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RE: Quicksand



--- Ken.Carpenter@dmns.org wrote:

> Sorry, but the Tarzan quicksand actually is a mixture of shredded
> cork
> in a small pond (watch closely next time). True quicksand requires
> water
> to be pushing upwards at a small spot (called dewatering) in order to
> keep the sand grains buoyant. 
    This is well-known - you can also get it with lateral travel of
water (my tidal pool trapped behind a sand bar exposed by falling
tide). But I can also envisage appropriate circumstances of you have
inter-bedded sands and clays with dry sub-aerial sand, a clay bed and
below a bed of wet sand. Given suitable local conditions of pressure
(head, tilting, artesian conditions) it's then not implausible to get
an upwelling with "predator trap" potential. (I realised where that
phrase stuck into my head earlier - I'd got an on-disc copy of a BBC
Horizon program with Phil Currie talking about his multi-tyrannosaurid
site (Albertosaurus?), and having to reject a predator trap as an
explanation for the specimen's association). Still, quicksand isn't
particularly sticky, and the density should be sufficient to make most
land animals buoyant enough to survive ... if they don't panic. Being
buoyant is neither necessary nor sufficient to prevent drowning.
    Thinking more about dodgy ground conditions, ISTR that a
sand-clay-sand stratigraphy has been blamed for things like the
undermining of the Leaning Tower of Pisa at the very least, and I'd not
be surprised to learn that the annals of civil engineering are full of
other examples in deltaic settings (or would be if they hadn't been
found long since in most long-settled areas).

> There is no such thing as dry
> "quicksand"
> either because the sand grains are too heavy to be buoyed by air.
    Hmmm. "Singing sands". Hmmm. I'd be careful about being /too/
absolutist. Bloody sediments - why can't they just get buried to 100km
and get properly equilibrated. (As my met.pet. lecturer used to say.)

> Movies
> are full of hokey things 
    Slice of rubber crocodile, any one?

> And no "Whatever took Romeo and Juliette down had to have been pretty
> much instant." Read my pdf describing the specimens:
>
https://scientists.dmns.org/sites/kencarpenter/PDFs%20of%20publications/
> theropod%20predation.pdf
    I did. Interesting. I feel a visit to the Inter Library loan
service when I get onshore and paying a couple of hour's wages for some
of the Palaeo.Polonica papers.
    Never having been on any sort of a dino digging task, I would guess
that once you've found a nice specimen, someone goes up and down dip
and along strike to do a couple of sedimentological logs of the
context, while others are getting physical with the sledgehammer and
toothbrush? Or is that the difference between theory and practice?


-- 
Aidan Karley,
Aberdeen,
Scotland


                
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