A recent article in the local newspaper asks the question "Why does snow glow blue?"

The author gave one inspiration for the article as "..the way white snow glows turquoise in the holes left by boots or ski poles..."

The explanation given in the article is the same as that you can find elsewhere on the internet, and certainly applies to glacial ice: absorption of the red end of the solar spectrum upon passing through ice. Does it indeed apply to "holes left by boots or ski poles" in snow?

(The answer is "Not in fresh, light snow, though possible in more compressed or wetter snow." And for some quirk of this blog software, I cannot put the following plot in its proper location further down, so I place it here. Please ignore it for now and refer to it at the end of this post.)

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In 2012, I gave a "science cafe" talk with a local series sponsored by the Pacific Science Center, KCTS public television, and Science on Tap. The title was "The curious world of ice and snow". The location was a bar in Kirkland, but open to all ages. When I showed up with my family, they tried to seat us in the backup room, the regular room having filled up, but I said "Oh, well I'm the speaker" and they kindly created a space for my family in the regular room. I was indeed surprised at the crowd. People are apparently more interested in ice than I thought. (Hmm, but where are they when I post here?)

Click on any image to see an enlargement.

The basic structure of each talk was to give a lecture of about 30 minutes and then allow up to an hour (I think) for the Q&A. In my excitement, I had created 41 slides, in retrospect too many for the allotted time.

Given all the time spent preparing the slides, I hope that by posting them here that even more folks can enjoy the images and discussions. But, instead of unloading all of them on you at once, I will break the discussion into three sections. By adding the following table of contents, each section will have 14 new slides and the total will be 42, which according to Douglas Adams* is a really special number.


The contents of this section is part "1", written in green font.

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Last night I dreamed of a passage along a narrow river in a thick forest followed by a perilous descent down steep snow on a mountain.

And then this morning a friend sent me this picture.

Actually, I had asked him about the photo yesterday, so that explains my receiving it. I had asked because the lines in the picture had originally puzzled me. They appeared to be flow-lines, but this is a snowfield, not a glacier, and even if it was a glacier, the cause of the darkening wasn't obvious. But after talking about them with Steve Warren at the UW on Monday, I came to a simple conclusion. They are indeed flowlines of a sort, but it is not the ice that flowed. Rather, it is liquid water. That is, they are channels created by rainwater drainage.

Still, it doesn't detract from their beauty, does it?
And, in a weird way, it connects to my dream... as if my mind had assumed the form of a raindrop and fallen onto the snow.



--JN