Inselberg

{{Short description|Isolated, steep rock hill on relatively flat terrain}} {{Redirect|Monadnock}} {{For|the type of water castle|Island castle{{!}}Inselburg}} [[File:ULURU.jpg|thumb|upright=1.2|Uluru in Australia]]

An '''inselberg''' or '''monadnock''' ({{IPAc-en|m|ə|ˈ|n|æ|d|n|ɒ|k}} {{respell|mə|NAD|nok}}) is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain.{{efn-ua|In Southern Africa, a similar formation of granite{{citation needed|reason=that it must be granite|date=September 2023}} is known as a '''koppie''', an Afrikaans word ("little head") from the Dutch diminutive word ''kopje''.<ref>''Webster's New Explorer Dictionary of Word Origins'' (2004). Federal Street Press: New York.</ref>}} If the inselberg is dome-shaped and formed from granite or gneiss, it can also be called a ''bornhardt'', 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 by differential erosion and lowering of the surrounding landscape.<ref name=Zeit1960/>

== Etymology == [[File:Pietra di bismantova castelnovo monti.jpg|thumb|right|Pietra di Bismantova in the Apennines, Italy]] === Inselberg === The word ''inselberg'' is a loan word from German, and means "island mountain". The term was coined in 1900 by geologist Wilhelm Bornhardt (1864–1946) to describe the abundance of such features found in eastern Africa.<ref>{{cite book |last1=Holmes |first1=Arthur |title=Holmes Principles of Physical Geology |date=1978 |publisher=Nelson |isbn=978-0-17-771299-9 }}{{page needed|date=December 2021}}</ref> 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 in savannah climates 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.

=== Monadnock === [[File:Mount Monadnock.JPG|thumb|Mount Monadnock in New Hampshire, USA.]] ''Monadnock'' is derived from an Abenaki term for an isolated hill or a lone mountain that stands above the surrounding area, typically by surviving erosion. Geologists took the name from Mount Monadnock in southwestern New Hampshire.<ref name="Raymo">Raymo, Chet and Raymo, Maureen E. (1989) ''Written in Stone: A Geologic History of the Northeastern United States.'' Globe Pequot, Chester, Connecticut.</ref> It is thought to derive from either {{lang|abe|menonadenak}} ({{Translation|smooth mountain}}) or {{lang|abe|menadena}} ({{Translation|isolated mountain}}).<ref>"[https://www.nrcs.usda.gov/state-offices/vermont Vermont Soils with Names of American Indian Origin] " United States Department of Agriculture, Natural Resources Conservation Service. Retrieved January 6, 2008.</ref> In this context, ''monadnock'' is used to describe a mountain that rises from an area of relatively flat and/or lower terrain. For instance, Mount Monadnock rises {{convert|2000|ft|m|order=flip}} above its surrounding terrain and stands, at {{convert|3165|ft|m|order=flip|abbr=on}}, nearly {{convert|1000|ft|m|order=flip|abbr=on}} higher than any mountain peak within {{convert|30|mi|km|order=flip|abbr=on}}.<ref>Baldwin, Henry I. (1989). ''Monadnock Guide 4th edition.'' Concord, New Hampshire: Society for the Protection of New Hampshire Forests.</ref>

==Definition== [[File:Cono de Arita (Argentina).jpg|thumb|Cono de Arita, a conical sandstone inselberg in the middle of Salar de Arizaro, Argentina]] 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) and kopje or tor.<ref name=Young1969>{{Cite book|title=Slopes|last=Young|first=Anthony|publisher=Oliver & Boyd|year=1969|location=Edinburgh|pages=209|editor-last=Clayton|editor-first=K.M.}}</ref>

A 1972 paper defined inselbergs as "steep-sided isolated hills rising relatively abruptly above gently sloping ground". This definition includes such features as buttes; 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,<ref name="gerrard">Gerrard, John (1988). ''[https://archive.org/details/rockslandforms0000gerr/page/209  Rocks and Landforms]'' Routledge: Florence, Kentucky.</ref> though some authors have explicitly argued these terms are completely synonymous.<ref name="King53">{{cite journal |last1=King |first1=Lester C. |authorlink1=Lester Charles King |title=Canons of landscape evolution |journal=Geological Society of America Bulletin |date=1953 |volume=64 |issue=7 |pages=721 |doi=10.1130/0016-7606(1953)64[721:COLE]2.0.CO;2 }}</ref>

== Geology == ===Geological and geographical patterns === [[File:2008-06-28 08-18-02 Namibia Erongo Usakos.JPG|thumb|The Spitzkoppe of Namibia, a {{Convert|670|m|ft|abbr=|adj=on}} granite peak formed by early Cretaceous rifting and magmatism.]] Inselbergs are common in eroded and weathered shields.<ref name=Nenonenetal2018>{{cite journal |last1=Nenonen |first1=Keijo |last2=Johansson |first2=Peter |last3=Sallasmaa |first3=Olli|last4=Sarala |first4=Pertti |last5=Palmu |first5=Jukka-Pekka |date=2018 |title=The inselberg landscape in Finnish Lapland: a morphological study based on the LiDAR data interpretation |journal=Bulletin of the Geological Society of Finland |volume=90 |issue=2 |pages=239–256 |doi=10.17741/bgsf/90.2.008|bibcode=2018BuGSF..90..239N |doi-access=free }}</ref> The presence of an inselberg typically indicates the existence of a nearby plateau or highland, or their remnants. This is especially the case for inselbergs composed of sedimentary rock, which will display the same stratigraphic units as this nearby plateau. Once exposed, the inselbergs are destroyed by marginal collapse of joint blocks and exfoliation sheets. This process leaves behind tors perched at their summits and, over time, a talus-bordered residual known as a ''castle koppie'' appears.<ref>{{cite web |url=http://www.tec.army.mil/research/products/desert_guide/lsmsheet/lsinsel.htm |archive-url=https://web.archive.org/web/20070713213412/http://www.tec.army.mil/research/products/desert_guide/lsmsheet/lsinsel.htm |url-status=dead |archive-date=2007-07-13 |title=Summary: Inselbergs/Hills/Knobs |department=Desert Processes Working Group |publisher=Knowledge Sciences, Inc. |access-date=January 6, 2008 |df=dmy-all}}</ref><ref>{{cite book |last=Easterbrook |first=Don J. |chapter=Chapter Three: Weathering |title=Surface Processes and Landforms |edition=2nd |location=Upper Saddle River, NJ |publisher=Prentice Hall |year=1999 }}</ref> By this association various inselberg fields in Africa and South America are assumed to be the vestiges of eroded etchplains.<ref name=Guillocheauetal2017/><ref name=GarciaHermelin>{{cite book |last1=García |first1=Carolina |last2=Hermelin |first2=Michel |date=2016 |chapter=Inselbergs Near Medellín |title=Landscapes and Landforms of Colombia |editor-last=Hermelin|editor-first=Michel |publisher=Springer |page=219 |isbn=978-3-319-11800-0}}</ref>

===Location=== thumb|A conical sandstone koppie in the Free State, South Africa Clusters of inselbergs, called inselberg fields and inselberg plains, occur in various parts of the world, including Tanzania,<ref>{{cite book |author1=Sundborg, Å. |author1-link=Åke Sundborg |author2-link=Anders Rapp |author2=Rapp, A. |year=1986 |title=Erosion and Sedimentation by Water: Problems and prospects |publisher=Ambio |pages=215–225}}</ref> the Anti-Atlas of Morocco,<ref name=Guillocheauetal2017>{{cite journal |last1=Guillocheau |first1=François |last2=Simon |first2=Brendan|last3=Baby |first3=Guillaume|last4=Bessin |first4=Paul|last5=Robin |first5=Cécile|last6=Dauteuil |first6=Olivier |date=2017 |title=Planation surfaces as a record of mantle dynamics: The case example of Africa |journal=Gondwana Research|volume=53 |page=82 |doi=10.1016/j.gr.2017.05.015 |bibcode=2018GondR..53...82G |url=https://hal-insu.archives-ouvertes.fr/insu-01534695/file/guillocheau-GondRes-2017.pdf }}</ref> Northeast Brazil,<ref>{{cite journal |last1=Maia |first1=Rúbson Pinheiro |last2=Frêgo Bezerra |first2=Francisco Hilário |last3=Leite Nascimento |first3=Marcos Antônio |last4=Sampaio de Castro |first4=Henrique |author-last5=de Andrade Meireles |author-first5=Antônio Jeovah |author-last6=Rothis |author-first6=Luis Martin |date=2015 |title=Geomorfologia do Campo de Inselbergues de Quixadá, nordeste do Brasil |trans-title=Geomorphology of inselbergs field of Quixadá, Northeast Brazil |journal= Revista Brasileira de Geomorfologia|volume=16 |issue=2 |page=651 |doi=10.20502/rbg.v16i2.651 |bibcode=2015RvBrG..16..651M |language=Portuguese|doi-access=free |hdl=11336/6639 |hdl-access=free }}</ref> Namibia,<ref name=Namibiainselbergreport>{{cite web |url=http://www.nbri.org.na/sites/default/files/Agricola1998_99_No10_07_de_Pauw_et_al.PDF |title=Production of an agro-ecological zones map of Namibia (first approximation) |website=nbri.org.na}}</ref> the interior of Angola,<ref name=InselbergAngola>{{cite web |url=https://library.wur.nl/isric/fulltext/isricu_i27864_001.pdf |title=Development of a soil and terrain map/database for Angola |access-date=2016-07-11 |archive-date=2021-03-09 |archive-url=https://web.archive.org/web/20210309024343/https://library.wur.nl/isric/fulltext/isricu_i27864_001.pdf |url-status=dead }}</ref> and the northern portions of Finland<ref>{{cite journal |last1=Kaitanen |first1=Veijo |title=Problems concerning the origin of inselbergs in Finnish Lapland |journal=Fennia |date=1 February 1985 |volume=163 |issue=2 |pages=359–364 |url=https://fennia.journal.fi/article/view/9075 }}</ref><ref>{{cite journal |last1=Ebert |first1=K. |last2=Hall |first2=A. |last3=Hättestrand |first3=C. |last4= Alm |first4=G. |date=2009 |title=Multi-phase development of a glaciated inselberg landscape |journal=Geomorphology |volume=115 |issue=1 |pages=56–66|doi=10.1016/j.geomorph.2009.09.030 }}</ref> and Sweden.<ref>{{cite journal |author-link=Sten Rudberg |last=Rudberg |first=S. |year=1988 |title=Gross morphology of Fennoskandia: Six complementary ways of explanation |journal=Geografiska Annaler |series=A. Physical Geography |volume=70 |issue=3 |pages=135–167 |doi=10.2307/521068 |jstor=521068}}</ref>{{efn-ua|Albeit its not the usual way of describing it the strandflat of Norway was held by Julius Büdel to be an etchplain with inselbergs.<ref name=Odleivetal2013>{{cite journal |last1=Olesen |first1=Odleiv |last2=Kierulf |first2=Halfdan Pascal |last3=Brönner |first3=Marco |last4=Dalsegg |first4=Einar |last5=Fredin |first5=Ola |last6=Solbakk |first6=Terje |date=2013 |title=Deep weathering, neotectonics and strandflat formation in Nordland, northern Norway |journal=Norwegian Journal of Geology |volume=93 |pages=189–213 |url=https://www.geologi.no/images/NJG_articles/NJG_3_4_Vol93_3_Olesen_scr.pdf |s2cid=226225485 }}</ref>}} [[File:Bahia Scenery en route to Salvador - Brazil - 01.jpg|thumb|Inselberg in the state of Bahia, northeastern Brazil]] The types of rock of which inselbergs are made include granite, gneiss and gabbro.{{efn-ua|Cliff Ollier has noted that in Uganda inselbergs are commonly made of granite rock, sometimes of gneiss and never of amphibolite or volcanic rock.<ref name=Zeit1960>{{Cite journal|title=The Inselbergs of Uganda |journal=Zeitschrift für Geomorphologie|last=Ollier|first=C.D.|volume=4|pages=43–52|issue=1|year=1960|author-link=Cliff Ollier}}</ref> According to Ollier protuding quartzite hills tend to form ridges rather than "true inselbergs".<ref name=Zeit1960/> Dundret in northern Sweden is made of gabbro.<ref>{{cite journal |last1=Ebert |first1=Karin |last2=Hall |first2=Adrian M. |last3=Hättestrand |first3=Clas |date=2012 |title=Pre-glacial landforms on a glaciated shield: The inselberg plains of northern Sweden |journal=Norwegian Journal of Geology |volume=92 |issue= |pages=1–17|doi= }}</ref>}}

===Origin and development=== {{expand section|date=October 2022|small=no}} 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."<ref>{{Cite book |title=Tropical Geomorphology |last=Thomas |first=Michael |publisher=The Macmillan Press Ltd. |year=1974 |isbn= |pages=136}}</ref> Volcanic or other processes may give rise to a body of rock resistant to erosion, inside a body of softer rock such as limestone, which is more susceptible to erosion. When the less resistant rock is eroded away to form a plain, the more resistant rock is left behind as an isolated mountain. The strength of the uneroded rock is often attributed to the tightness of its jointing.<ref>"A Dictionary of Ecology" (2004). Encyclopedia.com. Retrieved November 28, 2009</ref>{{efn-ua|{{harvtxt|Twidale|1981}} "Granitic Inselbergs: …"<ref>{{cite journal |last=Twidale |first=C.R. |author-link=Charles Rowland Twidale |title=Granitic Inselbergs: Domed, Block-Strewn and Castellated |journal=The Geographical Journal |volume=147 |issue=1 |year=1981 |pages=54–71 |jstor=633409 |doi=10.2307/633409 |bibcode=1981GeogJ.147...54T }}</ref> 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.}}

Inselbergs can be reshaped by ice sheets much the same way as roches moutonnées. In northern Sweden, examples of this type of inselberg are called ''flyggbergs''.<ref name="BennEvans">{{cite book |first1=Douglas |last1=Benn |first2=David |last2=Evans |title=Glaciers & Glaciation |publisher=Arnold |location=London, UK |edition=1st |year=1998 |isbn=978-0-340-58431-6}}</ref>{{rp|326–327}}<ref>{{cite book |last1=Lidmar-Bergström |first1=Karna|author-link=Karna Lidmar-Bergström |last2=Olvmo |first2=Mats |title=Plains, Steps, Hilly Relief and Valleys in Northern Sweden--review, Interpretations and Implications for Conclusions on Phanerozoic Tectonics |date=2015 |isbn=978-91-7403-308-3 |oclc=943395499 |url=http://resource.sgu.se/produkter/c/c838-rapport.pdf |publisher=Sveriges geologiska undersökning (Geological Survey of Sweden) |page=13 |access-date=June 29, 2016 |df=dmy-all}}</ref>

== Ecology == [[File:Kopje-1001.jpg|thumb|Lion atop a koppie in the Serengeti, northern Tanzania]] Inselbergs harbor unique and often endemic species from many taxonomic groups and can serve as refugia for animal species living in the surrounding matrix. Plant communities in these ecosystems are often adapted to extreme conditions such as high solar radiation and water scarcity due to the shallow and rocky soils. Since these species have a restricted distribution, they may also become severely threatened by invasive species.<ref name="Moreira2025">{{cite journal | last1 = Moreira| first1 = Fernanda G. L.| last2 = Carvalho| first2 = Fernanda A.| last3 = De Paula| first3 = Luiza F. A.| title = Non-native plant species on inselbergs of Brazilian tropical forests: Checklist and insights for biodiversity management and conservation| journal = Neotropical Biology and Conservation| date = 2025| volume = 20| issue = 3| pages = 255–280| doi = 10.3897/neotropical.20.e156777 | doi-access = free}}</ref>

The inselbergs of Eastern Africa tend to be a refuge for life in the Serengeti of Tanzania and in the Masai Mara of Kenya. 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 the lion, the hyrax, and an abundance of bird and reptile life.{{Citation needed|date=September 2025}}

On many tropical inselbergs, bare granite and gneiss surfaces are densely colonised by cyanobacteria and cyanobacterial lichens, which form dark biofilms and crusts that can be more conspicuous than vascular plants at ground level; a study in the Ivory Coast recorded 23 cyanobacterial species from 10 genera and 17 cyanobacterial lichen species from six genera on exposed rock across savanna, transitional and rainforest zones, with several ''Peltula'' species forming extensive brown crusts. In drier savanna regions with a several-month dry season, ''Peltula'' lichens reach their greatest abundance and species richness and largely cover the rock, whereas towards more humid savanna and rainforest climates the number of lichen species decreases and filamentous and sheathed cyanobacteria such as ''Scytonema'', ''Stigonema'' and ''Gloeocapsa'' become dominant, producing a black patina on the rock; these poikilohydric organisms tolerate prolonged desiccation and resume photosynthesis only when liquid water is present on the surface. Cyanobacteria and cyanobacterial lichens promote physical and chemical weathering (including surface alkalisation) and generate loose mineral material that accumulates with dead thalli around the base of the outcrops, and measurements on inselberg–savanna transects in tropical South America have shown higher nitrogen concentrations in topsoils adjacent to inselbergs than in the surrounding savanna, consistent with nitrogen fixation by the rock-dwelling cyanobacteria and with the relatively luxuriant growth of trees and shrubs in the immediate vicinity of some inselbergs.<ref name="Büdel et al. 1997">{{cite journal |last1=Büdel |first1=B. |last2=Becker |first2=U. |last3=Porembski |first3=S. |last4=Barthlott |first4=W. |title=Cyanobacteria and cyanobacterial lichens from inselbergs of the Ivory Coast, Africa |journal=Botanica Acta |volume=110 |issue=6 |year=1997 |doi=10.1111/j.1438-8677.1997.tb00663.x |pages=458–465}}</ref>

==Gallery== <gallery mode="packed" heights="150"> File:Mulanje Mountain.JPG|Mount Mulanje, a large inselberg in southeastern Malawi File:Ledang 1.jpg|Mount Ledang, a large inselberg in the state of Johor, Malaysia File:Kunak Sabah Mount-Madai-03.jpg|Mount Madai, Sabah, Malaysia File:Houtkop en R26-roete, Reitz-Daniëlsrus, Vrystaat.jpg|Houtkop, a {{convert|170|m|ft|abbr=|adj=on}} outcrop of Drakensberg basalt in the Free State, South Africa File:Amazon jungle from above.jpg|An inselberg in the rainforest of Suriname File:De Yalgo a Dori Marco Schmidt 0922.jpg|A duricrust inselberg near Dori, Burkina Faso File:Petermann Ranges (AU), Uluru-Kata Tjuta National Park, Uluru -- 2019 -- 3704-8.jpg|Uluru, an {{convert|863|m|ft|abbr=|adj=on}} sandstone formation in Australia's Northern Territory File:Devils Tower.jpg|Devils Tower, an archetypal example of an inselberg in Wyoming, US File:Vinyard Knob (960) 19-10-19 996.jpg|Vinyard Knob (high point 960') in the central portion of the Knobs Region of Kentucky File:Bernal.jpg|Peña de Bernal in Bernal, Querétaro, México File:Luosto ilmasta.jpg|Luosto, Lapland, Finland File:Rocca di Cavour dal Monte Cucetto.jpg|Rocca di Cavour, Piedmont, Italy File:Breast-Shaped Hill.jpg|An inselberg in Western Sahara File:Peñón de Guatapé 02.jpg|Peñón de Guatapé, Antioquia Department, Colombia File:Shiprock.snodgrass3.jpg|Shiprock, New Mexico </gallery>

== See also ==  * {{annotated link|Bornhardt}} * {{annotated link|Caprock}} * {{annotated link|Dissected plateau}} * {{annotated link|List of inselbergs}} * {{annotated link|Mesa}} * {{annotated link|Mogote}} * {{annotated link|Sky island}} * {{annotated link|Table (landform)}} * {{annotated link|Tuya}}

== Notes == {{notelist-ua}}

== References == {{reflist|30em}}

== External links == {{Commons category|Inselbergs}} * {{Cite EB1911|wstitle=Monadnock}}

Category:Inselbergs Category:Rock formations Category:Erosion landforms Category:Weathering landforms Category:Mountain geomorphology