The Marakoopa Caves at Mole Creek were formed by water, and in 2016 water again torrented through the cave system, hurling rocks, dumping gravel and carving paths.
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Looking up to the roof of the caves you can see rocks, some as large as a shoebox, stuck to the ceiling by calcite – evidence of previous floods that have filled the cavernous spaces.
In June 2016, 400 millimetres of rain fell on the Western Tiers, directly above the Mole Creek cave system, falling on two catchment systems that feed into the caves.
After extensive repair works the caves were once again opened for tourists, but how much had they changed?
The power of the water that coursed through the caves moved tonnes of gravel, boulders and destroyed infrastructure in the tourist attraction, which following the floods remained closed until December.
“There was a heavy influx of water into both of those catchments, what that did was obviously dislodge a lot of old alluvial gravels that must have been in the upper sections of the cave … and basically deposited it lower down in the caves,” senior cave guide Haydn Stedman said.
“About 80 tonnes worth of gravel became choke points which redirected the stream, which caused undermining of infrastructure like pathways et cetera, the electrical system was submerged and compromised, we had boulders [a metre across] bouncing around inside the cave, which is pretty awesome when you consider the power of water.”
But, Mr Stedman adds, this is not unusual in the history of the caves, which were formed by water dissolving the limestone rock they are made from, gradually opening up new caverns and spaces.
“You think of caves as something that don’t change over millennia, but there are certain events that cause quite a lot of changes,” Mr Stedman said.
“Of the significant areas of damage [in the 2016 floods] was an old sediment bank that we’ve had dated at about 40,000 years worth of sediment.”
Large dolerite stones and boulders are left behind as evidence of previous floods in the caves.
“Dolerite starts at nearly 500 metres above us, so that’s come down the mountainside, tumbled through the cave and somehow here it is,” Mr Stedman said.
Along with the destruction water can cause, there are also the secrets it can reveal.
“[After the flood] we found lots of interesting fossilised things in rocks as we were clearing,” Mr Stedman said.
“You’d clear out the dolerites and the sandstones, which have come from higher up, and you'd get to bits of limestone and every second rock we picked up, ‘Oh that’s interesting, there’s a cool fossil’.
“It dates back nearly 500 million years, so we had a paleontologist tell us that the oceans during the Ordovician [Period] were basically full of invertebrate fossils, so it’s the age of the trilobite, although unfortunately we don’t have those.”
Most of the fossils found were primitive sponge-like creatures, and some small shells.
In a wall just below the “cathedral” cave the fossils remain, like a tessellated pattern of textures and shapes.
When Mr Stedman returned to the caves following the 2016 floods, the enormity of the repair challenges ahead was immediately evident.
“We took, I think, three days to clear the doorway originally, we got into the cave because the force of the water had undermined and blown out a retaining wall that had been built there and we crawled in via a puddle,” he said.
“There was half a metre of gravel behind the door, and the door opened inward so there was no way you were going to force your way in.”
The electrical system needed to be entirely replaced, and the opportunity was taken to rethink and re-wire for a more user-friendly experience.
“Things have changed a lot in the last 40 years since the last incarnation of lights,” Mr Stedman said.
“[It was] set up for the interpretation of the time, which was more on the novelty aspect of the caves .. whereas our interpretation nowadays tends to be more abou the environment, the geology and how things react.”
More than $1 million was spent on the site, with 80 tonnes of gravel removed with shovel and wheelbarrow and hundreds of metres of lighting cable disappearing into the caves.
The caves are once again open as a key tourist draw to the area, attracting tens of thousands of visitors each year.
There is a long history of tourism to the caves, people used to visit in horse and buggy more than 100 years ago.
“There used to be major excursions as early as the late 1800s … it’s incredible when you think about how intrepid tourists were 100 years ago compared to today,” Mr Stedman said.
