One: Ela Elap Sinkhole

 

Cave divers preparing to brave Ela Elap, the coldest sinkhole in the South East of South Australia.

Photo: Leon Rademeyer

 

Ela Elap: The South East’s coldest and most haunting sinkhole

By Leon Rademeyer #5013

Known among cave divers as the coldest sinkhole in the South East, Ela Elap lies hidden in a paddock on private land at Mount Schank. Its water temperature sits at around 11°C - two to four degrees colder than most other water-filled caves and sinkholes in the region - giving it a reputation that both challenges and fascinates divers.

Sometimes called the Green Lake due to the grey-green hue of its water, Ela Elap spans roughly 35m across and reaches a depth of 50m on its north-eastern side. Its chilly water has been noted since early exploration, and a 1981/2 environmental research project by cave divers confirmed it to be the coldest of the local water-filled sinkholes studied at the time. The reason for its unusually low temperature remains unknown.

 

 

Weeping willow

One of the sinkhole’s most striking features is a massive weeping willow that once stood at the water’s edge. After toppling from its base, it crashed down the sinkhole’s 10m high walls and now rests beneath the surface. Its uprooted base lies at roughly 20m, with a tangle of branches stretching even deeper. When the site is undisturbed, the finer branches become coated in a white, algae-like film, giving the submerged tree an eerie, ghost-like appearance as divers descend.

The sinkhole is undercut around its entire perimeter except on the south-western side, where a sloping ramp was originally cut to allow stock access to the water. Directly beneath the overhang, divers reach the top of a rock pile at around 28m. From there the pile drops away to a soft silt floor scattered with additional fallen branches.

To the right of the entry zone, at a depth of 36m, divers encounter several tall vertical limestone structures. Some believe these pillars are likely microbialites - possibly stromatolites - which may have inspired long-circulated rumours of giant stalactites hidden within the sinkhole.

A cave diver exploring the giant weeping willow in the murky depths of the Ela Elap Sinkhole.

What’s in a name?

The origin of the name Ela Elap has been debated, but the most plausible explanation links it to local Aboriginal words meaning ‘lap lap,’ or small fish. Many divers jokingly assume it is an anagram for Pale Ale or Pale Hole, and some mistakenly refer to it as ‘Eloh Elap.’

History and geology

ELA Elap and two other nearby sinkholes – Little Blue Lake and One Tree - are in a line of special sinkholes (called cenotes) across the Mount Schank plain. They have formed from water dissolving large deep underground chambers along fractures of the geological Nelson Fault Line which runs from Nelson and the Piccaninnie Ponds area through Mount Schank and across the Kongorong limestone plains.

Early settlers thought the sinkholes were volcanic vents associated with Mount Schank eruptions, but geoscientists now know the groundwater was made acidic by deep volcanic gases which caused the large underground chambers to be dissolved within the limestone until their roofs fell in to form the sinkholes of today. Mount Schank is about 5000 years old, but the sinkholes are much older - between 30,000 to 130,000 years is a current estimate.

In 1844, Governor Grey’s early South East exploration expedition passed Little Blue Lake and the renowned colonial artist George French Angus painted several watercolours of sinkholes discovered. One of his paintings thought to be of Little Blue proved to be of Ela Elap as it shows Mount Schank closer in the background.

Both Ela Elap and Little Blue have large ramps cut at an angle down to the water for stock to drink with pick marks and engraved names in the walls indicating they were cut before 1900. The current water level is too low for stock to drink, but rainfall records show a very wet period for several decades around the 1900s.

Earliest recorded dive

The sinkhole was described by Deputy Surveyor General Thomas Burr in 1845 and appeared in a report by the Cave Exploration Group of South Australia in April 1962. The earliest recorded dive took place in November 1962, when local divers explored the sinkhole to a depth of about 47m.

Today, Ela Elap remains one of the region’s most atmospheric and memorable dive sites - a cold, green, ghost-lit world where nature, geology, and history intertwine beneath the surface.

*Thank you to Ian Lewis #258 and Peter “Puddles” Horne #719 for their historical and geological insights.