Geology of Western Australia

The bulk of Western Australia consists of the extremely old Yilgarn craton and Pilbara craton which merged with the Deccan Plateau of India, Madagascar and the Kaapvaal and Zimbabwe cratons of Southern Africa, in the Archean Eon to form Ur, one of the oldest supercontinents on Earth (3 – 3.2 billion years ago). In May 2017, evidence of the earliest known life on land may have been found in 3.48-billion-year-old geyserite and other related mineral deposits (often found around hot springs and geysers) uncovered in the Pilbara 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 above 1,245 metres (4,085 ft) AHD (at Mount Meharry in the Hamersley Range of the Pilbara region). Most of the state is 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, nearly devoid of soluble phosphate and deficient in zinc, copper, molybdenum and sometimes potassium and calcium.

The infertility of most of the soils has required heavy application by farmers of fertilizers. These have resulted in damage to invertebrate and bacterial populations. The grazing and use of hoofed mammals and, later, heavy machinery through the years have resulted in compaction of soils and great damage to the fragile soils.

Large-scale land clearing for agriculture has damaged habitats for native flora and fauna. As a result, the South West region of the state 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.