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Fox Glacier NZ
Blue ice occurs when snow falls on a glacier, is compressed, and becomes part of the glacier. Air bubbles are squeezed out and ice crystals enlarge, making the ice appear blue. Small amounts of regular ice appear to be white because of plenty of air bubbles inside them and also because small quantities of water appear to be colourless. In glaciers, the pressure causes the air bubbles to be squeezed out increasing the density of the created ice. Large quantities of water appear to be blue, as it absorbs other colours more efficiently than blue, and therefore a large piece of compressed ice, or a glacier, would appear blue. Original public domain image from Flickr
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