Physical phenomena of blue ice caveYuecheng HeAward: Top 100
School: chengdu foreign languages school, xinjin This photo was taken in Hofn i Hornafiroi, Iceland, during my winter vacation trip. Why are the ice in Blue ice caves blue? The reason why they appear blue is that they absorb most of the spectrum of sunlight, especially the red wavelengths, and reflect the blue wavelengths more efficiently. The ice in a glacier is dense and thick, which makes it easier to absorb longer wavelengths of light, such as red, while shorter wavelengths, such as blue, are reflected back. In addition, tiny bubbles trapped in the ice disperse incoming light, enhancing the visual effect of glacial blue. So when we look at a glacier, what we mostly see is the reflected blue light that gives the glacier its amazing blue appearance. This distinctive blue color is one of the characteristics of the glacier as a natural wonder. But regular ice doesn't look like this. There are two reasons for this. First, normal ice freezes for a short period of time so that it doesn't have as many bubbles. The second reason is size. Regular ice is so small that only a little red light is absorbed by it. 
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