Roter Kamm and Gross Brukkaros are two circular structures which at first sight might appear to have a similar origin. This is not the case. Roter Kamm, which lies in the Sperrgebiet, developed in 1,200 million year old Precambrian granitic rocks as a result of meteorite impact in the Pliocene c 3.7–5 million years ago. Gross Brukkaros is an impressive and isolated hill near Berseba, whose formation began towards the end of the Cretaceous c 75 million years ago. It started with the intrusion of carbonatite-rich magma into the Nama sediments that then covered this part of Namibia. The Brukkaros inselberg has since been brought into landscape prominence by downwearing of the surrounding surface.