ase " ▁to ▁indicate ▁it ▁was ▁an ▁area ▁of ▁natural ▁bush ▁which ▁was ▁not ▁en closed ▁by ▁f ences . ▁ ▁Ge ology ▁ ▁Ku - ring - g ai ▁Ch ase ▁is ▁part ▁of ▁the ▁Horn s by ▁Pl ate au , ▁a ▁massive ▁block ▁of ▁sand stone ▁til ting ▁up wards ▁to ▁the ▁north . ▁The ▁park ▁compr ises ▁a ▁plate au ▁with ▁an ▁elev ation ▁of ▁generally ▁ 1 5 0 – 2 0 0 ▁m ▁above ▁sea ▁level . ▁The ▁plate au ▁is ▁divided ▁into ▁separate ▁sections ▁by ▁the ▁ste ep ▁valle ys ▁of ▁Cow an ▁Creek , ▁Co al ▁and ▁Cand le ▁Creek , ▁and ▁Smith s ▁Creek . ▁These ▁" f lo oded " ▁or ▁" d rown ed " ▁valle ys , ▁known s ▁as ▁r ias , ▁were ▁er oded ▁into ▁the ▁sand stone ▁much ▁deeper ▁than ▁the ▁current ▁sea ▁level ▁during ▁the ▁gla cial ▁phases ▁of ▁the ▁Ple ist oc ene ▁ice ▁age . ▁When ▁the ▁ice ▁caps ▁m elt ed ▁about ▁ 1 0 , 0 0 0 ▁years ▁ago , ▁the ▁sea ▁levels ▁rose ▁and ▁flo oded ▁the ▁valle ys ▁of ▁the ▁park . ▁ ▁The ▁dominant ▁rock ▁type ▁is ▁Haw kes bury ▁Sand stone ▁which ▁determ ines ▁the ▁top ography ▁and ▁the ▁veget ation ▁in ▁the ▁sand y ▁so ils . ▁Sand stone ▁cl iffs , ▁rock y ▁and ▁out cro ps , ▁and ▁worn ▁c aves ▁are ▁common ▁throughout ▁the ▁park . ▁Ind igen ous ▁people ▁eng ra ved ▁the