Nobby Islet (also known as Knobby Island and Nobby Island) is an

islet An islet is a very small, often unnamed island. Most definitions are not precise, but some suggest that an islet has little or no vegetation and cannot support human habitation. It may be made of rock, sand and/or hard coral; may be permanen ...

located in the

Great Australian Bight The Great Australian Bight is a large oceanic bight, or open bay, off the central and western portions of the southern coastline of mainland Australia. Extent Two definitions of the extent are in use – one used by the International Hydrog ...

off the south coast of

Kangaroo Island Kangaroo Island, also known as Karta Pintingga (literally 'Island of the Dead' in the language of the Kaurna people), is Australia's third-largest island, after Tasmania and Melville Island. It lies in the state of South Australia, southwest ...

in the

Australian state The states and territories are federated administrative divisions in Australia, ruled by regional governments that constitute the second level of governance between the federal government and local governments. States are self-governing ...

South Australia South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest o ...

approximately south-west of Kingscote. It is currently part of the

Seal Bay Conservation Park Seal Bay Conservation Park is a protected area located on the south coast of Kangaroo Island in the Australian state of South Australia. It is the home of the third largest Australian sea lion colony in Australia. It is one of the most popula ...

Description

Nobby Islet is approximately south-west of Kingscote and about east of Point Ellen in Vivonne Bay and within 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 high and has an area of . The islet is difficult to access due to its location in shallow water adjoining a

cliffed coast A cliffed coast, also called an abrasion coast, is a form of coast where the action of marine waves has formed steep cliffs that may or may not be precipitous. It contrasts with a flat or alluvial coast. Formation In coastal areas in whic ...

line 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 A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attribu ...

to access the islet's summit.

Formation, geology and oceanography

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 Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...

known as Bridgewater Formation

calcarenite Calcarenite is a type of limestone that is composed predominantly, more than 50 percent, of detrital (transported) sand-size (0.0625 to 2 mm in diameter), carbonate grains. The grains consist of sand-size grains of either corals, shells, oo ...

. 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 A stack or sea stack is a geological landform consisting of a steep and often vertical column or columns of rock in the sea near a coast, formed by wave erosion. Stacks are formed over time by wind and water, processes of coastal geomorphology ...

. The islet is located in waters of a depth of about that partially conceal

wave-cut platform A wave-cut platform, shore platform, coastal bench, or wave-cut cliff is the narrow flat area often found at the base of a sea cliff or along the shoreline of a lake, bay, or sea that was created by erosion. Wave-cut platforms are often most o ...

s and that are subject to rolling seas.

Flora and fauna

As of 1996, the cliff faces were relatively un-vegetated. The islet's summit was occupied by clumps of Coast tussock-grass with a fringing

shrubland Shrubland, scrubland, scrub, brush, or bush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity. It ...

dominated by Coast Daisy-bush. The 25 other species were identified including Dry land Tea-tree,

Coast Beard-heath ''Leucopogon parviflorus'', commonly known as coast beard-heath or native currant, is a shrub or small tree in the family Ericaceae. It is native to all Australian states and territories excluding the Northern Territory and the ACT and also g ...

, Common correa,

Cotton bush ''Maireana aphylla'', also known as cotton bush or leafless bluebush, is a leafless (or almost leafless) shrub that is endemic to Australia. It is usually rounded in form and grows to around in height. The species occurs in all mainland sta ...

, Thyme Riceflower, pointed twinleaf, Black-anther Flax Lily,

Common Wallaby Grass ''Rytidosperma caespitosum'', known by various common names including common wallaby-grass, ringed wallaby-grass, and white-top, is a species of grass native to southern parts of Australia. Description It is a tufted perennial grass that reache ...

and Downy Dodder-laurel. The only animal life observed in 1996 was an

Osprey The osprey (''Pandion haliaetus''), , also called sea hawk, river hawk, and fish hawk, is a diurnal, fish-eating bird of prey with a cosmopolitan range. It is a large raptor reaching more than in length and across the wings. It is brown o ...

nest located on the islet's northern side,

white-faced storm petrel The white-faced storm petrel (''Pelagodroma marina''), also known as white-faced petrel is a small seabird of the austral storm petrel family Oceanitidae. It is the only member of the monotypic genus ''Pelagodroma''. Description The white-faced ...

s which were nesting in shallow burrows located over the entire summit and two species of

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia altho ...

- the

marbled gecko ''Christinus'' is a genus of Gekkonidae geckos found in southern regions of Australia. It contains species and subspecies that are regionally termed as marbled geckos. The contrasted patterns of these geckos, marbling, are found in a variety of ...

and the bull skink.

Protected areas status

Nobby Islet originally obtained

protected area Protected areas or conservation areas are locations which receive protection because of their recognized natural, ecological or cultural values. There are several kinds of protected areas, which vary by level of protection depending on the ena ...

status as a fauna reserve under the former ''Fauna Conservation Act 1964'' and then as a fauna conservation reserve declared under the ''Crown Lands Act 1929-1966'' on 16 March 1967. Since 1971, the waters surrounding the islet have been part of the

Seal Bay Aquatic Reserve __NOTOC__ Seal Bay Aquatic Reserve was a marine protected area in the Australian state of South Australia located in waters off the south coast of Kangaroo Island immediately adjoining and including the intertidal zone within the locality of Se ...

. As of 1996, it was described as being included in Seal Bay Conservation Park. As of 2012, the waters surrounding its shores are part of a restricted access zone located within the boundaries of the

Southern Kangaroo Island Marine Park __NOTOC__ Southern Kangaroo Island Marine Park (formerly Southern Kangaroo Island Commonwealth Marine Reserve) is a marine protected area located south of South Australia in waters within the Australian Exclusive economic zone to the south of ...

References

{{DEFAULTSORT:Nobby Island Islands of South Australia Uninhabited islands of Australia Kangaroo Island Stacks of Australia