Bornhardt

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A bornhardt (/ˈbɔrnˈhɑrt/) is a dome-shaped, steep-sided, bald rock outcropping at least 30 metres (100 ft) in height and several hundred metres in width.[1] A type of inselberg, bornhardts are typically composed of granites or gneisses, though occasionally formed in other rock types such as dacite, norite, limestone, sandstone and conglomerate. Uluru, in Central Australia, is mainly composed of sandstones, while the nearby Kata Tjuta is composed of conglomerates. They are named after Wilhelm Bornhardt (1864–1946), a German geologist and explorer of German East Africa, who first described the feature.[2][3] The Sugar Loaf Mountain of Rio de Janeiro is a typical example of this landform and is the origin of the common bornhardt nickname "sugar loaf".[4]

Bornhardts are seen at their best in arid and semi-arid regions, but occur over a wide range of climates. Found in diverse topographic settings they mainly occur in multicyclic landscapes. They give rise to other types of inselberg, such as nubbins (or knolls) and castle koppies.[5]

Depending on their shape they are known as sugar loaves, whalebacks, turtlebacks or simply domes. They are locally known as dwalas, half-oranges, matopos, etc. Often, the underlying geological fracture pattern is shown by the surface arrangement of bornhardts, as can be seen in the Kamiesberge of Namaqualand and the Everard Ranges of Central Australia.[6]

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References[edit]

  1. ^ Mayhew, Susan (2004). A Dictionary of Geography (3rd ed.). Oxford University Press. ISBN 0-19-860673-7. 
  2. ^ "Glossery of Terms: Bornhardt". Yonsei.ac.kr. InfoCenter for Environmental Geology. Archived from the original on 26 October 2011. 
  3. ^ Twidale, C R; Romaní, J R V (2005). "Inselbergs and Bornhardts". Landforms and Geology of Granite Terrains. New York: A.A. Balkema. pp. 109–116. ISBN 0-415-36435-3. 
  4. ^ Allaby, Michael (2004). A Dictionary of Ecology (2nd ed.). Oxford University Press. ISBN 0-19-860944-2. 
  5. ^ Twidale, C R (2007). "Bornhardts and associated fracture patterns". Revista de la Asociación Geológica Argentina 62 (1): 139–153. ISSN 0004-4822. hdl:2440/43513. 
  6. ^ Twidale, C R (1981). "Granitic Inselbergs: Domed, Block-Strewn and Castellated". The Geographical Journal 147 (1): 54–71. JSTOR 633409. 

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