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Melting under pressure, was Squeeky Snow.



The "melting under pressure" idea was discussed here several
winters ago. It was pointed out that pressure must be very
high to produce melting. I do not think that pressures
generated by shoes are sufficiently large.

At that time I conducted a classical experiment in which a
loaded wire was penetrating a block of ice. It worked as
described in textbooks at room temperature but not on the
porch where the temperature was below freezing. The
conclusion was that "caloric traveling along the wire melts
the glass, not the pressure".

Feel free to replace the quoted phrase with "more correct"
wording. Your formulation will probably be much longer
than mine and not necessarily more clear.
Ludwik Kowalski

"Dwight K. Souder" wrote:

I'm just thinking out loud. Living in Ohio, we are not subjected to such
extreme cold temperatures. Several years back, I noticed this squeeky snow and
that was a time when temperatures were so cold that people's nylon coats were
becoming brittle and cracking. Also, the paints on cars were peeling off from the
extreme cold. I also remembered the snow did not pack into snow balls very easily
(I was in college and snow ball fights were known to break-out from time to time.
:) ). When it is warmer, the snow does pack very well.
My thinking is that the squeekiness is similar to what happens if you place
several glass marbles in your hand, squeeze them, and roll them around. I'm think
that a similar thing is taking place at a much smaller scale. The extreme cold
keeps the snow from partially melting when pressure is exerted on it, but the snow
particles are still sliding past oneanother.
During warmer temperatures, the snow is able to partially melt and stick
together when pressure is exerted on it. The transfer and change of pressure on
the snow causes small cracking to occur which then causes the crunchy snow.
Like I said, I'm just thinking out loud. So I may be way off on some of my
thoughts.

Out making snow-angels,
Dwight
Ashland, OH