Inselbergs

Abstract

Inselbergs1 are isolated rock outcrops in the palaeotropics and the neotropics coming up out of different vegetation of savannas or cerrados (Fig. 11.1A) or rainforests (Fig. 11.1B). In savannas with a certain savanna affinity of their flora they also have been described as “rock savanna”. They consist of monolithic blocks, mostly of granite or gneiss, of a considerable geological age, i.e. 10×10⁶ years at least and 40 – 50×10⁶ years on average. More rarely inselbergs may also consist of sandstone. They range from several tens or hundreds of meters high, the highest one found in French Guiana being 740m high (Schnell 1987). “Shield-type” inselbergs may have extensions of several square kilometers. In arid regions and deserts they may have been eroded to heaps of rather small rocks (Fig. 11.1D). Inselbergs evolve by deep and intensive weathering (Fig. 11.2A). Thus, inselbergs are really islands separated from the surrounding savanna or forest vegetation (Figs. 11.1A, B and 11.2B; Barthlott et al. 1993; Porembski and Barthlott 2000a). They provide very different ecological conditions.