the type of rock of the reef is of some importance, as it influences the range of possibilities for the local topography, which in turn influences the range of habitats provided, and therefore the diversity of inhabitants. sandstone and other sedimentary rocks erode and weather very differently, and depending on the direction of dip and strike, and steepness of the dip, may produce reefs which are relatively flat to very high profile and full of small crevices. these features may be at varying angles to the shoreline and wave fronts. there are fewer large holes, tunnels and crevices in sandstone reefs, but often many deep but low near-horizontal crevices.