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Australiathe smallest continent and one of the largest countries on Earth, lying between the Pacific and Indian oceans in the Southern Hemisphere. The Australian mainland extends from west to east for nearly 2, miles 4, km and from Cape York Peninsula in the northeast to Wilsons Promontory in the southeast for nearly 2, miles 3, km. To the south, Australian jurisdiction extends a further miles km to the southern extremity of the island of Tasmaniaand in the north it extends to the southern shores of Papua New Guinea.
Lange drifting away youtube simple physical terms, the age of much of the continent is certainly impressive—most of the rocks providing the foundation of Australian landforms were formed during Precambrian and Paleozoic time some 4. Australia is the last of lands only in the sense that it was the last continent, apart from Antarctica, to be explored by Europeans.
At least 60, years before European explorers sailed into the South Pacific, the first Aboriginal explorers had arrived from Asiaand by 20, years ago they had spread throughout the mainland and its chief island outlier, Tasmania. When Captain Arthur Phillip of the British Royal Navy landed with the First Fleet at Botany Bay inlange drifting away youtube may have been betweenandAboriginals, though some estimates are much higher.
Largely nomadic hunters and gatherers, the Aboriginals had already transformed the primeval landscape, principally by the use of fire, and, contrary to common European perceptions, they had established robustsemipermanent settlements in well-favoured localities. There was, rather, a series of comparatively independent expansions from the margins of the various colonies, which were not joined in an independent federated union until The most striking characteristics of the vast country are its global isolation, its low relief, and the aridity of much of its surface.
If, like the English novelist D. Its unique flora and fauna include hundreds of kinds of eucalyptus trees and the only egg-laying mammals on Earth, lange drifting away youtube platypus and echidna. Other plants and animals associated with Australia are various acacias Acacia pycnantha [golden wattle] is the national flower and dingoes, kangaroos, koalas, and kookaburras.
Isolation is also a pronounced characteristic of much of the social landscape beyond the large coastal cities. But an equally significant feature of modern Australian society is the representation of a broad spectrum of cultures drawn from many lands, a development stemming from immigration that is transforming the strong Anglo-Celtic orientation of Australian culture.
Assimilation, of course, is seldom a quick and easy process, and minority rights, multiculturalism, and race-related issues have played a large part in contemporary Australian politics. In the late s these issues sparked a conservative backlash. Australia has a federal form of government, with a national government for the Commonwealth of Australia and individual state governments those of New South WalesVictoriaQueenslandSouth AustraliaWestern Australiaand Tasmania.
Each state has a constitution, and its government exercises a limited degree of sovereignty. There are also two internal territories: Northern Territoryestablished as a self-governing territory inand the Australian Capital Territory including the city of Canberra lange drifting away youtube, which attained self-governing status in Papua New Guinea, formerly an Australian external territory, gained its independence in Historically part of the British Empire and now a member of the CommonwealthAustralia is a relatively prosperous independent country.
Australians are in many respects fortunate in that they do not share their continent—which is only a little smaller than the United States —with any other country. Extremely remote from their traditional allies and trading partners—it is some 12, miles 19, km from Australia to Great Britain via the Indian Ocean and the Suez Canal and about 7, miles 11, km across the Pacific Ocean to the west coast of the United States—Australians have become more interested in the proximity of huge potential markets in Asia and in the highly competitive industrialized economies of ChinaJapanSouth Koreaand Taiwan.
The earliest known manifestations of the geologic record of the Australian continent are 4. Based on that and other findings, the Precambrian rocks in Australia have been determined to range in age from about 3. Ace bounty poster dcuo are succeeded by rocks of the Paleozoic Erawhich extended to about million years ago; of the Mesozoic Era lange drifting away youtube, which lasted until about 66 million years ago; and of the Cenozoic Erathe past 66 million years.
For millions lange drifting away youtube years Australia was part of the supercontinent of Pangaea and subsequently its southern segment, Gondwanaland or Gondwana.
Its separate existence was finally assured by the severing of the last connection between Tasmania and Antarctica, but it has been drifting toward the Southeast Asian landmass. As a continent, Australia thus encompasses two extremes: See also geochronology: Geologic history of the Earth.
The map of the structural features of Australia and the surrounding region shows the distribution of the main tectonic units. The primary distinction is between the plates of oceanic lithospheregenerated within the past million years by seafloor spreading at the oceanic ridges, and the continental lithosphere, accumulated over the past 4 billion years.
The lithosphere is the outer rock shell of the Earth that consists of the crust and the uppermost portion of the underlying mantle; see plate tectonics. The largest area of oldest rocks is the Western Shieldcomprising the western half of the continent, which has been eroded to a low relief. The youngest rocks are found in the growing fold belt of the Banda arcs and in New Guinea at the boundary between the Lange drifting away youtube plate and the Eurasian and Pacific plates.
Precambrian rocks occupy three tectonic environments. The first is lange drifting away youtube shields, such as the Yilgarn and Pilbara blocks of the Western Shield, enclosed by later orogenic mountain belts. The second is as the basement lange drifting away youtube a younger cover of Phanerozoic sediment deposited during the past million years ; for example, all the sedimentary basins west of the Tasman Line are underlain by Precambrian basement.
The third is as relicts in younger orogenic belts, as in the Georgetown Inlier of northern Queensland and in the western half of Tasmania.
Rocks of Paleozoic age occur either in flat-lying sedimentary basins, such as the Canning Basinor within belts, such as the east—west-trending Amadeus Transverse Zone and north-trending Tasman Fold Belt. Mesozoic and Cenozoic rocks occur lange drifting away youtube widely distributed though poorly exposed basins onshore the Great Artesian Basin in the eastern centre. The geologic development may be summarized as follows. Archean rocks those more than 2. Individual blocks of Archean rocks became embedded in Proterozoic fold belts those from about 2.
The lines of weakness within the mosaic later guided stresses that pulled the blocks apart or pushed them together. The Proterozoic fold belts that bounded the western and southern sides of the Archean Yilgarn block, for example, became the lange drifting away youtube of the continental margin during seafloor spreading in the Mesozoic, and the fold belts of the Amadeus Lange drifting away youtube Zone in central Australia guided the overthrusting of blocks in the north over those in the south during the late Paleozoic.
Proterozoic Australia was part of the supercontinent of Gondwanalandcomprising India and the other southern continents, from about million years ago.
At the beginning of the Paleozoic, multi ping tool ware s million years ago, pieces began to flake off the Australian portion of Gondwanaland when ocean basins opened around its periphery. Off the northwest, an ancient forebear of the Indian Oceancalled the Tethystransferred continental terranes fault-bounded tinder app wont ipad of the crust from Gondwanaland to Asia; later generations of that ocean rifted material northward, including the biggest and latest terrane of India.
Off the east, an ancient Pacific Ocean opened and closed in the lange drifting away youtube of a series of back-arc basins or marginal seas that persists to the present. The structure of Australia was determined lange drifting away youtube the following: Australia ultimately became isolated from its Gondwanaland neighbours India and Antarctica by seafloor spreading.
Today, Australia is drifting northward from Antarctica as a result of seafloor spreading in the southeast Indian Ocean and, consequently, is colliding with the westward-moving Pacific Plate to form the strike-slip ranges of New Guinea and the S-shaped fold of the Banda arcs. This major period of geologic time can be subdivided into the older Archean and the lange drifting away youtube Proterozoic eons, the time boundary between them being some 2. In Australia the main outcrop of the Archean and older Proterozoic rocks is in the Yilgarn and Pilbara blocks of the southwest and northwest, respectively.
In the Yilgarn block the oldest known rocks are sialic crust i. The older end of that time span is provided by detrital zircon grains found in younger metasedimentary rock metamorphosed sedimentary rock some 3.
A zircon grain imbedded in 3. The younger end of 3. Subsequent to such igneous rocks being formed, siliceous sedimentary rocks were deposited during an interval of subdued relief and extensive sheets of vein quartz pebbles were concentrated on the surface.
The oldest rocks in the Pilbara block to the north make up a granite-greenstone terrane and so differ distinctly from those of the Yilgarn block. They are mostly 3. The association of basic and acid rocks suggests the possibility that older sialic crust melted. Chert within basalt 3.
Between 3. Between 2. Finally, between 2. Iron ores of hematite and goethite have been formed by supergene enrichment of banded-iron formation. The Yilgarn block became an internally coherent mass only after greenstone and associated granitic terrane had developed from 3. Mafic and ultramafic rocks those composed primarily of ferromagnesian—dark-coloured—minerals 2. Slightly older 2.
The Pilbara and Yilgarn blocks were joined between 2. Later in the Proterozoic, between 1. That view contrasts with another interpretation that regards most of the western part of Australia as intact since Archean times and considers that most later orogenic activity was ensialic. The development of the late Proterozoic Adelaidean province, the other Precambrian succession to be described here, was within a sialic basement. The Adelaidean succession crops out in the region of South Australia between Adelaide and the Flinders Ranges and contains an almost complete sedimentary record of the late Proterozoic.
The early Adelaidean Callanna and Burra groups are confined to troughs faulted down into basement. A sheet of sedimentary deposits at the base of the Callanna group was cut by faults into rift valleys that filled with basic volcanic rocks and evaporitic sediment and carbonate rock.
The succeeding Burra group comprises fluvial sediment followed by shallow marine carbonate. The late Adelaidean Umberatana and Wilpena groups unconformably succeed older rocks. The Umberatana group contains a rich record of two glaciations: The Wilpena group comprises extensive sheets of interbedded sandstonesiltstoneand shale deposited during two lange drifting away youtube transgressions, during the second dil awaiz pareshan song mp3 which deep canyons were cut and filled.
The uppermost part of the Wilpena group, in the latest Proterozoic, contains the celebrated Ediacara assemblage of the oldest well-known animal fossils. The Precambrian rocks of Australia provide a rich source of economically important minerals, such as the above-mentioned major iron ore deposits of the Pilbara block and the gold and nickel jung chang wild swans of the Yilgarn block.
Other minerals include diamonds lange drifting away youtube the Argyle diatreme vertical volcanic conduit filled with breccia in northern Western Australia. Phanerozoic Australia is divided at the Tasman Line into two parts. Those are a western terrane of exposed Precambrian blocks and fold belts overlain by thin Phanerozoic basins and an eastern terrane of exposed Phanerozoic fold belts and basins. During Phanerozoic times, Australia has been marked by three regimes: Uluru to million years agoInnamincka to 97 million years agoand Potoroo the past 97 million years.
Each regime, a complex of uniform plate-tectonic and paleoclimatic events at a similar or slowly changing latitudegenerated a depositional sequence of distinct facies separated by gaps in deposition. The Paleozoic Era about to million years ago opened in Australia with the breakup of the Precambrian continent along the Tasman Line and the initial generation of the floor of the Paleo Pacific Ocean by seafloor spreading.
In the Adelaide area, wedges of deepwater quartzose sediment advanced over the newly formed seafloor. On the northwestern side of Australia, widespread basalt erupted over the Precambrian platform, possibly during the initial generation of the Paleo Tethyan Seaand was succeeded by deposition of shallow marine limestone with abundant fossil trilobites and archeocyathids. The initial Paleo Pacific marginal seafloor was subducted—i.
A similar cycle of marginal sea generation and subsequent Mariana-type subduction within oceanic lithosphere accreted a second fold belt to eastern Australia during the Ordovician Period about to million years ago.
That was lange drifting away youtube by an interval of block faulting and widespread granitic intrusion in eastern Australia that produced a landscape similar to the present Basin and Range Province of the western United States ; by the late Devonian Period about million years ago the first of a series lange drifting away youtube magmatic orogenic arcs had become established by Chilean-type subduction of oceanic lithosphere beneath continental lithosphere on the eastern margin, and a thick succession of mainly sandstone and shale accumulated in the moatlike foreland basin between lange drifting away youtube mountain belt and the craton—the flat and relatively stable interior portion of the continent.