Mica schist. Credit: U.S. National Parks Service.
Snow is precipitation consisting of flakes or clumps of ice crystals. The crystals are plane hexagonal, showing an infinite variety of beautiful branched forms; needles, columns, and irregular forms are also found. Snow forms by direct vapor-to-ice condensation from humid air below 0°C. On reaching the ground, snow crystals loset their structure and become granular. Fresh snow is very light (specific gravity about 0.1), and is a good insulator, protecting underlying plants from severe cold. In time, pressure, sublimation and melting and refreezing lead to compaction into névé.
It is often said that no two snowflakes are alike. While this is hard to prove, individual samples can be captured on a chilled glass microscope slide and preserved with artist's spray fixative. All are six-sided and the more ornate kind, called dendritic snowflakes, form when the air temperature is between -12°C to -16°C (10°F and 3°F). Typical snowflakes fall at a rate of a meter or two per second; assuming 1.5 meters per second and a cloud base of 3,000 meters (roughly the height of nimbostratus clouds) gives a descent time of 20 minutes.
Words for snow
One of the great urban legends is that the Inuit have n words for "snow," where n is a large number. This story may have started in 1911 when anthropologist Franz Boaz casually mentioned that the Inuit – he called them "Eskimos," using the derogatory term of a tribe to the south of them for eaters of raw meat – had four different words for snow. With each succeeding reference in textbooks and the popular press the number grew to as many as 400 words. A problem with trying to pin down exactly how many Inuit words there are for snow and/or ice, or for anything else, is that the various dialects of Inuit are polysynthetic, which means that words can effectively be made up on the spot by concatenating various particles to the root word. For example, the suffix -tluk, for "bad," might be added to kaniktshaq, for "snow," to give kaniktshartluk, "bad snow." This can give rise to any number of snow terms, from akelrorak ("newly drifting snow") to mitailak ("soft snow over an opening in an ice floe").
Snowblindness is temporary loss of vision with severe pain, tears, and edema due to excessive ultraviolet light reflected from snow. Permanent damage is rare but protective Polaroid glasses should be used.
A snowmobile, or motor sled, is a motorized vehicle with two skis in front and propelled by an endless track, used for traveling over deep snow. First developed in the 1920s to replace dogsleds, they have become popular for recreation and racing since lightweight models were introduced (1959).
A snowshoe is a broad, light footwear (about 1m × 0.4m) consisting of a wooden frame, laced with leather, strapped to the shod foot. Spreading the wearer's weight over a large area, they enable him to walk on deep, soft snow. Snowshoe racing is a popular sport, speeds of about 1 kilometers in 3 minutess being attainable.