WHEN all other forms of inspiration failed, the scriptwriters of black and white movies of the 1950s had a satisfying way of ridding themselves of any villain superfluous to the plot: he would fall into a pit of quicksand, and could be observed getting his just deserts, struggling wildly as he was sucked inexorably into its depths. Naturally the hero tried to save him - but usually failed. The last we would see of the bearded rascal was an upstretched hand, vainly gesticulating for help before it, too, finally disappeared below the surface of the quagmire.
The perceived evil nature of quicksand is emphasised by its very name. It derives from an archaic form of the word
"quick", which meant to "be alive", or "moving", and which seems to impute an active malevolence to the sand itself. But in fact, if you just add water, any sand is quicksand, and what is more, it does not suck its victim downwards, but will try to support him given half a chance.
Sand is most familiar to use in the guise in which we see it on the sea shore - either dry and powdery, or hard packed, damp and firm. Since the grains of which it is composed are irregular in shape and, rough, they lock together to support the weight of anything upon them. Sand becomes, "quick", however, when water, usually up welling from a subterranean source, surrounds the individual grains, and fills the little gaps and spaces in between; then they cannot lock together, the sand behaves like liquid, and the only weight it can support is that determined by the familiar Archimedes Principle.
Quicksand, therefore, is most likely to be found where there are springs, where water falling on relatively high ground is carried downward through channels in the rock to surge upwards again at some lower level underneath an area of sand. It follows that quicksand is rarely found on flat countryside, or where the landscape has deep ravines and gorges into which the water drains. It is a phenomenon of a moderately hilly landscape of the kind where springs are common.
The secret of survival for the villain in the quicksand is "Don't panic!" The mixture has a density of 1.6 or thereabouts, compared to 1.0 in the case of fresh water, and 1.02 for salt water, so anyone lying calmly on their back with arms outstretched will be supported even more effectively than if floating on the surface of the sea. The difficulty, if you go in feet first, is that quicksand has a reluctance to "let go"; to extract a limb, you have to fight hard against the vacuum left behind.