Kiama was the site of two strong volcanic flows, called the Gerringong Volcanics, which came out of Saddleback Mountain, now a collapsed volcanic vent. The Kiama Blowhole is part of an erosion process on the more recent rock, formed into columnar basalt, or latite. Before the cedar-getters (comprising ex-convicts, convicts and runaways, some with cedar licences and many without) arrived in the area around 1810, the local Indigenous Australians, Wodi Wodi of the language group Dharawal, had been using the land for thousands of years, moving every six weeks or so in family groups. This is supported by a midden of shells at nearby Bass Point used for more than 17,000 years. During this time the whole coastal hills was covered in rainforest and cedar brush. There is evidence of a flourishing culture with intricate possum cloaks, a developed song and story cycle, and a deep understanding of the many plants of the rainforest. Only a few remnants of rainforest survive along the escarpment in places like the Minnamurra Rainforest Centre.
