The invalidity of extrapolating from the top 200 feet to the bottom should be emphasized, as glacial ice is greatly compacted relative to the surficial layers.
Another factor that must be considered is the configuraiton of the plane relative to local ice flow patterns. Was the overlying ice entiraly the result of subsequent accumulation?
Dr. David Campbell
"Old Seashells"
Biology Department
Saint Mary's College of Maryland
18952 E. Fisher Road
St. Mary's City, MD 20686-3001 USA
dcampbell@osprey.smcm.edu, 301 862-0372 Fax: 301 862-0996
"Mollusks murmured 'Morning!'. And salmon chanted 'Evening!'."-Frank Muir, Oh My Word!
---------- Original Message ----------------------------------
From: David_Bowman@georgetowncollege.edu
Date: Mon, 15 Jan 2001 09:41:17 -0500
>Regarding:
>>>> The WW II airplane was found beneath, I think, more than two hundred feet
>>>> of ice. I would think the large surface area of the plane's wings would
>>>> have prevented it from exerting enough pressure on the ice to melt its
>>>> way down through the ice. Assuming that's true, then the ice accumulated
>>>> over the plane since it went down.
>>> ...
>> If the possibility of the plane melting its way through the ice or snow
> is
>>at issue, what would be important would not be just relative densities (as if t
>he
>>issue were simply buoyancy) but whether or not the plane would exert sufficient
>>pressure to depress the freezing point enough to liquify the ice.
>>That would depend on the plane's mass distribution & the surrounding
>>temperatures. But doing the calculation is perhaps overkill since, as you note
>,
>>this YEC argument is one of desperation.
>
>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. An even lower
>freezing point requires a correspondingly proportionate pressure increase.
>Even with the realization that snow is mostly air pockets rather than
>solid ice, and even with the realization that various sharp parts on the
>underside of the plane would initially locally exert much greater
>pressures than other parts, I suspect that any significant melting that
>would occur because of the introduction of the airplane into the
>environment would be nearly completely a result of the released energy
>upon impact from the energy of the crash itself, and and maybe from any
>burning fuel. It seems to me that the *crash* of the airplane would be
>sufficiently energetic for at least parts of the plane to be relatively
>deeply burrowed into a preexistent field of snow.
>
>Another thing to keep in mind is that it takes a lot of initial surface
>snow to eventually wind up much later as a thin deep pack ice layer.
>
>Another thing to bear in mind is that the ice accumulation proccess
>that would happen around an inhomogeneous obstruction like an airplane
>would be expected to be modified to a large degree by the plane's
>presence compared to the accumulation process out in more open spaces.
>
>Any calculation of the depth of burial relative to the time since the
>plane crash would need to at least account for some of these other
>processes that would be expected to swamp any static pressure-induced
>freezing point depression effect. In any event, I agree with George's
>assessment that "doing the calculation is perhaps overkill since, ...
>this YEC argument is one of desperation".
>
>David Bowman
>David_Bowman@georgetowncollege.edu
>
>
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