Inselbergs

An inselberg, from the German for island mountain, is an isolated hill or mountain that rises abruptly from a surrounding plain or peneplain. Inselbergs are conspicuous in many landscapes and are especially common in arid and semi-arid regions, where long exposure to weathering and erosion emphasizes relief.

They form through differential erosion: once part of a larger, more uniform bedrock surface, a relatively resistant rock mass—often granite, granitic gneiss, quartzite, or basalt—withstands decay longer than surrounding rock. Over long timescales, the softer rock is removed by weathering, breakage, and erosion, leaving the resistant block perched above the landscape. In some settings inselbergs are remnants of an ancient peneplain, while in others they reflect localized tectonic uplift followed by erosion.

Morphologically, inselbergs typically have steep, cliff-like sides and a comparatively flat or rounded summit. The exposed bedrock is often bare, with sparse soil and sparse vegetation, though microhabitats can support specialized flora and fauna on shaded faces or sheltered hollows.

Geographically, inselbergs occur worldwide, but their striking, isolated forms are especially characteristic of Africa's landscapes and of others in Australia and South America. In the United States and some other regions, isolated rock outcrops of this kind are sometimes referred to as monadnocks, a term used interchangeably in some contexts with inselberg.