SNOW LINE

(1) The general altitude to which the continuous snow cover of high mountains retreats in summer, such as the Snowcap of a mountain, chiefly controlled by the depth of the winter snowfall and by the summer temperature. (2) A line, sometimes drawn on a map during the winter, which shows the lower elevation of the snow cover at a particular time. (3) The fluctuating latitudinal boundaries around the polar regions marking the extent of snow cover.