Inselberg

An inselberg or monadnock (/məˈnædnɒk/ 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.[upper-alpha 1] 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.[2]

## Contents

* 1 Etymology
* 1.1 Inselberg
* 1.2 Monadnock
* 2 Definition
* 3 Geology
* 3.1 Geological and geographical patterns
* 3.2 Location
* 3.3 Origin and development
* 4 Ecology
* 5 Gallery
* 6 See also
* 7 Notes
* 8 References
* 9 External links

## Etymology

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.[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 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

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.[4] It is thought to derive from either menonadenak () or menadena ().[5] 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 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).[6]

## Definition

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.[7]

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,[8] though some authors have explicitly argued these terms are completely synonymous.[9]

## Geology

### Geological and geographical patterns

The Spitzkoppe of Namibia, a 670-metre (2,200 ft) granite peak formed by early Cretaceous rifting and magmatism.

Inselbergs are common in eroded and weathered shields.[10] 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.[11][12] By this association various inselberg fields in Africa and South America are assumed to be the vestiges of eroded etchplains.[13][14]

### Location

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,[15] the Anti-Atlas of Morocco,[13] Northeast Brazil,[16] Namibia,[17] the interior of Angola,[18] and the northern portions of Finland[19][20] and Sweden.[21][upper-alpha 2]

Inselberg in the state of Bahia, northeastern Brazil

The types of rock of which inselbergs are made include granite, gneiss and gabbro.[upper-alpha 3]

### Origin and development

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] 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.[25][upper-alpha 4]

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.[27]: 326–327 [28]

## Ecology

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.[29]

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.[30]

## Gallery

* Mount Mulanje, a large inselberg in southeastern Malawi

* Mount Ledang, a large inselberg in the state of Johor, Malaysia

* Mount Madai, Sabah, Malaysia

* Houtkop, a 170-metre (560 ft) outcrop of Drakensberg basalt in the Free State, South Africa

* An inselberg in the rainforest of Suriname

* A duricrust inselberg near Dori, Burkina Faso

* Uluru, an 863-metre (2,831 ft) sandstone formation in Australia's Northern Territory

* Devils Tower, an archetypal example of an inselberg in Wyoming, US

* Vinyard Knob (high point 960') in the central portion of the Knobs Region of Kentucky

* Peña de Bernal in Bernal, Querétaro, México

* Luosto, Lapland, Finland

* Rocca di Cavour, Piedmont, Italy

* An inselberg in Western Sahara

* Peñón de Guatapé, Antioquia Department, Colombia

* Shiprock, New Mexico

## See also

* Earth:Caprock
* Earth:Dissected plateau - Plateaus area that has been severely eroded so that the relief is sharp
* Earth:List of inselbergs
* Earth:Mesa
* Earth:Mogote - Steep-sided residual hill of limestone, marble, or dolomite on a flat plain
* Earth:Sky island - Geographic or environmental feature
* Earth:Table (landform) - Raised landform with a flat top
* Earth:Tuya - Flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet

## Notes

1. ↑ In Southern Africa, a similar formation of granite[citation needed] is known as a koppie, an Afrikaans word ("little head") from the Dutch diminutive word kopje.[1]
2. ↑ Albeit its not the usual way of describing it the strandflat of Norway was held by Julius Büdel to be an etchplain with inselbergs.[22]
3. ↑ Cliff Ollier has noted that in Uganda inselbergs are commonly made of granite rock, sometimes of gneiss and never of amphibolite or volcanic rock.[2] According to Ollier protuding quartzite hills tend to form ridges rather than "true inselbergs".[2] Dundret in northern Sweden is made of gabbro.[23]
4. ↑ (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

1. ↑ Webster's New Explorer Dictionary of Word Origins (2004). Federal Street Press: New York.
2. ↑ 2.0 2.1 2.2 Ollier, C.D. (1960). "The Inselbergs of Uganda". Zeitschrift für Geomorphologie 4 (1): 43–52.
3. ↑ Holmes, Arthur (1978). Holmes Principles of Physical Geology. Nelson. ISBN 978-0-17-771299-9.
4. ↑ Raymo, Chet and Raymo, Maureen E. (1989) Written in Stone: A Geologic History of the Northeastern United States. Globe Pequot, Chester, Connecticut.
5. ↑ "Vermont Soils with Names of American Indian Origin " United States Department of Agriculture, Natural Resources Conservation Service. Retrieved January 6, 2008.
6. ↑ Baldwin, Henry I. (1989). Monadnock Guide 4th edition. Concord, New Hampshire: Society for the Protection of New Hampshire Forests.
7. ↑ Young, Anthony (1969). Clayton, K.M.. ed. Slopes. Edinburgh: Oliver & Boyd. pp. 209.
8. ↑ Gerrard, John (1988). Rocks and Landforms Routledge: Florence, Kentucky.
9. ↑ King, Lester C. (1953). "Canons of landscape evolution". Geological Society of America Bulletin 64 (7): 721. doi:10.1130/0016-7606(1953)64[721:COLE2.0.CO;2].
10. ↑ 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. Bibcode: 2018BuGSF..90..239N.
11. ↑ "Summary: Inselbergs/Hills/Knobs". Knowledge Sciences, Inc.. http://www.tec.army.mil/research/products/desert_guide/lsmsheet/lsinsel.htm.
12. ↑ Easterbrook, Don J. (1999). "Chapter Three: Weathering". Surface Processes and Landforms (2nd ed.). Upper Saddle River, NJ: Prentice Hall.
13. ↑ 13.0 13.1 Guillocheau, 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". Gondwana Research 53: 82. doi:10.1016/j.gr.2017.05.015. Bibcode: 2018GondR..53...82G. https://hal-insu.archives-ouvertes.fr/insu-01534695/file/guillocheau-GondRes-2017.pdf.
14. ↑ García, Carolina; Hermelin, Michel (2016). "Inselbergs Near Medellín". in Hermelin, Michel. Landscapes and Landforms of Colombia. Springer. p. 219. ISBN 978-3-319-11800-0.
15. ↑ Sundborg, Å.; Rapp, A. (1986). Erosion and Sedimentation by Water: Problems and prospects. Ambio. pp. 215–225.
16. ↑ Maia, Rúbson Pinheiro; Frêgo Bezerra, Francisco Hilário; Leite Nascimento, Marcos Antônio; Sampaio de Castro, Henrique (2015). "Geomorfologia do Campo de Inselbergues de Quixadá, nordeste do Brasil" (in Portuguese). Revista Brasileira de Geomorfologia 16 (2): 651. doi:10.20502/rbg.v16i2.651. Bibcode: 2015RvBrG..16..651M.
17. ↑ "Production of an agro-ecological zones map of Namibia (first approximation)". http://www.nbri.org.na/sites/default/files/Agricola1998_99_No10_07_de_Pauw_et_al.PDF.
18. ↑ "Development of a soil and terrain map/database for Angola". https://library.wur.nl/isric/fulltext/isricu_i27864_001.pdf.
19. ↑ Kaitanen, Veijo (1 February 1985). "Problems concerning the origin of inselbergs in Finnish Lapland". Fennia 163 (2): 359–364. https://fennia.journal.fi/article/view/9075.
20. ↑ 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.
21. ↑ 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.
22. ↑ Olesen, Odleiv; Kierulf, Halfdan Pascal; Brönner, Marco; Dalsegg, Einar; Fredin, Ola; Solbakk, Terje (2013). "Deep weathering, neotectonics and strandflat formation in Nordland, northern Norway". Norwegian Journal of Geology 93: 189–213. https://www.geologi.no/images/NJG_articles/NJG_3_4_Vol93_3_Olesen_scr.pdf.
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.. pp. 136.
25. ↑ "A Dictionary of Ecology" (2004). Encyclopedia.com. 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. Bibcode: 1981GeogJ.147...54T.
27. ↑ Benn, Douglas; Evans, David (1998). Glaciers & Glaciation (1st ed.). London, UK: Arnold. ISBN 978-0-340-58431-6.
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. Sveriges geologiska undersökning (Geological Survey of Sweden). p. 13. ISBN 978-91-7403-308-3. OCLC 943395499. http://resource.sgu.se/produkter/c/c838-rapport.pdf. Retrieved June 29, 2016.
29. ↑ Moreira, Fernanda G. L.; Carvalho, Fernanda A.; De Paula, Luiza F. A. (2025). "Non-native plant species on inselbergs of Brazilian tropical forests: Checklist and insights for biodiversity management and conservation". Neotropical Biology and Conservation 20 (3): 255–280. doi:10.3897/neotropical.20.e156777.
30. ↑ Büdel, B.; Becker, U.; Porembski, S.; Barthlott, W. (1997). "Cyanobacteria and cyanobacterial lichens from inselbergs of the Ivory Coast, Africa". Botanica Acta 110 (6): 458–465. doi:10.1111/j.1438-8677.1997.tb00663.x.

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