Almost all glacier travelers have stared with awe into the brilliant blue depths of an open crevasse. The bright white snow of the surface is a marked contrast to the deep rich blue inside a glacier. But why is ice blue?

Snow is white because full spectrum, or white, light is scattered and reflected at the boundary between ice and air. The white color of bubbles at the top of a dark beer work the same way—small pockets of air reflect and scatter visible light. Ice only appears blue when it is sufficiently consolidated that bubbles do not interfere with the passage of light. Without the scattering effect of air bubbles, light can penetrate ice undisturbed. In ice, the absorption of light at the red end of the spectrum is six times greater than at the blue end. Thus the deeper light energy travels, the more photons from the red end of the spectrum it loses along the way. Two meters into the glacier, most of the reds are dead. A lack of reflected red wavelengths produces the color blue in the human eye.



intro | terminology | accumulation | firn | blue | ablation | water | equilibrium | massbalance | movement | crevasse | structure | algae | moraine | debris | erosion
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Benjamin Drummond 2002