Saddleback Mountain volcanic origins

Kiama has much to owe to its volcanic past – its dramatic scenery and unique geological formations, and the abundant natural resources that allowed first the Wodi Wodi and then European settlers to flourish here.

The llIawarra escarpment is one of the most striking features of the NSW coast, running like a great unbreached wall for some 120 km and dominating the narrow strip of coastline below. The escarpment started to form at the end of the Triassic period (180-200 million years ago) when layers of rock from the Sydney Basin rose upwards and warped towards the south and southeast, and were further shaped by erosion for the past 30 million years.

The section of escarpment that runs between Kiama and Gerringong is particularly dramatic, with the mountains running directly down to the coast and crowned by Saddleback Mountain, rising some 600 metres above sea level. Kiama was the site of two strong volcanic flows, called the Gerringong Volcanics, which erupted from Saddleback 240 and 66 million years ago, and the distinct shape of Saddleback is formed from the remnants of an old volcanic plug or collapsed volcanic vent.

The rich volcanic soil in the Kiama area that resulted from these flows supported dense native rainforests, helping the Wodi Wodi to flourish here for thousands of years. The native cedar trees also attracted the first Europeans to the area, who rapidly logged the valuable timber and cleared much of the forest to establish the area’s productive dairy farming industry.

European settlers soon identified the potential in Kiama’s basalt deposits (igneous rock formed from the rapid cooling of lava rich in magnesium and iron), and constructed quarries to provide blue metal for much of the colony’s roads and railways, some of which are still active today. Tourism is also an important industry today, and our most iconic landmark, the Kiama Blowhole, is there thanks to the erosion process of columnar basalt or latite.

So next time you glance up at ancient Saddleback Mountain, take a moment to imagine all that has come to pass and all that is yet to come

Looking towards Saddleback Mountain c.1910s/20s

Men breaking basalt rock by hand in the State Quarry, Terralong St c.1880s

The ocean entrance to the Kiama Blowhole, where you can see how the ocean has eroded a path through the volcanic latite rock.

View of Saddleback Mountain c.1960s