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, nu sakabéhna aya dina landasan buana nu sarua. Landmass ieu kapisahkeun ku laut nu overlying 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.

Geograpi jeung tata ngaran 

The Australian continent is the smallest and lowest-lying human-inhabited continent on Earth, having a total land aréa of some 7,713,000 square kilometres.  Though the Commonwealth of Australia occupies much of the continent and is often mistaken for being the entire continent, Australia and adjacent islands are connected by a shallow continental shelf covering some 2,500,000 square kilometres including the Sahul Shelf and Bass Strait and half of which is less than 50 metres deep.

As Australia the country is largely a single island, and comprises most of Australia the continent, it is sometimes informally referred to as "the island continent".

Prior to the 1970s, archaéologists called the single Pleistocene landmass by the name Australasia, although this word is most often used for a wider region that includes lands like New Zéaland that are not on the same continental shelf. In the éarly 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. A biologist, unaware of the terms used by archaéologists, suggested in 1984 the name Meganesia, méaning "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. However, others have used Meganesia with different méanings: travel writer Paul Theroux included New Zéaland in his definition and others have used it for Australia, New Zéaland and Hawaii. Another biologist, Richard Dawkins, unimpressed with Sahul and Meganesia, coined the name Australinea in 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 

Buana
Wangun taneuh di Australia
Wangun taneuh di Oséania
Gini Anyar
Sajarah alam Australia