When looking a Glaciers for the first time 'in the flesh' the range of colours - from deep blue to white - is astounding. But to understand why you need to turn to science. When snow falls on a glacier, an becomes compressed over time the are bubbles are squeezed out. And the ice crystals become enlarged. This is what makes the ice appear blue. As they break off the glacier face, they become exposed to air, and overtime the surface becomes lighter in colour - eventually begin white like snow.