Western Australia is Australia's largest state in area, covering the western third of the mainland, and is bordered by South Australia and the Northern Territory. It is, after the Sakha Republic in Russia, the second largest subnational entity in the world. Despite this the population is only 2,105,800 making up 10% of Australia's total population.
The people of Western Australia, West Australians or Western Australians, are often colloquially referred to as sandgropers because of the insect found on sand dunes around Perth.
The bulk of Western Australia consists of the extremely old Yilgarn craton and Pilbara craton which merged with the Deccan of India, Madagascar and the Karoo and Zimbabwe cratons of Southern Africa, in the Archean Eon to form Ur, one of the oldest Supercontinents on Earth (3,200-3,000 million years ago). 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 1,245 metres (4,085 ft) AHD (at Mount Meharry in the Hamersley Range of the Pilbara region). Most parts of the State form a low plateau with an average elevation of about 400 metres (1,200 ft), 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.
The infertility of most of the soils has required heavy inputs of chemical fertilisers, particularly superphosphate, insecticides and herbicides, which, with the ensuing damage to invertebrate and bacterial populations, and compaction of soils through heavy machinery and hoofed mammals has done great damage to the fragile soils. The massive clearing of the land has not only damaged habitats for native flora and fauna, making the South West region of the state that with the greatest percentage of flora and fauna rare, threatened or endangered in Australia, and one of the biodiversity "hot spots" in the world, it has also led to major problems with dryland salinity and the loss of fresh water.
The southwest coastal area is relatively temperate and was originally heavily forested, including large stands of the karri, one of the tallest trees in the world. This agricultural region of Western Australia is in the top nine terrestrial habitats for terrestrial biodiversity with a higher proportion of endemic species than most other equivalent regions, and thanks to the offshore Leeuwin Current, numbers in the top six regions for marine biodiversity, containing the most southerly coral reefs in the world. Annual rainfall varies from 300 millimetres (12 in) at the edge of the Wheatbelt region to 1,400 millimetres (55 inches) in the wettest areas near Northcliffe, but in the months of November to March evaporation exceeds rainfall and it is generally very dry. Plants must be adapted to this as well as the extreme poverty of all soils. A major reduction in rainfall has been observed, with a greater number of rainfall events in the summer months. This may be due to Climate change.
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 (8–10 in) but is very erratic because most of it is produced in torrential falls by cyclones in the summer months that are often unreliable.
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 1,500 millimetres (20–60 in), but there is a very long almost rainless season from April to November. Almost all (85%) 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.
Snow is only a regular occurrence on the Stirling Range near Albany, as it is the only mountain range far enough south and with sufficient elevation. More rarely, snow can fall on the Porongurup Range. Snow outside these areas is a major event; it usually occurs in hilly areas of southwestern Australia. The most widespread low-level snow occurred on 26 June 1956 when snow was reported in the Perth hills, as far north as Wongan Hills and as far east as Salmon Gums. However, even in the Stirling Range, snowfalls rarely exceed 5 cm (2 in) and rarely settle for more than one day.
Wording courtesy of http://www.wikipedia.org/