Reference Work Entry

Encyclopedia of Snow, Ice and Glaciers

Part of the series Encyclopedia of Earth Sciences Series pp 290-293



  • Rachel W. ObbardAffiliated withThayer School of Engineering, Dartmouth College Email author 
  • , Ian BakerAffiliated withThayer School of Engineering, Dartmouth College
  • , Rachel W. LomonacoAffiliated withThayer School of Engineering, Dartmouth College


Crystal – A solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern such that regularly spaced atomic planes are found in three dimensions.

Firn – Compacted snow that has survived at least one melt season in a temperate glacier, or, in a Polar Region, compacted snow that underlies fresh snow, if any, and has undergone some metamorphism.

Firn-ice transition – The change from a packed granular material containing interconnected pores to a polycrystalline solid containing individual bubbles.

Grain – A small single piece of a substance. In firn, the term is used to refer to a single connected piece of ice, regardless of its atomic arrangement; hence, it could include one or more actual crystals. In polycrystalline ice, the terms crystal and grain are used interchangeably (Snow Grains).

Pore close-off depth – The depth at which only individual bubbles are found, rather than interconnected pores.

Snowpack – An area of naturally a ...

This is an excerpt from the content