 The cliff formations are punctuated by large gorges, the result of eroded basalt dykes which formed in the sedimentary rock in the early Tertiary period.The sandy soils are covered with diverse vegetation comprising over 350 species once common in the eastern suburbs of Sydney including rare species and communities.The most common vegetation cover is heath Banksia community ("Banksia ericofolia"), prickly tea tree ("Leptospermum juniperinum") and paperbark ("Melaleuca nodosa").