The headland is composed of a black basaltic-looking volcanic rock called latite. Called the Blowhole Latite Member, it is up to 50 m thick and displays tall, well developed columns (visible around sea level at the Blowhole). It is exposed along the coast for about 11 km, dipping slightly to the north and dropping below sea level at Kiama. The eruption involved massive volumes of lava.
The volcanic flow sits on a formation called the Westley Park Sandstone Member, sometimes called the Westley Park Tuff because it contains lots of volcanic ash. This displays many sedimentary structures such as bedding, cross bedding and scour and fill—evidence of deposition from flowing water. The contact between the sandstone and the volcanic rock is highly irregular because the sediment and lava had mixed together. The sediment was obviously loose and wet when the lava erupted upon it. A mixture of lava and sediment like this is called peperite.
At the top of the Blowhole Latite Member, the overlying sediment has also mixed with lava forming peperite and this mixing can be seen alongside the path. The overlying member is called the Kiama Sandstone Member, or the Kiama Tuff. It is a prominent purplish, reddish sandstone up to 53 m thick, well exposed in road cuttings in the northern part of Kiama.
So, here we have the underlying sandstone deposited rapidly, not long before the thick lava was erupted, and that not long before the the overlying sandstone was deposited, all in the presence of abundant water. These three geological members could be described as contemporaneous with each other. Considering how quickly basaltic lava would crystalise in the presence of water, we are talking in terms of days or weeks at the most.
There is a time problem here but not for the biblical geologist. It is the uniformitarian geologists, who imagine these rocks formed over millions of years, who have the time problem. Where are they going to insert all those millions of years into these rocks?