Hi Bill again
Bill Payne wrote:
> On Mon, 15 Jan 2001 23:41:09 -0500 "Vandergraaf, Chuck"
> <vandergraaft@aecl.ca> writes:
>
> > Is it possible that the same principle caused the planes to sink deeper
> into the ice? I don't know if the pressure of the planes was sufficiently
> high to cause melting of the ice under the planes but there was lots of
> time.
>
> Hi Chuck,
>
> That's a great question.
>
> First, the post of David Bowman indicates otherwise: "One thing one
> might want to keep in mind here is the order of magnitude of the freezing
> point depression of water--which happens to be about only 0.0075 deg
> C/atm. This means that a local pressure in excess of 130 atm is
> necessary to depress the freezing point by only 1 deg C."
>
> As I'm sure you know, when water freezes it has enough force in expansion
> to crack the steel block of an engine (as my son-in-law almost discovered
> this winter). In order to reverse the process at sub-freezing
> temperatures, a confining force greater than the expansion force would be
> required to break the hexagonal structure of ice and cause it to melt.
>
True, but one fact we need to consider this that all glacial ice contains
air. At depths of less than 100 m air can be quite a significant fraction.
Dry snow is 99% air. Ice with a density of 0.6 is still 33% air. Even solid
glacier ice (0.9) contains tiny bubbles, although these are 1% or less, I
think. At low (<0.9) densities the ice is still somewhat granular and so will
behave differently to solid ice. Ice blocks are not a good analogy to use.
Something between granular old snow and partly refrozen crushed ice would be
better.
>
> But, perhaps ice remains somewhat plastic and is subject to "frozen
> flow." This would be a nice experiment to run in a lab to see if a
> weight with maybe 95% of 130 atm would deform solid ice with time and
> sink into the ice. If it did, then maybe the effect of the plane's
> weight in glacial ice over 50 years could be extrapolated.
>
> Another factor to consider is the density of the plane, assuming the
> plane remains filled with air. With the volume of empty fuel tanks and
> the airspace in the wings (outside of the fuel tanks) and the fuselage, I
> would think the plane would float in water. In fact, small planes "land
> " on water with only those little floats on the water, so the entire
> plane would have to be much lighter than water or ice. Therefore, the
> plane would tend to float in ice unless the ice filled up the air spaces.
This is an important point. These planes indeed have a low density.
However, until the reach great depths, their density would still be higher
than the firm and compacted snow. Also snow would infiltrate into the
interior of the planes fairly quickly, I would think, changing the overall
density. then there is the weight of overlying snow as well. I am inclined
to think that the snowshoe effect of the aircraft wings would be important
ins topping them sinking.
>
> I think Kent Hovind said he had talked to one of the men who had
> recovered the plane in 1992. I'll see if Kent can give me the name,
> maybe we could talk with him.
The web site I mentioned gives the accounts of the participants. However is
there was a consultant glaciologist with the party that could be useful. One
would want to know whether the ice that the aircraft rests on was on the
surface in 1942, or whether the aircraft have sunk down into older ice. If
the first is correct, explanations as to the high accretion rate would be
important. if the second, then by what mechanism. One web site had a link
to a technical report by Georgia tech. unfortunately this was defunct, so
whether it was a glaciological report or only an engineering study, I don't
know.
Respectfully
Jon
>
> Bill
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