Wikipedia

Inselberg

(Redirected fromKopje)
"Monadnock" redirects here. For other uses, seeMonadnock (disambiguation).
For the type of water castle, seeInselburg.

Aninselbergormonadnock(/məˈnædnɒk/mə-NAD-nok) is an isolated rock hill, knob, ridge, or smallmountainthat rises abruptly from a gently sloping or virtually level surroundingplain. InSouthern Africa,a similar formation of granite[citation needed]is known as akoppie,anAfrikaansword ( "little head" ) from theDutchdiminutive wordkopje.[1]If the inselberg is dome-shaped and formed fromgraniteorgneiss,it can also be called abornhardt,though not all bornhardts are inselbergs. An inselberg results when a body of rock resistant to erosion, such as granite, occurring within a body of softer rocks, is exposed bydifferential erosionand lowering of the surrounding landscape.[2]

Pietra di Bismantovain theApennines,Italy

Etymology

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Inselberg

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The wordinselbergis aloan wordfromGerman,and means "island mountain". The term was coined in 1900 by geologistWilhelm Bornhardt(1864–1946) to describe the abundance of such features found in easternAfrica.[3]At that time, the term applied only to arid landscape features. However, it has since been used to describe a broader geography and range of rock features, leading to confusion about the precise definition of the term.

In a 1973 study examining the use of the term, one researcher found that the term had been used for features insavannahclimates 40% of the time, arid or semi-arid climates 32% of the time, humid-subtropical and arctic 12% of the time, and 6% each in humid-tropical and Mediterranean climates. A 1972 paper defined inselbergs as "steep-sided isolated hills rising relatively abruptly above gently sloping ground". This definition includes such features asbuttes;conical hills with rectilinear sides typically found in arid regions;regolith-covered concave-convex hills; rock crests over regolith slopes; rock domes with near vertical sides;tors(koppies) formed of large boulders but with solid rock cores. Thus, the terms monadnock and inselberg may not perfectly match,[4]though some authors have explicitly argued these terms are completely synonymous.[5]

Monadnock

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Monadnockis derived from anAbenakiterm for an isolatedhillor a lone mountain that stands above the surrounding area, typically by surviving erosion. Geologists took the name fromMount Monadnockin southwesternNew Hampshire.[6]It is thought to derive from eithermenonadenak(transl. smooth mountain) ormenadena(transl. isolated mountain).[7]In this context,monadnockis used to describe a mountain that rises from an area of relatively flat and/or lower terrain. For instance, Mount Monadnock rises 610 metres (2,000 ft) above its surrounding terrain and stands, at 965 m (3,165 ft), nearly 300 m (1,000 ft) higher than any mountain peak within 48 km (30 mi).[8]

Geology

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Geological and geographical patterns

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TheSpitzkoppeof Namibia, a 670-metre (2,200 ft)granitepeak formed by earlyCretaceousrifting and magmatism.

Inselbergs are common in eroded and weatheredshields.[9]The presence of an inselberg typically indicates the existence of a nearbyplateauor highland, or their remnants. This is especially the case for inselbergs composed ofsedimentary rock,which will display the same stratigraphic units as this nearby plateau. However once exposed, the inselbergs are destroyed by marginal collapse ofjoint blocks and exfoliation sheets.This process leaves behindtorsperched at their summits and, over time, atalus-bordered residual known as acastle koppieappears.[10][11]By this association various inselberg fields in Africa and South America are assumed to be the vestiges of erodedetchplains.[12][13]

Clusters of inselbergs, called inselberg fields and inselberg plains, occur in various parts of the world, includingTanzania,[14]theAnti-AtlasofMorocco,[12]Northeast Brazil,[15]Namibia,[16]the interior ofAngola,[17]and the northern portions ofFinland[18][19]andSweden.[20][A]

The classification of Anthony Young (1969) distinguishes six types of inselbergs;buttes,conical hills,convex-concave hills, rock crest over regolith-covered slope,rock dome(sugarloaf) andkopje or tor.[22]

The types of rock of which inselbergs are made includegranite,gneissandgabbro.[B]

Origin and development

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Summarizing the understanding on the origin of inselbergs in 1974, geomorphologist Michael Thomas writes "Hypotheses for the development of inselbergs have been advanced, refuted and reiterated over a period of more than seventy years."[24]Volcanicor other processes, such as ameteor crater,may give rise to a body ofrockresistant toerosion,inside a body of softer rock such aslimestone,which is more susceptible to erosion. When the less resistant rock is eroded away to form aplain,the more resistant rock is left behind as an isolated mountain. The strength of the uneroded rock is often attributed to the tightness of itsjointing.[25][C]

Inselbergs can be reshaped byice sheetsmuch the same way asroches moutonnées.Innorthern Sweden,examples of this type of inselberg are calledflyggbergs.[27]: 326–327 [28]

Ecology

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Lion atop a koppie in theSerengeti,northernTanzania

The inselbergs of Eastern Africa tend to be a refuge for life in theSerengetiofTanzaniaand in theMasai MaraofKenya.Where the soil is too thin or hard to support tree life in large areas, soil trapped by inselbergs can be dense with trees while the surrounding land contains only short grass. Hollows in the rock surfaces provide catchments for rainwater. Many animals have adapted to the use of inselbergs, including thelion,thehyrax,and an abundance of bird and reptile life.

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See also

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  • Bornhardt– A large dome-shaped, steep-sided, bald rock
  • Caprock– Rock overlying a less resistant type
  • Dissected plateau– Plateaus area that has been severely eroded so that the relief is sharp
  • List of inselbergs
  • Mesa– Elevated area of land with a flat top and sides, usually much wider than buttes
  • Mogote– Steep-sided residual hill of limestone, marble, or dolomite on a flat plain
  • Sky island– Geographic or environmental feature
  • Table (landform)– Raised landform with a flat top
  • Tuya– Flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet

Notes

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  1. ^Albeit its not the usual way of describing it thestrandflatof Norway was held byJulius Büdelto be anetchplainwith inselbergs.[21]
  2. ^Cliff Ollierhas noted that inUgandainselbergs are commonly made of granite rock, sometimes ofgneissand never ofamphiboliteorvolcanic rock.[2]According to Ollier protuding quartzite hills tend to form ridges rather than "true inselbergs".[2]Dundretin northern Sweden is made ofgabbro.[23]
  3. ^Twidale (1981)"Granitic Inselbergs:…"[26]is a review that follows the Willis 1936 works and Twidale 1971, a series of papers available in 1970 and rock weathering strata and structure reviewed U.C.W. well worth reading as they show by theory and materials the importance of preceding structures, internal solution, subsurface weathering, slips, exfoliation, basal weathering (Young, A.Soils), biological effects, plants, solutes and salt plain catena associations, possible lake rise, but mainly the stripping of rock mass leaving resistant units, sometimes volcanic plugs.

References

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  1. ^Webster's New Explorer Dictionary of Word Origins(2004). Federal Street Press: New York.
  2. ^abcOllier, C.D.(1960). "The Inselbergs of Uganda".Zeitschrift für Geomorphologie.4(1): 43–52.
  3. ^Holmes, Arthur (1978).Holmes Principles of Physical Geology.Nelson.ISBN978-0-17-771299-9.[page needed]
  4. ^Gerrard, John (1988).Rocks and LandformsRoutledge: Florence, Kentucky.
  5. ^King, Lester C.(1953). "Canons of landscape evolution".Geological Society of America Bulletin.64(7): 721.doi:10.1130/0016-7606(1953)64[721:COLE]2.0.CO;2.
  6. ^Raymo, ChetandRaymo, Maureen E.(1989)Written in Stone: A Geologic History of the Northeastern United States.Globe Pequot, Chester, Connecticut.
  7. ^"Vermont Soils with Names of American Indian OriginArchived2009-03-20 at theWayback Machine"United States Department of Agriculture, Natural Resources Conservation Service. Retrieved January 6, 2008.
  8. ^Baldwin, Henry I. (1989).Monadnock Guide 4th edition.Concord, New Hampshire:Society for the Protection of New Hampshire Forests.
  9. ^Nenonen, Keijo; Johansson, Peter; Sallasmaa, Olli; Sarala, Pertti; Palmu, Jukka-Pekka (2018)."The inselberg landscape in Finnish Lapland: a morphological study based on the LiDAR data interpretation".Bulletin of the Geological Society of Finland.90(2): 239–256.doi:10.17741/bgsf/90.2.008.
  10. ^"Summary: Inselbergs/Hills/Knobs".Desert Processes Working Group. Knowledge Sciences, Inc.Retrieved6 January2008.
  11. ^Easterbrook, Don J. (1999). "Chapter Three: Weathering".Surface Processes and Landforms(2nd ed.). Upper Saddle River, NJ: Prentice Hall.
  12. ^abGuillocheau, François; Simon, Brendan; Baby, Guillaume; Bessin, Paul; Robin, Cécile; Dauteuil, Olivier (2017)."Planation surfaces as a record of mantle dynamics: The case example of Africa"(PDF).Gondwana Research.53:82.Bibcode:2018GondR..53...82G.doi:10.1016/j.gr.2017.05.015.
  13. ^García, Carolina; Hermelin, Michel (2016). "Inselbergs Near Medellín". In Hermelin, Michel (ed.).Landscapes and Landforms of Colombia.Springer. p. 219.ISBN978-3-319-11800-0.
  14. ^Sundborg, Å.;Rapp, A.(1986).Erosion and Sedimentation by Water: Problems and prospects.Ambio.pp. 215–225.
  15. ^Maia, Rúbson Pinheiro; Frêgo Bezerra, Francisco Hilário; Leite Nascimento, Marcos Antônio; Sampaio de Castro, Henrique; de Andrade Meireles, Antônio Jeovah; Rothis, Luis Martin (2015)."Geomorfologia do Campo de Inselbergues de Quixadá, nordeste do Brasil"[Geomorphology of inselbergs field of Quixadá, Northeast Brazil].Revista Brasileira de Geomorfologia(in Portuguese).16(2).doi:10.20502/rbg.v16i2.651.hdl:11336/6639.
  16. ^"Production of an agro-ecological zones map of Namibia (first approximation)"(PDF).nbri.org.na.
  17. ^"Development of a soil and terrain map/database for Angola"(PDF).Archived fromthe original(PDF)on 2021-03-09.Retrieved2016-07-11.
  18. ^Kaitanen, Veijo (1 February 1985)."Problems concerning the origin of inselbergs in Finnish Lapland".Fennia.163(2): 359–364.
  19. ^Ebert, K.; Hall, A.; Hättestrand, C.; Alm, G. (2009). "Multi-phase development of a glaciated inselberg landscape".Geomorphology.115(1): 56–66.doi:10.1016/j.geomorph.2009.09.030.
  20. ^Rudberg, S.(1988). "Gross morphology of Fennoskandia: Six complementary ways of explanation".Geografiska Annaler.A. Physical Geography.70(3): 135–167.doi:10.2307/521068.JSTOR521068.
  21. ^Olesen, Odleiv; Kierulf, Halfdan Pascal; Brönner, Marco; Dalsegg, Einar; Fredin, Ola; Solbakk, Terje (2013)."Deep weathering, neotectonics and strandflat formation in Nordland, northern Norway"(PDF).Norwegian Journal of Geology.93:189–213.S2CID226225485.
  22. ^Young, Anthony (1969). Clayton, K.M. (ed.).Slopes.Edinburgh: Oliver & Boyd. p. 209.
  23. ^Ebert, Karin; Hall, Adrian M.; Hättestrand, Clas (2012). "Pre-glacial landforms on a glaciated shield: The inselberg plains of northern Sweden".Norwegian Journal of Geology.92:1–17.
  24. ^Thomas, Michael (1974).Tropical Geomorphology.The Macmillan Press Ltd. p. 136.
  25. ^"A Dictionary of Ecology" (2004). Encyclopedia. Retrieved November 28, 2009
  26. ^Twidale, C.R.(1981). "Granitic Inselbergs: Domed, Block-Strewn and Castellated".The Geographical Journal.147(1): 54–71.doi:10.2307/633409.JSTOR633409.
  27. ^Benn, Douglas; Evans, David (1998).Glaciers & Glaciation(1st ed.). London, UK: Arnold.ISBN978-0-340-58431-6.
  28. ^Lidmar-Bergström, Karna;Olvmo, Mats (2015).Plains, Steps, Hilly Relief and Valleys in Northern Sweden--review, Interpretations and Implications for Conclusions on Phanerozoic Tectonics(PDF).Sveriges geologiska undersökning (Geological Survey of Sweden). p. 13.ISBN978-91-7403-308-3.OCLC943395499.Retrieved29 June2016.
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