I thought glaciers were made of snow, so why do glaciers sometimes look blue and not white?

Asked by Frank

When snow falls on glaciers, it forms layers. Older snow becomes compressed by the weight of new snow on top of it. This is called firn. Gradually, more and more snow falls on top of this firn, compressing it further. This eventually becomes glacier ice. The crystal is changed, and glacier ice is typically crystal clear. The refractive properties of this crystal makes it appear blue.

About

I am a Senior Lecturer at Newcastle Univeristy, specialising in glaciology and glacial geology. I wrote and developed the AntarcticGlaciers.org website as part of an ongoing commitment to outreach, education and research impact. Read more about me at www.antarcticglaciers.org/bethan-davies.

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