Firn

Firn

Firn 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. It generally has a density greater than 550 kg/m³ and is often found underneath the snow that accumulates at the head of a glacier.

Snowflakes are compressed under the weight of the overlying snowpack. Individual crystals 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".

References

* [http://vulcan.wr.usgs.gov/Glossary/Glaciers/glacier_terminology.html USGS Glossary of Selected Glacier and Related Terminology]
* [http://www.physicalgeography.net/fundamentals/10ae.html Fundamentals of Physical Geography]


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  • Firn — del Glaciar Cascada del Sur, 80x aumento. Firn o nieve firn es una nieve parcialmente compactada, un tipo de nieve que ha quedado de inviernos pasados y se ha recristalizado hasta formar una substancia más densa que la nieve fresca. Es hielo que… …   Wikipedia Español

  • firn — s. (geogr.) neveu. Trimis de siveco, 05.08.2004. Sursa: Sinonime  firn s. n. Trimis de siveco, 10.08.2004. Sursa: Dicţionar ortografic  FIRN n. Zăpadă granulară compactă, formată în regiunile muntoase şi cele polare ca rezultat al compactizării …   Dicționar Român

  • Firn — * Firn, adj. et adv. welches nur im Oberdeutschen üblich, im Hochdeutschen aber unbekannt ist, vorjährig, von dem vorigen Jahre. Firne Früchte, welche im vorigen Jahre gebauet worden. Firner Wein. Im firnen (vorigen) Jahre. Von dem Firnen essen,… …   Grammatisch-kritisches Wörterbuch der Hochdeutschen Mundart

  • firn — s.m.inv. TS meteor., geogr. neve allo stato granulare | massa nevosa che forma il bacino di alimentazione dei ghiacciai {{line}} {{/line}} DATA: 1892. ETIMO: dal ted. Firn, da firn vecchio di (almeno) un anno …   Dizionario italiano

  • firn — consolidated snow, the raw material of glaciers, 1853, lit. last year s snow, névé, from Ger. Firn, from Swiss dial. firn of last year, from M.H.G. virne old, from O.H.G. firni, related to O.E. fyrn old, Goth. fairns of last year, from P.Gmc.… …   Etymology dictionary

  • firn — [firn] n. [Ger < firn, of last year, old, akin to OE fyrn, former < IE base * per , beyond > FAR, FIRST] the granular snow, not in a completely compacted mass, that accumulates at the top of a glacier …   English World dictionary

  • Firn — Sm (Firne f.) der vorjährige Schnee, Altschnee per. Wortschatz obd. (16. Jh.) Stammwort. Zu schwz. firn vorjährig . Sonst wird geschieden zwischen mhd. virne (*fernja ) alt und mhd. vern(e) u.ä. (*ferna ) vorjährig . Die jo Bildung auch in ahd.… …   Etymologisches Wörterbuch der deutschen sprache

  • firn — fȉrn m DEFINICIJA geogr. stari snijeg koji je postao zrnat i gust djelovanjem različitih procesa otapanja i smrzavanja, uključujući i sublimaciju, osnova je stvaranju ledenjaka ETIMOLOGIJA njem. Firn …   Hrvatski jezični portal

  • firn — firn; firn·ifi·ca·tion; …   English syllables

  • Firn — Firn, die körnige Schneemasse; daher Firne, die Spitzen der Alpen, welche mit ewigem Schnee bedeckt sind …   Pierer's Universal-Lexikon

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