The idea of acid dripping down through the soil, eating away at the very rocks under your feet tends to give you pause for thought as firm earth beneath you becomes pockmarked with caves and sinkholes.
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That this acid is dissolving the calcium filled bones and shells of tiny ancient animals doesn't make the picture any less disturbing!
A worrying thought at first, but it is reassuring to know that this process is simply rain reacting with carbon dioxide found naturally in the air and soil.
This forms a very weak acid called carbonic acid.
This is the same substance that makes fizzy drinks taste tangy.
The ever so slightly acidic rain drips down through the soil dissolving the bedrock limestone that was deposited sometime in the middle Cambrian period, perhaps around 500 million years ago, when seas covered most of our planet.
The sea was chock full of small molluscs, snails and trilobites. As these critters died, their bones and shells settled on the sea floor.
There they were squashed by the weight of generations of slithery and shelled critters to eventually become limestone formations like the fossil rich Tindal limestone common around Katherine.
The weak carbonic acid rainfall erodes the limestone and as the acid solution drains away through the cracks and crevices in rock and soil it leaves cavities that become ever bigger over time and eventually a cave is formed.
The caves at Cutta Cutta Caves Nature Reserve have been formed by this slow erosion of rock. Beautiful formations seem to drip from the ceiling and flow down the walls of the cave.
These grow slowly, each season's rainfall adding a thin layer of calcium crystal.
The thickness of the layers is influenced by the amount of rain falling and with that they are a wonderful record of climate change over time.
Late dry season fires and land clearing allows the heavy rains of the wet season to erode soil much more quickly from these areas than if there was a good coverage of trees and dry grass.
The soil that is eroded from bare areas is taken down through sinkholes and cracks in the earth and can silt up the caves, filling them with mud.
We limit the siltation of the caves at Cutta Cutta Caves Nature Reserve when we manage late season fires and limit the disturbance of vegetation.
The caves at Cutta are open daily with guided tours of the cave.
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