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Australia is a continent situated on the Indo-Australian Plate. The geology of Australia includes virtually all known rock types and from all geological time periods spanning over 3.8 billion years of the Earth's history. ==Components== Australia's geology can be divided into several main sections: the Archaean cratonic shields, Proterozoic fold belts and sedimentary basins, Phanerozoic sedimentary basins, and Phanerozoic metamorphic and igneous rocks. Australia as a separate continent began to form after the breakup of Gondwana in the Permian, with the separation of the continental landmass from the African continent and Indian subcontinent. Australia rifted from Antarctica in the Cretaceous. The current Australian continental mass is composed of a thick subcontinental lithosphere, over 200 km thick in the western two thirds and 100 km thick in the younger eastern third. The Australian continental crust, excluding the thinned margins, has an average thickness of 38 km, with a range in thickness from 24 km to 59 km. The continental crust is composed primarily of Archaean, Proterozoic and some Palaeozoic granites and gneisses. A thin veneer of mainly Phanerozoic sedimentary basins cover much of the Australian landmass (these are up to 7 km thick). These in turn are currently undergoing erosion by a combination of aeolian and fluvial processes, forming extensive sand dune systems, deep and prolonged development of laterite and saprolite profiles, and development of playa lakes, salt lakes and ephemeral drainage. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Geology of Australia」の詳細全文を読む スポンサード リンク
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