lower line of an area (such as a mountain) covered with snow for most or all of the year; latitudinal line indicating where snowfall begins at sea level
The lowest elevation area of a perennial snow field on high terrain, such as a mountain range
Altitudinal or latitudinal limit separating zones where snow does not melt during the summer season from areas in which it does Similar to the concept of firm limit except that it is not limited to glaciers