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Firn (; from

Swiss German Swiss German (Standard German: , gsw, Schwiizerdütsch, Schwyzerdütsch, Schwiizertüütsch, Schwizertitsch Mundart,Because of the many different dialects, and because there is no defined orthography for any of them, many different spelling ...

"last year's", cognate with ''before'') is partially compacted

névé Névé is a young, granular type of snow which has been partially melted, refrozen and compacted, yet precedes the form of ice. This type of snow is associated with glacier formation through the process of ''nivation''. Névé that survives a ...

, a type of

snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughou ...

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 0.35 g/cm³ to 0.9 g/cm³, and it can often be found underneath the snow that accumulates at the head of a

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such a ...

Snowflake A snowflake is a single ice crystal that has achieved a sufficient size, and may have amalgamated with others, which falls through the Earth's atmosphere as snow.Knight, C.; Knight, N. (1973). Snow crystals. Scientific American, vol. 228, no. ...

s are compressed under the weight of the overlying

snowpack Snowpack forms from layers of snow that accumulate in geographic regions and high elevations where the climate includes cold weather for extended periods during the year. Snowpacks are an important water resource that feed streams and rivers as t ...

. Individual

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

s near the melting point are semiliquid and slick, allowing them to glide along other crystal planes and to fill in the spaces between them, increasing the ice's density. Where the crystals touch they bond together, squeezing the air between them to the surface or into bubbles. 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. The minimum altitude that firn accumulates on a glacier is called the ''firn limit'', ''firn line'' or ''snowline''.

List of firns

* Antarctic Firn *

Daniel Bruun Firn Daniel is a masculine given name and a surname of Hebrew origin. It means "God is my judge"Hanks, Hardcastle and Hodges, ''Oxford Dictionary of First Names'', Oxford University Press, 2nd edition, , p. 68. (cf. Gabriel—"God is my strength ...

* Dreyer Firn *

East Northwall Firn The East Northwall Firn was a glacier on Mount Carstensz in the Sudirman Range on the island of New Guinea in Central Papua province, Indonesia. Situated at an elevation of approximately NNW of Puncak Jaya, the highest summit in Oceania. It bro ...

* Rink Firn * Sven Hedin Firn''Sven Hedin Firn'',

Army Map Service The Army Map Service (AMS) was the military cartographic agency of the United States Department of Defense from 1941 to 1968, subordinated to the United States Army Corps of Engineers. On September 1, 1968, the AMS was redesignated the U.S. Army ...

United States Army Corps of Engineers , colors = , anniversaries = 16 June (Organization Day) , battles = , battles_label = Wars , website = , commander1 = ...

, Greenland 1:250,000 *

West Northwall Firn The West Northwall Firn was a glacial body on Mount Carstensz in the Sudirman Range on the island of New Guinea in Central Papua province, Indonesia. The glacier was situated at an elevation of approximately to , centered a little over northwest ...

Other uses

In colloquial and technical language, 'firn' is used to describe certain forms of old snow or harsch: * Old snowfields or

(''Firnfelder''), even if the snow is not yet one year old * the more recent snow layers of a glacier (a 'firned' glacier) * the uppermost, soft layer of snow that is frozen overnight and, as a result of spring sunshine and high air temperatures, forms on an area of old snow or '' harsch'' (a slope ''firns up''; in Switzerland called ''Sulz'', but this term in Germany refers to a certain depth at which skiing downhill is no longer enjoyable)

References

Sources

* * * * {{Ice Glaciology Water ice Montane ecology Mountaineering Snow