A horizontal unit in the snowpack that shares relatively similar characteristics.

Credit: Crested Butte Avalanche Center

The snowpack is stratified – or made up of layers upon layers stacked on each other. Similar to the geologic layers in the Grand Canyon, the snowpack stratigraphy tells the history of the season’s snowpack. Snow layers initially form due to distinct weather episodes such as snowstorms, wind events, warm-ups, and dry spells. They then further evolve within the snowpack. In a snowpit, you can identify and classify layers based on distinct changes in hardness, grain size, grain shape, and density. 

Layers of a snowpack. Credit: Sawtooth Avalanche Center

Multiple stacked layers of wind drifted snow contributed to this slab avalanche. Credit: Crested Butte Avalanche Center