page_title: Grampians National Park
section_title: Geology
hierarchical_section_title: Grampians National Park / Physiography / Geology
caption_attribution_description: A panoramic view of part of the Western end of the en:Grampians National Park, Australia. The large rock formation to the right is known as The Fortress. I don't know the name of the central formation.
context_page_description: The Grampians National Park commonly referred to as The Grampians, is a national park located in the Grampians region of Victoria, Australia. It lies within the region known as Gariwerd by Aboriginal Victorians of the area; Gariwerd extends across a wider area than the national park.
  The 167,219-hectare national park is situated between Stawell and Horsham on the Western Highway and Dunkeld on the Glenelg Highway, 260 kilometres west of Melbourne and 460 kilometres east of Adelaide. Proclaimed as a national park on 1 July 1984, the park was listed on the National Heritage List on 15 December 2006 for its outstanding natural beauty and being one of the richest Aboriginal rock art sites in south-eastern Australia.
  The Grampians feature a striking series of mountain ranges of sandstone. The Gariwerd area features about 90% of the rock art in the state.
context_section_description: The rock material that composes the high peaks is sandstone which was laid down from rivers during the Devonian period 425 - 415 million years ago. This sediment slowly accumulated to a depth of 7 kilometres (4.3 mi); this was later raised and tilted for its present form. 
  A number of stratigraphic layers have been identified, such as the Silverband Formation, the Mount Difficult Subgroup and the Red Man Bluff Subgroup. The coarse grain and fine lamination of the Silverstone Formation, along with undulations at the surface, is thought to have been an estuarine backwater before becoming preserved around 400 million years ago.
  The Southern Ocean reached the base of the northern and western base of the mountain range about 40 million years ago, the deposition from the range forming the sea floor which is now Little Desert National Park.
  The highest peak is Mount William at 1,167 metres (3,829 ft). Numerous waterfalls, such as Mackenzie Falls, are found in the park and are easily accessible via a well-developed road network.
caption: The western part of the park, with the rock formation known as The Fortress to the right
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