It?s often said that all stalactites start life as straw stals ? and, indeed, it is a matter of observation of broken stals that they generally (always?) have a tiny hole running roughly down their centre. Then, so the argument goes, water laden with calcium bicarbonate starts to run down the outside of some stals, where calcite is deposited, to give the typically pointed stalactites that we see. But how does this putative process work in practice?
If water somehow seeps out of a hole at the top of a straw (because a blockage develops lower down?) one would expect it to do so on one side only, hence one might expect bigger stalactites to be asymmetrical, rather than the quasi-symmetrical ones we see in practice. I guess that for a small-diameter straw the influence of something such as capillary forces may tend to cause it to run all the way round the top of the straw and hence slowly run down the outside in a symmetrical fashion ? but I wouldn?t expect this to happen once this process of building up CaCO3 on the outside has proceeded to any great extent.
So how do tapered stalactites form in a quasi-symmetrical fashion?
If water somehow seeps out of a hole at the top of a straw (because a blockage develops lower down?) one would expect it to do so on one side only, hence one might expect bigger stalactites to be asymmetrical, rather than the quasi-symmetrical ones we see in practice. I guess that for a small-diameter straw the influence of something such as capillary forces may tend to cause it to run all the way round the top of the straw and hence slowly run down the outside in a symmetrical fashion ? but I wouldn?t expect this to happen once this process of building up CaCO3 on the outside has proceeded to any great extent.
So how do tapered stalactites form in a quasi-symmetrical fashion?