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Norber erratics
The Norber erratics are one of the finest groups of glacial erratic boulders in Britain. They are found on the southern slopes of Ingleborough, close to the village of Austwick in the Yorkshire Dales. The Ordnance Survey grid reference of the boulder field is SD764698.
The Norber erratics are classic geomorphological features from the glaciation of northern England. In his chapter on the Pennines, Trueman (1949, p.169) wrote: "Particularly well known are the great perched blocks of dark grit which stand on the limestone platform at Norber near Settle."〔A.E. Trueman (1949) Geology and Scenery in England and Wales. Pelican, 334pp.〕
Many of the Millstone Grit boulders at the site are perched on pedestals of limestone up to 30cm high. The boulders were probably deposited by melting ice sheets at the end of the last ice age, around 12,000 years ago. The pedestals have developed because the erratic boulders have protected the underlying limestone from solution by rainfall, giving estimates of the rate of lowering of the surrounding limestone pavement of around 25mm per 1000 years.〔A. Goudie and R. Gardner (1992) Discovering Landscape in England and Wales. Chapman and Hall, 177pp.〕 Recent cosmogenic dating suggests that the boulders have been exposed for around 17,900 years.〔S. Drury (2013) Update on a classic British field site. http://earth-pages.co.uk/tag/glacial-erratic/ Site accessed 8th January 2015.〕
==References==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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