South Australia's south east cluster of 20 water-filled ancient sinkholes a major diving attraction

The concentration of water-filled sinkholes in South Australia's south east, near Mount Gambier, has attracted worldwide attention.
Image courtesy ABC

South Australia’s south-east Limestone Coast region around Mount Gambier has about 50 sinkholes, one of Earth’s largest concentrations. Twenty of those sinkholes are cenotes: filled with water, because they're below the water line.

The sinkholes have been formed from the Limestone Coast’s long-term exposure to ocean water and waves that have created many large caves, with their entrances blocked off by erosion and caveins. When the ceiling of the cave collapses, a sinkhole is formed.

Fossil Cave (formerly The Green Waterhole), at Tantanoola, about 22 kilometres from Mount Gambier, is largely filled with water and, during the 1960s-80s, divers from the South Australian Museum, South Australian Underwater Speleological Society, Flinders University Underwater Club and Allum and Garrad first surveyed the 30-million-year old Oligocene coralline limestone site.

Pleistocene subfossil material of birds and mammals, from 15,000 to 40,000 years ago, was found to a depth of about 15 metres. The fossils represent many living animals but also extinct species including the birds Centropus colossus and Orthonys hypsilophus, mammals Thylacinus cynocephalus and Propleopus oscillans, Macorpus titan and kangaroos Procoptodon gilli and Simosthenurus occidentalis.

Access for cave diving is limited to holders of the Cave Divers Association of Australia’s advanced grade. The association has also worked closely with the fourth-generation Kilsby family whose sheep farm near Mount Gember is home to one of the deepest and clearest sinkholes, renowned worldwide. The family has welcomed divers since the 1950s and the Kilsby sinkhole is used for South Australian police divers annual exercises. It has even by used by the federal government for weapons research into sonobouy monitors.

Other water-filled sinkholes near Mount Gamier include the three at Ewen Ponds, and the Little Blue Lake. Not water-filled, but another south-east sinkhole attraction, is the Umpherston, also near Mount Gambier, that has become a spectacular sunken garden.

 

Other related ADELAIDEAZ articles

Mount Gambier's Blue Lake an enigmatic legacy of volcano from 28,000-6,000 years ago

The Blue Lake is one of four shallow volcanic crater lakes near Mount Gambier (named after the extinct volcano) on south-east South Australia’s Limestone Coast. Only two of the lakes remain; Leg of Mutton and Brown dried up over 30 to 40 years as the water table dropped. Dates for the volcano’s eruption vary from 28,000 years to 6,000 years ago – which would make it the most recent on the Australian mainland. Blue Lake’s average depth is 72 metres but a natural cave section could take its deepest point to 204 metres. Early each November, the lake's sombre blue during winter changes to an intense deep turquoise blue almost overnight. This colouring remains until late February, when it gradually changes. From late March, it returns to a distinct sombre blue. Cause of this phenomenon is still up for conjecture but likely it involves the warming of the surface layers of the lake during the summer to around 20 °C causing calcium carbonate to precipitate out of the solution and enabling microcrystallites of calcium carbonate to form. This scatters the blue wavelengths of sunlight. An obelisk beside the lake marks poet Adam Lindsay Gordon’s daring feat in 1865 when he made his famed leap on horseback over an old post and rail guard fence onto a narrow ledge overlooking the Blue Lake and jumped back again onto the roadway. The 3.6 kilometre road and walking track around the Blue Lake gives access to many viewing points, the most popular being the underpass between the Blue Lake and the Leg of Mutton Lake.
 

Coorong, a haven for birdlife, created by sand dunes from 80,000 to 120,000 years ago

The Coorong, 152 km from Adelaide, is a set of complex and ancient sand dunes ranging from 80,000 to 120,000 years ago. The modern Coorong was formed between 6,000 and 20,000 years ago when the sea rose to form an island on top of the 80,000-year-old dune. This produced a lagoon behind the present line of seaward dunes. Many access points from the sea to the lagoon were filled over time by wind and the sands to create a narrow neck of sand dunes stretching 130km along the south-east coast of South Australia. The Coorong has some of Australia’s most spectacular birdlife around its series of mudflats, low-lying vegetation and lakes. Huge cranes, swans, pelicans, sandpipers, terns, white-faced herons, ibis, kites, galahs, rosellas, wattlebirds and currawongs join the variety of freshwater and saltwater birds. About 240 species of bird use The Coorong as their home. Some migrate from as far away as Siberia, China and Japan. Its fauna includes western grey kangaroos, echidnas, wombats, possums, snakes and the waters are still rich in mulloway, mullet and bream. Five Aboriginal tribal groupings – the Ngarrindjeri – lived on The Coorong (named from the local Aboriginal word “kurangh” for “neck”). They made bark and reed canoes, lived on the fish and molluscs in the area, and built shelters against the cold Southern Ocean winds. They were decimated by the arrival of Europeans, bringing smallpox, that raged all along the Murray River, and massacres that cut their numbers from about 3200 in 1842 to 511 by 1874. 

Orangutan George's popularity lacking awareness of the toll on animals' wellbeing

George the orangutan (1950-76) was a prime example of Adelaide Zoo animals that became crowd favourites. Another was Percy the chimpanzee during the 1950s in the tradition of Newsboy the hippopotamus from the 1930s. But this popularity – reflecting the 1960s slogan “Visit the Zoo: Laugh and Learn” – masked a lack of awareness of the damage to the animals' physical and psychological wellbeing. When two Galapagos tortoises arrived from San Diego Zoo in 1972, rides of their backs became standard entertainment for child visitors. 

 

Supervolcano of Gawler Ranges 1.6 billion years ago leaves the legacy of Olympic Dam ore riches

The remnants of a supervolcano found in the Gawler Ranges of South Australia drawfs the Yellowstone Caldera, the largest active supervolcano today on Earth. Gawler Ranges, stoney hills to the north of Eyre Peninsula, were formed by the supervolcano nearly 1.6 billion years ago. It spread a lava field 500 kilometres in diameter and up to 300 metres thick. The total lava was as high as 500,000 cubic kilometres – enough to fill Sydney Harbour a million times over. The lava reached temperatures above 1,000 degrees Celsius and erupted from the volcano almost instantaneously. The phenomenon left the world's largest hydrothermal deposit: a spectacular ore system with huge reserves of copper, uranium, silver and gold. Olympic Dam mine area, with about nine billion tonnes of ore, and OZ Minerals’ Carrapateena project are extracting the bounty of these hugely enriched ore-forming volcanic fluids. Bornhardts – dome-shaped steep bald rock outcrops – dominate the landscape of Gawler Ranges, traditional home of Gugada Aboriginal people. The ranges were given their European name by Edward John Eyre in honour of the South Australia's second governor George Gawler in 1839. On this expedition, Eyre made the first recorded sighting of South Australia's floral emblem: the Sturt desert pea. The 100-metre-wide sloping granite Coralbignie (Houlderoo) Rocks are another of the Gawler Ranges' features on the South Australian heritage register.

Monarto Zoo's new visitor centre part of Wild Africa expansion project with resort

A new $15.8 million visitor centre for Monarto Zoo, funded by the Australian and South Australian governments, was announced in 2019. The zoo's original visitor centre, built in 1997, has been struggling to cope with the rapid growth in attendance at Monarto, since 2014, that has reached 160,000 visitors each year. The new visitor centre will include a large indoor and outdoor café, nature play spaces, retail, visitor services, offices and improved car parking and access. The visitor centre is part of a bigger Wild Africa expansion project vision for a $50 million safari resort at Monarto Zoo, near Murray Bridge. It will give visitors the chance to stay at Monarto Zoo for the first time in a range of accommodation from safari-resort level to eco-luxe glamping tents. The visitor centre funding was expected to unlock another $35 million in private investment to develop the resort. The vision is for annual visitors to pass 220,000. The Wild Africa precinct proposal would exploit Monarto's ability to expand into an area bigger than all other Australian zoos put together. The 500ha expansion would take Monarto’s total area to 1500ha. Seventy thousand trees have been planted on the land that would become Wild Africa, and 4000 boxthorn plants, 280 rabbit warrens and all internal fences removed. The Wild Africa precinct’s first animal resident in 2019 was southern white rhino male Ibutho. Weighing more than 2.2 tonnes, Ibutho was moved by crane and truck from his enclosure at Monarto Zoo into his new home, destined to become a sanctuary to a crash of 30 rhinos.

Contact Us

We welcome positive constructive feedback