Helictites Disha Miglani   Recently, I made a recreational trip down to the Jenolan Caves (aka Binoomea, "dark places," by the Aboriginal population) in NSW Australia. Helictites are interesting limestone formations that defy the universal principle of gravity. They caught my interest when our tour guide explained that it is still not known how indeed, the unusual, twisted shaped, helictites form. There are three possible explanations. 1. The wind currents in the cave favour growth in a particular direction, by causing changes in the direction of dripping water. The problem with this theory is that there is no natural entrance into the cave, in which case there would have been no wind. Secondly, the wind changes direction very often, whilst the growth process is extremely slow, and the quick changes in air currents could not have caused all the various shapes. 2. The impurities deposited in the calcite and the minerals in the water have aphipathic properties, i.e they repel and attract each other and the water molecules, causing the various shapes in the limestone. 3. The Internal Hollow Straw Theory. This theory assumes that during the formation of the helictites, there was a thin central tube in which, water flowed as in straws. Capillary forces were then able to transport water ignoring gravity. During dry periods, the central channel became plugged, and when flow resumed, the pressure forced new channels out of the side of the original one. So, Do you have any ideas on how helictites form? If you do, please email us your possible theory, and the best responses will be posted on the website. Please limit your explanations to 100 words and email them to onset@unsw.edu.au by the 30th March 2005. The photos above were taken inside the Orient Cave.

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