From Wikipedia, the free encyclopedia
Jump to: navigation, search
Not to be confused with Fern.
Sampling the surface of a glacier. There is increasingly denser firn between surface snow and blue glacier ice.
Firn field on the top of Säuleck, Hohe Tauern

Firn (/fɪrn/; from Swiss German firn "last year's", cognate with before) is partially compacted névé, a type of snow that has been left over from past seasons and has been recrystallized into a substance denser than névé. It is ice that is at an intermediate stage between snow and glacial ice. Firn has the appearance of wet sugar, but has a hardness that makes it extremely resistant to shovelling. Its density generally ranges from 550 kg/m³-830 kg/m³, and it can often be found underneath the snow that accumulates at the head of a glacier.


In the summer months, the crystal metamorphosis can occur more rapidly because of water percolation between the crystals. By summer's end, the result is firn.
