Geology of WA

The bulk of, WA, consists of the extremely old Yilgarn craton and Pilbara craton which merged with the Deccan Plateau of India, Madagascar and the Karoo and Zimbabwe cratons of Southern Africa, in the Archean Eon to form rUr, 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, WA, with the rifting from Antarctica , the land is extremely eroded and ancient, with no part of the state 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 ).WA.

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 sand plains 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 of WA.

Large-scale land clearing for agriculture and forestry has damaged habitats for native flora and fauna in WA. As a result, the South West region of the stateof WA, has a higher concentration of rare, threatened or endangered flora and fauna than many areas of Australia , making it one of the world's biodiversity "hot spots". Large areas of the state's wheatbelt region have problems with dryland salinity and the loss of fresh water.