geomorphology Geomorphology () is the scientific study of the origin and evolution of topographic and bathymetric features generated by physical, chemical or biological processes operating at or near Earth's surface. Geomorphologists seek to understand wh ...

a nubbin is a small and gentle hill consisting of a

bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of bed ...

core dotted with rounded residual

block Block or blocked may refer to: Arts, entertainment and media Broadcasting * Block programming, the result of a programming strategy in broadcasting * W242BX, a radio station licensed to Greenville, South Carolina, United States known as ''96.3 ...

s. The blocks derive from disintegrated and

weathered ''Weathered'' is the third studio album by American rock band Creed, released on November 20, 2001. It was the last Creed album to be released until '' Full Circle'' came out in October 2009, with Creed disbanding in June 2004. It is the only Cr ...

bedrock layers. In particular it is assumed that the boulders of the nubbins are the remnants of the outer one or two exfoliation shells that weathered underground - albeit some weathering can continue to occur once the boulders are exposed on surface. Nubbins form in a similar way to castle koppies and

bornhardt A bornhardt () is a dome-shaped, steep-sided, bald rock outcropping at least in height and several hundred metres in width. They are named after Wilhelm Bornhardt (1864–1946), a German geologist and explorer of German East Africa, who firs ...

s, and the three landforms can be seen as different expressions of the same phenomena. Nubbins occur often in patterned groups. Nubbins can be found in humid

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

- and monsoon-climate areas. According to geomorphologist C. R. Twidale this is the environment where most nubbins form. Nubbins outside the humid or seasonally-humid tropics are relict landforms formed in a humid and tropical past or form in areas of high subsurface humidity. Examples of localities with nubbins include the

Southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural list of regions of the United States, region of the United States that includes Arizona and New Mexico, along with adjacen ...

, the

MacDonnell Ranges The MacDonnell Ranges, or Tjoritja in Arrernte language, Arrernte, is a mountain range located in southern Northern Territory. MacDonnell Ranges is also the name given to an Interim Biogeographic Regionalisation for Australia, interim Australia ...

in Central Australia and

Namaqualand Namaqualand ( Khoikhoi: "Nama-kwa" meaning Nama Khoi people's land) is an arid region of Namibia and South Africa, extending along the west coast over and covering a total area of . It is divided by the lower course of the Orange River int ...

in Southern Africa. While nubbins are typically made up of granite there have also been reports of nubbins made of

ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surrou ...

References

Geomorphology Erosion landforms Rock formations Weathering landforms {{erosion-stub

See also

References