Nobby Islet

Nobby Islet

View of Seal Bay looking west with Nobby Islet in background
Nobby Islet
Geography
Location	Great Australian Bight
Administration
Australia

Nobby Islet (also known as Knobby Island and Nobby Island) is an islet located in the Great Australian Bight off the south coast of Kangaroo Island in the Australian state of South Australia approximately 50 kilometres (31 miles) south-west of Kingscote. It is currently part of the Seal Bay Conservation Park.

Nobby Islet is approximately 50 kilometres (31 miles) south-west of Kingscote and about 9.2 kilometres (5.7 miles) east of Point Ellen in Vivonne Bay and within 200 metres (660 feet) of the coast at Seal Bay. The islet is reported as being cylindrical in shape with almost vertical sides and finished with a flat top. It is 75 metres (246 feet) high and has an area of 12 hectares (30 acres). The islet is difficult to access due to its location in shallow water adjoining a cliffed coastline that exposed to rolling seas and the fragile condition of its vertical cliff faces. A survey carried out by the responsible government agency in 1996 used a helicopter to access the islet’s summit.

Nobby Islet may have been formed as recently as 6000 years ago due to the relatively shallow depth of the water surrounding it. As of 1996, the islet is reported as appearing to be entirely composed of a limestone known as Bridgewater Formation calcarenite. It is also observed that there was recent evidence of rockfalls due to the crumbly consistency of the calcarenite and that debris cones were present on its relatively sheltered northern side while any collapsed materials on its southern face had been washed away by wave action. The islet’s summit was also reported as being ‘gently terraced by resistant layers of calcrete that retain bands of sandy soil’. Nobby Islet is technically a sea stack. The islet is located in waters of a depth of about 5.5 metres (18 feet) that partially conceal wave-cut platforms and that are subject to rolling seas.