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Glacier Color



Hi, folks,

This discussion on sky color has been interesting and informative.
I have a similar question whose answer I thought I knew, but now
have some doubt about.

This summer I traveled to Alaska where I was able to land by
helicopter on the surface of a glacier. I had seen the faces of glaciers
by ship and observed the blue color of the face, but on the top the color
of the ice in shallow crevasses was spectacular. It almost seemed as
though a can of blue paint had been poured into the crevasse. These
crevasses were not deep, in most cases being no more than five or six
meters.

Now, the standard explanation I have read for the blue color holds that
the intense pressure due to the weight of the glacier somehow changes the
crytalline structure of the ice. Another explanation claims that glacier
ice
is no different from ordinary ice - there's just more of it. Yet even on
the
surface (where, presumably, the pressure is small) the blue color is intense
and even small pieces of ice are blue. I saw an iceberg that had melted
away
until a very thin sheet jutted up out of the water. Even though it was
almost
transparent, it was also blue.

I would appreciate it if anyone could help me out here. If the answer
is
(a), how does compacting the molecules change the color???

Thanks,
Wes Davis