Blue ice
My parents took me every where as a kid. And so it's likely I have actually seen a glacier. In fact, knowing them, we probably camped out on one once, roasted marshmallows, sang songs and I can't even remember it. So the travel channel has an annoying show on (that I've only watched once) where they take a lucky couple around the world on an all-expense paid trip to 1000 places to go before you die . Since I'm extremely jealous, I'll criticize it. While the lucky couple were visiting Spencer glacier in Alaska, the topic of the very blue ice came up, which the voice-over awkwardly and incorrectly explained was due to the ice absorbing blue light. Awkwardly, to the point that it was clear some one had once told them the correct explanation and then they bungled it when writing the script. So, FWIW here's my two cents. It's two effects. First, when white light enters the ice, sources claim that red and green are more strongly absorbed by ice than blue, although I have not been successful in locating a visible spectrum of ice (reason for delay of this post). But this is reasonable so I'll parrot it back. So inside of the ice, reds and greens are starting to get absorbed, so you have a bias for blue light. By itself this is not enough - after all, how does the blue light get back out so that we can see it? This is the second part, which is a process called scattering. Light scatters in a medium randomly in all directions so that some of this blue light makes it out. Also, the scattering is likely to greatly increase the path length of the light in the ice since it will keep light bouncing around in the ice longer, ensuring more absorption of the longer wavelengths (reds, etc). A further wrinkle on this which is probably also important is that scattering favors blue light slightly, so that reds are less likely to escape out and instead will be more likely to pass through the ice and terminate on an absorptive surface (dust, dirt, rock, whatever...). These combined effects add up to give a very brilliant blue that I would love to see in person one day. I invite the travel channel to give me a free ride.