of the continent The Australian continent, as a whole being part of the
Australian Plate, is the lowest, flattest, and oldest landmass on Earth and it has had a relatively stable geological history.
New Zealand is not part of the continent of Australia, but of the separate, submerged continent of
Zealandia. New Zealand and Australia are both part of the Oceanian sub-region known as
Australasia, with New Guinea being in
Melanesia. The continent includes a continental shelf overlain by shallow seas which divide it into several landmasses—the
Arafura Sea and
Torres Strait between mainland Australia and New Guinea, and
Bass Strait between mainland Australia and Tasmania. When
sea levels were lower during the
Pleistocene ice age, including the
Last Glacial Maximum about 18,000 BC, they were connected by dry land. During the past 18,000 to 10,000 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. The
continental shelf connecting the islands, half of which is less than deep, covers some , including the
Sahul Shelf and
Bass Strait. Geological forces such as
tectonic uplift of mountain ranges or clashes between tectonic plates occurred mainly in Australia's early history, when it was still a part of
Gondwana. Australia is situated in the middle of the tectonic plate, and therefore currently has no active volcanism. since the
Last Glacial Maximum The continent primarily sits on the Indo-Australian Plate. Because of its central location on its tectonic plate, Australia does not have any active volcanic regions, the only continent with this distinction. 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. For most of the time since then, Australia–New Guinea remained a continuous landmass. When the
last glacial period 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 the
Aru Islands, mainland Australia,
New Guinea, and Tasmania. A northern arc consisting of the
New Guinea Highlands, the
Raja Ampat Islands, and
Halmahera was uplifted by the northward migration of Australia and subduction of the
Pacific Plate. The
Outer Banda Arc was accreted along the northwestern edge the continent; it includes the islands of
Timor,
Tanimbar, and
Seram. Papua New Guinea has
several volcanoes, as it is situated along the
Pacific Ring of Fire. Volcanic eruptions are not rare, and the area is prone to
earthquakes and
tsunamis because of this.
Mount Wilhelm in Papua New Guinea is the second highest mountain in the continent, and at
above sea level,
Puncak Jaya is the
highest mountain.
Ecology Flora in the
New Guinea Highlands 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. Typical Southern Hemisphere flora include the
conifers
Podocarpus (eastern Australia and New Guinea), the rainforest emergents
Araucaria (eastern Australia and New Guinea),
Nothofagus (New Guinea and
Tasmania) and
Agathis (northern
Queensland and New Guinea), as well as
tree ferns and several species of
Eucalyptus. Prominent features of the Australian flora are adaptations to
aridity and fire which include
scleromorphy and
serotiny. These adaptations are common in species from the large and well-known families
Proteaceae (
Banksias and
Grevilleas),
Myrtaceae (
Eucalyptus or gum trees,
Melaleucas and
Callistemons),
Fabaceae (
Acacias or wattles), and
Casuarinaceae (
Casuarinas or she-oaks), which are typically found in the Australian mainland. The flora of New Guinea is a mixture of many
tropical rainforest species with origins in Asia, such as
Castanopsis acuminatissima, Lithocarpus spp.,
elaeocarps, and
laurels, together with typically Australasian flora. In the New Guinean highlands, conifers such as
Dacrycarpus, Dacrydium, Papuacedrus and
Libocedrus are present. 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. Among the fungi, the remarkable association between
Cyttaria gunnii (one of the "golf-ball" fungi) and its associated trees in the genus
Nothofagus is evidence of that drift: the only other places where this association is known are New Zealand and southern
Argentina and
Chile.
Fauna Due to the spread of animals, fungi and plants across the single Pleistocene landmass the separate lands have a related
biota. There are over 300 bird species in
West Papua, of which at least 20 are unique to the ecoregion, and some live only in very restricted areas. These include the
grey-banded munia,
Vogelkop bowerbird, and the
king bird-of-paradise. Australia has a huge variety of animals; some 83% of
mammals, 89% of
reptiles, 24% of fish and insects and 93% of
amphibians that inhabit the continent are
endemic to Australia. This high level of endemism can be attributed to the continent's long geographic isolation,
tectonic stability, and the effects of an unusual pattern of climate change on the soil and
flora over geological time. Australia and its territories are home to around 800 species of bird; 45% of these are endemic to Australia. Predominant bird species in Australia include the
Australian magpie,
Australian raven, the
pied currawong,
crested pigeons and the
laughing kookaburra. The
koala,
emu,
platypus and
kangaroo are
national animals of Australia, and the
Tasmanian devil is also one of the well-known animals in the country. The
goanna is a
predatory lizard native to the
Australian mainland. As the continent drifted north from Antarctica, a unique
fauna,
flora and
mycobiota developed.
Marsupials and
monotremes also existed on other continents, but only in Australia–New Guinea did they out-compete the
placental mammals and come to dominate. New Guinea has 284 species and six orders of mammals: monotremes, three orders of marsupials,
rodents and
bats; 195 of the mammal species (69%) are endemic. New Guinea has a rich diversity of
coral life and 1,200 species of
fish have been found. Also about 600 species of reef-building coral—the latter equal to 75 percent of the world's known total. New Guinea has 578 species of breeding birds, of which 324 species are endemic.
Bird life also flourished—in particular, the
songbirds (order
Passeriformes, suborder Passeri) are thought to have evolved 50 million years ago in the part of
Gondwana that later became
Australia, New Zealand,
New Guinea, and
Antarctica, before radiating into a great number of different forms and then spreading around the globe. Animal groups such as
macropods,
monotremes, and
cassowaries are endemic to Australia. There were three main reasons for the enormous diversity that developed in animal, fungal and plant 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
equator.
Temperatures in Australia–New Guinea, in other words, remained reasonably constant for a very long time, and a vast number of different animal, fungal and plant 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 already very old and thus relatively infertile, there are dispersed areas of high fertility. Where other continents had
volcanic activity and/or massive
glaciation events to turn over fresh, unleached
rocks rich in
minerals, the rocks and
soils of Australia–New Guinea 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, leaving great scope for innovative
co-evolution 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. 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
population growth.
Climate In New Guinea, the climate is mostly
monsoonal (December to March), southeast monsoon (May to October), and
tropical rainforest with slight seasonal temperature variation. In lower altitudes, the temperature is around year round. But the higher altitudes, such as
Mendi, are constantly around with cool lows nearing , with abundant rainfall and high humidity. The
New Guinea Highlands are one of the few regions close to the
equator that experience
snowfall, which occurs in the most elevated parts of the mainland. Some areas in the island experience an extraordinary amount of precipitation, averaging roughly of rainfall annually. The Australian landmass's climate is mostly
desert or
semi-arid, with the southern coastal corners having a
temperate climate, such as
oceanic and
humid subtropical climate in the east coast and
Mediterranean climate in the west. The northern parts of the country have a
tropical climate.
Snow falls frequently on the
highlands near the east coast, in the states of
Victoria,
New South Wales,
Tasmania and in the
Australian Capital Territory. Temperatures in Australia have ranged from above to well below . Nonetheless, minimum temperatures are moderated. The
El Niño-Southern Oscillation is associated with seasonal abnormality in many areas in the world. Australia is one of the continents most affected and experiences
extensive droughts alongside considerable wet periods. {{Gallery ==Politics==