Inselberg

An inselberg, also called a monadnock, is an isolated rock hill, knob, ridge or small mountain that rises abruptly from an otherwise gently sloping or nearly level plain. An inselberg forms when a body of rock more resistant to erosion, such as granite, sits within a surrounding body of softer rock that is worn down and lowered by differential erosion, leaving the harder rock standing; when the resulting hill is dome shaped and made of granite or gneiss it may also be called a bornhardt, though not every bornhardt qualifies as an inselberg.