Penitentes

Penitentes, or nieves penitentes (Spanish for “penitent snows”), are snow formations found at high altitudes. They take the form of elongated, thin blades of hardened snow or ice, closely spaced and pointing towards the general direction of the sun. As the sun hits the snow, it transforms it directly into vapor without melting it, through a process called sublimation. The ice vaporizes without turning into a liquid first. Initially smooth, the snow surface thus develops depressions, hills, and hollows as some regions sublimate faster than others. As the carved surfaces then continue to concentrate the sunlight, they help to speed up the process. This results in icy snow columns that look like towering spikes.