Western Australia

Western Australia is Australia's largest state, covering the western most third of the mainland, bordering South Australia and the Northern Territory. It is, after Sakha in Russia, the second largest subnational entity in the world.

Geography

Western Australia consists of several extremely old cratons which merged (probably during the Neoproterozoic) to form the Australian Craton. Because the only mountain-building since then has been of the Stirling Range with the rifting from Antarctica, the land is extremely eroded and ancient, with no part of the State today above 1245 metres (at Mount Meharry in the Pilbara). Most parts of the State form a low plateau with an average elevation of about 400 metres (1200 feet), very low relief, and no surface runoff. This descends relatively sharply to the coastal plains, in some cases forming a sharp escarpment (as with the Darling Range/Darling Scarp near Perth). The extreme age of the landscape has meant that the soils are remarkably infertile and frequently laterised. Even soils derived from granitic bedrock contain an order of magnitude less available phosphorus and only half as much nitrogen as soils in comparable climates in other continents. Soils derived from extensive sandplains or ironstone are even less fertile, being even more devoid of soluble phosphate and also deficient in zinc, copper, molybdenum and sometimes potassium and calcium.

Related Topics:
Craton - Neoproterozoic - Stirling Range - Plateau - Darling Scarp - Soil - Laterised - Granitic - Bedrock - Phosphorus - Nitrogen - Continent - Sand - Ironstone - Zinc - Copper - Molybdenum - Potassium - Calcium

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The state capital is the city of Perth, which lies on the south-western coastline. Perth's metropolitan area had an estimated population of 1.433 million in 2003 which was almost three quarters of the state's population. The Perth metropolitan area has grown to include the port of Fremantle and the town of Rockingham. Other important or well-known centres include Mandurah (pop. 54,000), Bunbury, Kalgoorlie, Albany, Geraldton, Port Hedland and Broome, but these are all relatively small cities or towns. The southwest coastal area is relatively temperate and forested. Annual rainfall varies from 300 millimetres (12 inches) at the edge of the wheatbelt to 1400 millimetres (55 inches) in the wettest areas near Northcliffe, but the months of November to March are generally very dry and plants must be adapted to this as well as the extreme poverty of all soils., The central four-fifths of the State is semi-arid or desert, and is lightly inhabited with the only significant activity being mining. Annual rainfall here averages about 200 to 250 millimetres (8 to 10 inches) but is very erratic because most of it is produced in torrential falls by cyclones that are often absent.

Related Topics:
State capital - Perth - Fremantle - Rockingham - Mandurah - Bunbury - Kalgoorlie - Albany - Geraldton - Port Hedland - Broome - Southwest coastal area - Semi-arid - Desert - Cyclones

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An exception to this is the northern tropical regions. The Kimberley has an extremely hot monsoonal climate with average annual rainfall ranging from 500 to 1500 millimetres (20 to 60 inches), but there is a very long almost rainless season from April to November. Almost all (85 percent) of the State's runoff occurs in the Kimberley, but because it occurs in violent floods and the insurmountable poverty of the generally shallow soils, the only development has taken place along the Ord River with an ambitious scheme that has only recently begun to pay off.

Related Topics:
Tropical - Kimberley - Monsoon - Runoff - Flood - Ord River

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