Sunlit Water

July 11, 2006

A Question My Sister Once Asked, For Which I Had No Answer

Filed under: Nature — by teofilo @ 12:08 am

Why are mountains purple?



  1. Silly, teo. It’s the same reason that we know that our “alabaster cities gleam / undimmed by human tears.”

    ‘Cause it says so right here.

    Comment by Stanley — July 11, 2006 @ 12:24 am |Reply

  2. I love that song. Strangely, I was unaware of the third verse.

    Comment by teofilo — July 11, 2006 @ 12:29 am |Reply

  3. Both my parents and my sister tell me that when I was a kid I used to have a joke that started “Why do trains run on tracks?” Apparently I would fall over laughing before I ever gave an answer. I have no memory of this, and consequently have no idea what my joke was.

    I think I asked the purple question too. There was no answer.

    Comment by eb — July 11, 2006 @ 1:45 am |Reply

  4. So does anyone have an answer? It’s a serious question.

    Comment by teofilo — July 11, 2006 @ 1:47 am |Reply

  5. I think it has to do with the same sunlight-passing-through-air/water phenomenom, that makes the sky blue and pretty sunsets/sunrises pink and red and orange and yellow.

    Beyond that, I’m useless. Sorry.

    Comment by Stanley — July 11, 2006 @ 2:12 am |Reply

  6. Some searching suggests it’s a reference to the way the Rockies look when the light and flora come together to produce a purple landscape.

    Comment by eb — July 11, 2006 @ 3:27 am |Reply

  7. this article says…”Purple mountains’ majesty: Another type of mirage can affect the way we see mountains, refracting light to make them appear larger. And that plays off our perception that bigger objects are closer than smaller objects. Once again, consult the Weather Doctor for an explanation of this “towering” phenomenon.

    There’s another type of mountain illusion, also having to do with atmospheric refraction. Water vapor in the air tends to scatter wavelengths toward the red side of the spectrum, which explains why the sky is blue. The light reflected from more distant objects has to travel through more of the haze — hence, they tend to appear bluer. As noted in this Encarta encyclopedia article, the scattering phenomenon is what makes mountains purple in the song “America the Beautiful.”

    If the atmosphere is particularly clear and dry, the light-scattering is reduced. As a result, distant objects are less blue, and we perceive them as closer.”

    Comment by catherine — July 11, 2006 @ 8:32 am |Reply

  8. Huh. That’s pretty similar to what I told my sister, except I was basically just making it up. The part about humidity is interesting; I’ll have to check it out next time I’m home. Thanks Catherine!

    Comment by teofilo — July 11, 2006 @ 3:50 pm |Reply

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