A snowpack stratum differentiated from others by weather, metamorphism, or other processes.

Snow storms vary, with differences in wind, temperature and other factors, creating a layered snowpack.  With time, snow also settles and or changes, further differentiating the layers. As a result snowpack tends to be formed from a number of layers of varying hardness, strength, and cohesion. It is the relationship between each layer, that forms a basic element of avalanche forecasting.