|The cave is hard to access, ensuring people|
don't enter the cave alone and uninsured
While some people might be snoozing or comfortably slurping tea on a Sunday morning, Graeme Pilkinton is likely to be pulling on a jumpsuit, strapping on kneepads and testing the flashlight on his helmet.
Secretary of the Cave Exploration group of South Australia, he is one of around 100 committed cave explorers who spend their free time exploring, excavating and mapping the state's caves.
Out of sight, cave explorers are largely out of mind for most people, but many have put decades of effort into understanding what lies under SA.
The cavers discover and document everything from the collapse chamber systems near Naracoorte, to the deep channels of the Nullarbor, and the dendritic caves of the River Murray.
On the Yorke Peninsula, it is the Corna Lynn cave just a couple of kilometres out of Currumulka that continues to be passionately explored and extended.
Entering inside, it is a far different experience to the large, open walk-in and walk-out tourist caves.
In Corra-Lynn, cavers crouch and crawl through a complex series of narrow tunnels which run and intersect on different levels, and are connected vertically by fissures.
"To get from one level to the next, you go up and down these fissures, no one level of the cave is continuous, in this particular cave the levels are about six metres apart," Graeme said.
Graeme first entered the Corra-Lynn cave 41 years ago in 1971 when it was just three kilometres long, now it is 14km and the longest cave in the region.
"Most caves have a limited extent, they can't extend much more than they are the way the caves are formed, there's very little chance of you getting any bigger.
"Whereas this cave has nothing to stop it for kilometres."
More fossils and deeper fissures
Endless dirty and dark hours of volunteer exploration has revealed a variety of discoveries in Corra-Lynn.
These include rare fossil findings, stretching back five million years old- significantly older than the one million year old deposits found in other caves around the state.
"They're in a patch of history that doesn't have much in the way of fossil deposits," Graeme said.
He said there were remnants of animals like giant kangaroos, turtles, birds, thylacines, and even a wallaby with small horns on it.
However, it was not just the ancient fossil deposits that lured explorers, but the wider challenge of caving.
Curious engineers and geophysicists feature among the caving bunch, who thrive off carefully analysing the cave pattern and anticipating its structure to open up new parts.
"It's a really big high, finding something that's brand new that no one's ever been in to," said Graeme.
"It's its own drug and it's a better drug that any other."
Currently, members of the cave exploration group have been working to access another deeper series of tunnels in Corra-Lynn.
"You can't go down six metres to the next level, it's at least 12, we're just about 12 metres now and it looks like it might be doing something."
Conserving the caves
While early cavers used to traipse through new sections, increased focus on conserving the caves has made the task more considered.
Graeme said the attitudes of people caving have changed from haphazardly exploring for the thrill of it, to now ensuring the cave got priority.
"They didn't consider anything but their own enjoyment in the cave, but over a period of time those same people have gradually worked out that it's best to conserve the cave a bit.
"When we look at something we say, now what damage will we do to the cave, not, how fun this will be to travel through."
He said cavers also now had to survey the caves as they went along.
"One of the philosophies of our particular cave group was that if you find something or you've been in a cave, then you haven't really unless you can come back and describe exactly what you saw, and give some dimensions to it.
"So if you don't document what you're doing, you haven't done it."
While the caving craft was waning around the state, Graeme said there was an Australia wide network keeping it alive, with cavers travelling interstate to exchange ideas and techniques.
"We have a family of cavers- we pass the information along caver to caver, rather than family line."
Despite some older cavers finding their overalls getting a bit tighter, and their movement through the cave getting less swift, it was not squashing their passion for squeezing through tunnels.
"While I can still come underground I'll do it, and if I can find more, then that's a real thrill," said Graeme.
"There's nothing to worry about, all the hassles of everyday life disappear, you're just concentrating purely on what you're doing."