page_title: Greater Western Sydney
section_title: Geology
hierarchical_section_title: Greater Western Sydney / Geography / Geology
caption_attribution_description: Nepean River at Penrith New South Wales. This section is called "The Narrows". Beyond here the river enters the Nepean Gorge.
context_page_description: Greater Western Sydney is a large region of the metropolitan area of Greater Sydney, New South Wales, Australia that generally embraces the north-west, south-west, central-west, and far western sub-regions within Sydney's metropolitan area and encompasses 13 local government areas: Blacktown, Canterbury-Bankstown, Camden, Campbelltown, Cumberland, Fairfield, Hawkesbury, Hills Shire, Liverpool, Parramatta, Penrith, Wollondilly and the western portion of the City of Parramatta Council. It includes Western Sydney, which has a number of different definitions, although the one consistently used is the region composed of the nine local government authorities which are all members of the Western Sydney Regional Organisation of Councils. The NSW Government's Office of Western Sydney uses the broader Greater Western Sydney definition to refer to the region.
  Radiocarbon dating suggests human activity occurred in the Sydney metropolitan area from around 30,000 years ago. The Darug people lived in the area that was greater western Sydney before European settlement regarded the region as rich in food from the river and forests.
context_section_description: The Sydney area lies on Triassic shales and sandstones with low rolling hills and wide valleys in a rain shadow area. Sydney sprawls over two major regions: the Cumberland Plain, a relatively flat region lying to the west of Sydney Harbour, and the Hornsby Plateau, a plateau north of the Harbour rising to 200 metres and dissected by steep valleys. Sydney's native plant species are predominantly eucalyptus trees, and its soils are usually red and yellow in texture.
  At a time in the past, monocline formed to the west of Sydney. The monocline is a sloping bend that raises the sandstone well above where it is expected to be seen, and this is why the whole of the visible top of the Blue Mountains is made of sandstone. Sandstone slopes in the Sydney area are on three sides: to the west the Blue Mountains, and to the north and south, the Hornsby and Woronora plateaux'. The centre of the Sydney basin is located beneath Fairfield. Bringelly Shale and Minchinbury Sandstone are often seen in the greater western parts of Sydney, which are part of the Wianamatta Shale group. Prospect Hill in western Sydney is the largest assemblage of igneous rock in Sydney. The oval-shaped ridge was made many millions of years ago when volcanic material from the Earth's upper mantle moved upwards and then sideways.
  Swamps and lagoons are existent on the floodplain of the Nepean River, one being Bents Basin, which is also a recreational area. Parramatta River drains a large area of Sydney's western suburbs. With 5,005,400 inhabitants (as of 2016) and an urban population density of 2037 people per square kilometre, Sydney's urban area covers 1,788 square kilometres (690 sq mi), comprising 35% of Sydney and is constantly growing. The south and southwest of Sydney is drained by the Georges River, flowing north from its source near Appin, towards Liverpool and then turning east towards Botany Bay. Minor waterways draining Sydney's western suburbs include South Creek and Eastern Creek, flowing into the Hawkesbury, and Prospect Creek draining into the Georges River. Cowan Creek and Berowra Creek run north from the Upper North Shore to the Hawkesbury river.
caption: Most of Sydney's water storages are on tributaries of the Nepean River.
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