Australia - Topography And Origin Of Australia, Splitting Of Australia From Antarctica, Seismic Activity And Faulting, Overall Geological Structure - South Australian mountains, Glaciers and ocean inundations, Geology of Tasmania, Climate
island million continent marine
Of the seven continents, Australia is the flattest, smallest, and except for Antarctica, the most arid. Including the southeastern island of Tasmania, the island continent is roughly equal in area to the United States, excluding Alaska and Hawaii. Millions of years of geographic isolation from other landmasses accounts for Australia's unique animal species, notably marsupial mammals like the kangaroo, egg laying mammals like the platypus, and the flightless emu bird. Excluding folded structures (areas warped by geologic forces) along Australia's east coast, patches of the northern coastline and the relatively lush island of Tasmania, the continent is mostly dry, bleak, and inhospitable.
Other major mountain ranges rise in the eastern section of South Australia near Adelaide: the Flinders and Mount Lofty Ranges. These mountains arose from the Adelaidian Geosyncline (another large trough upon which sediments have been deposited) and were first uplifted over 500 million years ago during the Cambrian and Ordovician eras. Further thrusting occurred more recently, about 200 million years ago during the Mesozoic era.
In parts of Western Australia, particularly the Carnarvon Basin at the mouth of the Gascoyne River, glacial sediments are as thick as three miles. Western Australia, particularly along the coast, has been inundated repeatedly by the sea and has been described by geologists as a mobile shelf area. This is reflected in the alternating strata of deposited marine and non-marine layers.
During the early to mid-Jurassic period, there was an intrusion of 2,000 cubic miles of dark, layered volcanic rocks in Tasmania, similar to the magmatic formations
Ayers Rock, central Australia, 1,143 ft (349 m) high. JLM Visuals. Reproduced by permission.
of the Karroo region in South Africa and the Palisades in New York. Tasmania separated from mainland Australia only 10,000 years ago, when sea levels rose after the thawing of the last ice age.
The climatological record of Australia shows a pronounced temperature drop on the continent in the late Miocene and early Pliocene epochs between 26 and five million years ago when monkeys and early apes first evolved and saber toothed cats prowled the earth. On the Eyre Peninsula in South Australia and in Gippsland in Victoria, eucalyptus and acacia trees supplanted the previously dominant beech trees that had thrived in the warmer climate of the Miocene era.
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Australia has been less affected by seismic and orogenic (mountain building) forces than other continents during the past 400 million years. Although seismic (earthquake) activity persists in the eastern and western highlands, Australia is the most stable of all continents. In the recent geological past, it has experienced none of the massive upheavals responsible for uplifting the Andes in South …
About 95 million years ago, tectonic forces (movements and pressures of the earth's crust) split Australia from Antarctica and the southern supercontinent of Gondwanaland. Geologists estimate that the continent is drifting northward at a rate of approximately 18 inches (28 cm) per year. They theorize that south Australia was joined to Antarctica at the Antarctic regions of Wilkes Land, incl…
Furthermore, Australia and Antarctica are dissimilar to other land masses; their shapes are not rough triangles with apexes pointing southward like South America, Africa, and the Indian subcontinent, Gondwanaland's other constituent parts. However, like its sister continents, Australia is composed of three structural units. These include in Western Australia a stable and ancient block of ba…
Twice, during a 125 million year period beginning 400 million years ago, the geosynclines were compressed, forming mountains and initiating volcanos. Volcanic activity recurred along the Great Dividing Range 20-25 million years ago during the Miocene epoch when early apes evolved as well as seals, dolphins, sunflowers, and bears. However, over millions of years the volcanic cones from this epoch h…
In 1991, geologists discovered a subterranean electrical current in Australia, the longest in the world, which passes through more than 3,700 mi (6,000 km) across the Australian outback. The current is conducted by sedimentary rocks in a long horseshoe arc that skirts a huge mass of older igneous and metamorphic rock comprising most of the Northern Territory. It begins at Broome in Western Austral…
The continent's oldest rocks are in the Western Australian shield in southwest Australia. The basement (underlying) rocks in this area have not been folded since the Archean eon over three billion years ago, when the planet was still very young. The nucleus of this shield (called the Yilgarn craton) comprising 230,000 sq mi (59,570,000 ha), consists mostly of granite with belts of metamorph…
Geologists determine the age of rock strata by examining the fossils they contain. Geologists and paleontologists examine strata and establish the age of their surrounding sediments based on the types of fossilized specimens they find. For example, tribolites, tiny animals with shells, flourished in the Cambrian period. So when geologists find sediments chock full of tribolite fossils they know th…
Victoria is also characterized by a belt of old rocks upon which sediments have been deposited called the Lachlan geosyncline. Marine rocks were deposited in quiet water to great thicknesses in Victoria, forming black shales. Some of the sediment was built up by mud-laden currents from higher areas on the sea floor. These current-borne sediments have produced muddy sandstones called graywackes. At…
In the center of Australi a is a large sedimentary basin or depression spanning 450 mi (720 km) from east to west and 160 mi (256 km) north to south at its widest point. Sedimentary rocks of all varieties can be found in the basin rocks which erosion shaped into spectacular scenery including Ayres Rock and Mt. Olga. These deposits are mostly of pre-Cambrian age (over 570 million years old), while …
Of course geology is inextricably intertwined with natural resources and mineral exploitation. Minerals in Australia have had a tremendous impact on the country's human history and patterns of settlement. Alluvial gold (gold sediments deposited by rivers and streams) spurred several gold fevers and set the stage for Australia's present demographic patterns. During the post-World War …
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Katie Hunston
Who wrote this and when?