<P> The total length of the state's eastern border is 1,862 km (1,157 mi). There are 20,781 km (12,913 mi) of coastline, including 7,892 km (4,904 mi) of island coastline . The total land area occupied by the state is 2.5 million km . </P> <P> 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 Karoo 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 . </P> <P> 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). </P> <P> 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 . </P>

What is the elevation of most of western australia
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