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Monday, 1 January 2024

Melting firn, British Columbia

 


This image has appeared a lot on social media -- purporting to show a "melting ice patch" in the uplands of British Columbia.  It looks to me more like firn than ice, and it looks like a typical accumulation in a hollow where some nivation processes might have operated, but where the accumulation of snow annually has never been great enough to convert the mass into a small glacier.  So the firn field has been essentially static, and what we see are accumulation layers and annual surfaces created by irregular melting patterns in every successive summer season.  Anyway, because of the lack of movement, features under the lowest firn (or ice?) layers have remained undisturbed, and all sorts of interesting archaeological remains have been recovered from the newly exposed ground surface.  The oldest are over 6,000 years old, giving us a guide to the life history of the whole accumulation feature.

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