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 再加几张banff trip的照片， 千年老冰，绿水如玉 |
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冰川上像水泥一样的叫Glacier Flour，也叫Rock Flour。当它们流入湖底形成沉积后，湖水往往会出现绿宝石 -- 偶而冒个泡 - (44 Byte) 2013-8-22 周四, 14:56 (713 reads) |
firefly
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作者：firefly 在 生活风情 发贴, 来自【海归网】 http://www.haiguinet.com
都是有些特定浓度的rock flour， 太多水太白，太少水就太蓝, 不多不少就蓝绿蓝绿的。
这次去看的lake louise，去之前大家都说好，又清又绿，可我去时水太白，掺牛奶似的，估计是rock flour太多。
有些海水也是蓝绿蓝绿的，我猜rock flour是海浪拍打岩石磨出来的，和冰川的grinding效果类似，而且浓度恰到好处。 直直的海岸线往往不怎么绿，估计海浪太急，易稀释，很难有大面积特定浓度的海水， 而海湾水流不急，容易出现大面积特定浓度的rock flour，也就容易出现蓝绿色， 我记得夏威夷好多海湾就这种蓝绿色。
lake tahoe 的emerald bay上面没有冰山吧？ 估计可能是湖水冲击岩石形成rock flour， 而且因为是湾， rock flour不易流走，r留在那里，浓度恰到好处。
yahoo有个解说不错:
Glacial lakes exist worldwide and some are green, some are blue. The reason is largely due to the fact that water absorbs different wavelengths of light. Depending on impurities and depth, different light spectrums are displayed. Deep lakes tend to be more blue because they absorb the weaker red spectrum. However, the rock flour can change what spectra are absorbed, thus a color shift occurs. Even living organisms such as algae affect the resultant color.
Actually glacial ice typically looks blue, not green. Assuming the ice is pure (it isn't), the reason it looks blue is because the normal spectrum of light from the sun is refracted within the ice. The red end of the color spectrum is a little less energetic and ends up being absorbed. The blue light is a bit more energetic and so the color shift is toward the blue end of the spectrum. Thus, it appears blue.
Adding various impurities affects the color greatly. Air bubbles can cause increased light reflection rendering the color whiter. Dirt (and rock flour, which is mostly tiny clay particles) again can have an effect on color, rendering the color grey or brownish, depending on the amount of the impurities. Once the sediment in a glacial lake settles to the bottom, the resulting color is again either blue (mostly) or green (next most likely).
To prove this to yourself, buy a large piece of block ice and place it in under a natural (fluorescent natural )or an OTT Lite (true daylight). I don't recommend putting the block in the sun simply because the sky is blue (due to the same principle of refraction and the same reason) and could effect what you see. Clean a surface so it is just pure, clear ice. Look inside. You will see a tiny shift toward the blue end of the light spectrum even in the block ice. Try some other light sources with varying color values. See what you get. If you are really interested, buy some color plastic films and use them as filters for your light sources.
Source(s):
I the early 70's my specialty was glacial geology and I was lucky to have the opportunity then and since to travel down into glacial crevasses and observe the effects first hand. Of course, I had to know the science beforehand, otherwise one looks and sounds like a dipshit among your colleagues. 
作者：firefly 在 生活风情 发贴, 来自【海归网】 http://www.haiguinet.com
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