A bornhardt () is a dome-shaped, steep-sided, bald rock

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets. Features Outcrops do not cover the majority of the Earth's land surface because in most p ...

ping 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 first described the feature. While ''bornhardt'' was originally used to sometimes denote a type of

inselberg An inselberg or monadnock ( ) is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain. In Southern Africa, a similar formation of granite is known as a koppie, an ...

(literally island mountain—an isolated dome in an otherwise flat landscape), the term ''bornhardt'' is used in modern literature to refer to domed hills and mountains regardless of isolation; thus, not all bornhardts are inselbergs and not all inselbergs are bornhardts. Bornhardts are commonly composed of

igneous rock Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

s, often

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

s, but examples of gneiss, quartzite and arkose bornhardts exist. The Sugarloaf Mountain of

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is a typical example of this landform and is the origin of the common bornhardt nickname "sugar loaf". Bornhardts are most easily seen in arid and semi-arid regions, but occur over a wide range of climates. Bornhardts are found in diverse topographic settings. They mainly occur in Multicyclic landscapes, or landscapes which underwent two or more cycles of erosion. Over geological time, bornhardts may degrade to form other landforms such as nubbins (or knolls) and castle koppies. Bornhardts were previously thought of as characteristically tropical landforms, but have been shown to be more related to lithology and rock structure than climate. Depending on their shape, they are also referred to as sugar loaves, whalebacks, turtlebacks or domes. In certain locales they may be 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 Central Australia, also sometimes referred to as the Red Centre, is an inexactly defined region associated with the geographic centre of Australia. In its narrowest sense it describes a region that is limited to the town of Alice Springs and ...

. Bornhardts commonly show extensive sheet jointing (fracture systems in the rock parallel to its surface). There are two main theories on the origins of bornhardts, each relating to jointing. The ''exogenetic'' theory asserts that sheet jointing is formed in response to the emerging topography, while the ''endogenetic'' theory suggests that the topography in bornhardts reflects already existing sheet jointing.

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