Blue MountainsThis stunning vista was taken in the Blue Mountains National Park, New South Wales, Au

Blue MountainsThis stunning vista was taken in the Blue Mountains National Park, New South Wales, Australia.The image is dominated by an expansive valley and flat ‘peaks’ - not your traditional mountains.So, what about the geology? Well, the flat yellow cliffs in the background are sandstones, deposited around 200 million years ago. The rocks at the bottom of the valley are shales, siltstones and mudstones - marine sediments, deposited before the sandstone.How does such a beautiful and special landscape come into being? Rivers running at the bottom of the valleys hold the answer. They erode the rock, forging these impressive valleys and gorges. But the steep cliff faces and shallow valley floors are caused by the differences in the two lithologies. Sandstones are hard and resistant to erosion; but when the water gets to the softer muds, silts and shales it can erode them away easily. It then undercuts the sandstones above, which break off in large blocks, leaving vertical faces behind, and creating some fantastic views.SedgImage credit: SedgReferences and further reading: http://www.environment.nsw.gov.au/NationalParks/parkGeoFormation.aspx?id=N0004More detailed with pretty pictures:http://www.geomaps.com.au/scripts/bluemountainsoverview.phpMore recent history: http://www.bluemts.com.au/info/about/history/history-detail/ -- source link
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