After the ice melted, parts of the continent subsided and formed sedimentary basins such as the Eromanga Basin in South Australia. Australia began its journey across the surface of the Earth as an isolated continent between about 55 and 10 million years ago, and continues to move north by about seven centimetres each year.Īustralia's present topography is the result of a long landscape history, which, fundamentally, started in the Permian Period when Australia was very near the South Pole, and much of the continent was glaciated by large ice caps. The Finke River in central Australia is one of the oldest rivers in the world and salt lakes of the Yilgarn region in Western Australia are the remnants of a drainage pattern which was active before continental drift separated Australia from Antarctica. Many of the features of the drainage pattern have a very long history, and some individual valleys have maintained their position for millions of years.
About 50 per cent of Australia's rivers drain inland and often end in ephemeral salt lakes. Īlthough the shape of Australia is due largely to tectonic Earth movements and long term changes in sea level, most of its topography is a result of prolonged erosion by wind and water. Recently, scientists have been able to obtain a much clearer picture of Australia's geological past through deep seismic surveys, which has provided new information about how the continent was formed, particularly around Broken Hill, Mount Isa, Iron Knob and West Arnhem Land.
The continent is home to rocks dating from more than 3000 million years while others are the result of volcanic activity which continued up to only a few thousand years ago. Australia is a land of geological contradictions with some of the oldest features in the world alongside rocks which are in the process of formation.
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