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Dry quicksand is loosesand whosebulk density is reduced by blowing air through it and which yields easily to weight or pressure. It acts similarly to normalquicksand, but it does not contain any water and does not operate on the same principle. Dry quicksand can also be a resulting phenomenon of contractivedilatancy.
Historically, the existence of dry quicksand was doubted, and the reports of humans and complete caravans being lost in dry quicksand were considered to befolklore. In 2004, it was created in the laboratory,[1] but it is still not clear what its actual prevalence in nature is.
Writing inNature,physicistDetlef Lohse and coworkers ofUniversity of Twente inEnschede,Netherlands allowedair to flow through very finesand (typical grain diameter was about 40micrometers) in a container with a perforated base. They then turned the air stream off before the start of the experiment and allowed the sand to settle: thepacking fraction of this sand was only 41% (compared to 55–60% for untreated sand).[1]
Lohse found that a weightedtable tennis ball (radius 2 cm, mass 133 g), when released from just above the surface of the sand, would sink to about five diameters. Lohse also observed a "straight jet of sand [shooting] violently into the air after about 100 ms". Objects are known to make asplash when they hit sand, but this type of jet had never been described before.
Lohse concluded that:
During the planning of theProject Apollo Moon missions, dry quicksand on the Moon was considered as a potential danger to the missions. The successful landings of the unmannedSurveyor probes a few years earlier and their observations of a solid, rocky surface largely discounted this possibility, however. The large plates at the end of legs of theApollo Lunar Module were designed to reduce this danger, but theastronauts did not encounter dry quicksand.
