Depth hoar are large crystals occurring at the base of a snowpack that form from when uprising water vapor freezes onto existing snow crystals. Depth hoar crystals are large, sparkly grains with facets that can be cup-shaped and that are up to 10 mm in diameter. Depth hoar crystals bond poorly to each, increasing the risk for avalanches.
The formation of depth hoar in artic or antarctic firn can cause isotopic changes in the accumulating ice. This can influence analysis of ice cores in scientific research