Why the Nullarbor Caves are Unique
Text and image by Professor Jon Woodhead There are many caves in the world and so it is reasonable to ask what makes the Nullarbor so special? We know that caves have been forming on Earth since at least the Devonian Period some 400 million years ago when land plants first evolved (the decomposition of plant matter in soils forms dilute acids which promote limestone dissolution) but it is extremely rare for them to be preserved. The reason is that the other ingredient required to form caves is water and, unfortunately, the natural geological processes of erosion and weathering in wet environments, acting over many Millenia, eventually destroyed most of these early cave systems. The Nullarbor Plain is an ancient seabed, which probably first emerged from the sea around 14 million years ago driven by tectonic forces acting on Australia’s southern margin. We now know from radiometric dating of cave deposits that the Nullarbor caves started to form around 10 million years ago with a peak in development around 3 to 6 million years ago when the entire planet was a much wetter place. But then something extraordinary happened – much of the Australian continent relatively quickly became arid, effectively shutting down the water-driven erosional processes that have destroyed ancient caves elsewhere and leading to the remarkable preservation of the Nullarbor caves. As far as we know this fortunate confluence of events has not occurred on such a scale anywhere else on Earth. On the Nullarbor you can walk into many caves full of pristine stalagmites and marvel at the fact that every one of them formed many millions of years ago – something that is not possible anywhere else on our ancient planet. These are unique worlds with many remarkable stories to tell. Yet, as very shallow caves, they remain fragile to human disturbance. As such the Nullarbor is a highly inappropriate venue for an industrial development of any form.