Geochronology/Ice cores/Firns

Firn is granular snow, especially on the upper part of a glacier, where it has not yet been compressed into ice.

In a snow pit, snow layers are composed of progressively denser firn. Credit: USGS.

Theoretical firn


Def. "a type of old snow which has gone through multiple thaw and refreeze cycles and thus is made of numerous small icy grains, though it is not nearly as saturated with water as snow-cone slush is; can be hard or somewhat soft depending on recent and current weather conditions"[1] is called firn.

Def. "rounded, well-bonded snow that is older than one year; firn has a density greater than 550 kilograms per cubic-meter (35 pounds per cubic-foot); called névé during the first year"[2] is called firn.


  1. MartianBachelor (26 August 2006). "firn, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2014-09-17. {{cite web}}: |author= has generic name (help)
  2. Jane Beitler (2014). "Cryosphere Glossary". National Snow and Ice Data Center. Retrieved 2014-09-18.

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