page_title: Geology of South Australia
section_title: Description
hierarchical_section_title: Geology of South Australia / Lake Eyre Basin / Description
caption_attribution_description: This is a map of the Lake Eyre drainage basin including the major rivers. Note that the river courses shown are usually dry.
context_page_description: South Australia is an Australian state, situated in the southern central part of the country, and featuring some low-lying mountain ranges, the most significant being the Mount Lofty Ranges, which extend into the state's capital city, Adelaide, which comprises most of the state's population. Adelaide is situated on the eastern shores of Gulf St Vincent, on the Adelaide Plains, north of the Fleurieu Peninsula, between Gulf St Vincent and the low-lying Mount Lofty Ranges. The state of South Australia, which stretches along the coast of the continent and has boundaries with every other state in Australia, with the exception of the Australian Capital Territory and Tasmania. The Western Australia border has a history with South Australia, involving the South Australian Government Astronomer, Dodwell and the Western Australian Government Astronomer, Curlewis in the 1920s to mark the border on the ground.
  The search for underground water and mineral wealth was the principal stimulus to the growth of geology of South Australia.
context_section_description: The Lake Eyre Basin is the largest endorheic basin in Australia and is over 1.14 million square kilometres. The basin lies in the north east of the state of South Australia. Its South Australian territory is predominantly semi-arid to arid land. As an endorheic basin, it has no outflows to other bodies of water such as oceans or rivers. As a result, the main causes of water loss are evaporation and seepage. The Lake Eyre Basin consists of seven drainage catchments, with the Georgina Diamantina, Cooper Creek and Neales Peake catchments located fully or partially in South Australia.
  Rainfall is one of the most influential climatic processes that acts upon the Lake Eyre Basin. The Lake Eyre Basin receives more rainfall during the summer season due to the high-pressure ridge of the Handley Cell. Likewise, the basin receives less rainfall during winter. Statistics from the Australian Bureau of Meteorology show that rainfall in winter totalled 8mm whilst in summer it was 38mm. This is more profound in Lake Eyre and the basin’s South Australian territories, with an average annual rainfall of roughly 125mm, yet its average evaporation can reach over 3600mm. Consequently, this is the cause of the semi-arid and arid terrain found throughout South Australian Lake Eyre territories.
  The Lake Eyre Basin consists predominantly of Mesozoic and Cenozoic rocks, which refers to the date of the rocks’ formation, from 248 million years ago to the present day. Additionally, there is also a presence of tertiary and quaternary sediments in surface layers of the Lake Eyre Basin. The basin was formed due to land subsidence over 200 million years ago. Sea-level fluctuations caused the basin to be inundated over 100 years ago, with the ocean receding from the basin 25 million years ago. Lake Eyre Basin gained its endorheic status roughly one million years ago as the salt lakes within its area began blocking water outflows to rivers.
caption: A map of the Lake Eyre Basin
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