Perhaps this is naïve of me, but I always thought mound springs were small. Thinking of things like sand, gravel, and other rocks, my personal experience of things called ‘mound’ were that they generally stood less than 2 m tall. Therefore, in my mind, a mound spring would also stand 1-2 m tall. I discovered recently that some mound springs are huge. I’ve met topographical features named ‘mount’ that were smaller (although, if we’re honest, there’s many a ‘hill’ or ‘small rise’ that’s been given the name ‘mount’ in Australia; Mount Young comes to mind).
We visited The Bubbler (Pirdali-nha) and Blanche Cup (Thirrka) on the way to Alice Springs from Adelaide. The Bubbler is a fascinating water hole – it is a shield shaped mound approximately 4 meters high. It is approximately 70 meters across at the top and 350 meters wide at ground level. Probably the most interesting feature is that it has bubbles of gas escaping from under the sediments inside. I’m not sure what the gas actually is – I’ve been told both carbon dioxide and radon gas… it could be a mixture of the two. A quick traipse through the literature didn’t give any further information so there’s nothing more I can say on that.