The term mons, like other terms of planetary nomenclature, describes only the external view of the feature, but not its origin or geological structure. It is used for mountains of any origin, and objects in this class are very diverse. Usually they are results of tectonic, impact or volcanic processes. Examples of such mountains are the Maxwell Montes on Venus, the Montes Apenninus on the Moon and Olympus Mons on Mars, respectively. More unusual origins are also possible. For example, the Geryon Montes of Mars are an erosional remnant of a former plateau within Ius Chasma, part of the Valles Marineris canyon system.