ti saméméhna ngan pikeun Sahul sorangan jadi ngawengku sakabéh buana. Ahli biologi, anu henteu terang istilah anu dianggo ku arkéolog, dina taun 1984 ngusulkeun nami "Meganesia", hartosna "pulo ageung" atanapi "grup pulo ageung ", pikeun dilarapkeun ka buana Pleistosin sareng daratan anu kiwari. 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.
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.
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.
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).