GC: n

S: Humresp – https://www.humanitarianresponse.info/system/files/documents/files/MHB_Feb15_final.pdf (last access: 5 August 2015); NSDIC – https://nsidc.org/cryosphere/snow/science/avalanches.html (last access: 5 August 2015).

N: 1. 1763, from French avalanche (17c.), from Romansch (Swiss) avalantze “descent,” altered (by metathesis of -l- and -v-, probably influenced by Old French avaler “to descend, go down”) from Savoy dialect lavantse, from Provençal lavanca “avalanche,” perhaps from a pre-Latin Alpine language (the suffix -anca suggests Ligurian). As a verb, from 1872.
2. A mass of snow sliding, tumbling, or flowing down an inclined surface.
Technically, a mass of loosened snow, ice, and/or earth suddenly and swiftly sliding down a mountain. In practice, assumed to be a snow avalanche unless another term such as ice, rock, mud, etc. is used. (Avalanche-center.org) (ISDR).

S: 1. OED – http://www.etymonline.com/index.php?term=avalanche (last access: 5 August 2015). 2. RWP – http://www.who.int/hac/about/reliefweb-aug2008.pdf (last access: 5 August 2015) (p. 13).

SYN:
S:

CR: erosion, eruption, landslide, natural disaster, mudslide.