Nieve penitente ice formations seen on Agua Negra Pass in the Coquimbo Region of the Andes, Chile

© Art Wolfe/Danita Delimon

A throng of ice and spires

If these frozen formations were named by more literal minds, we might know them as simply 'reverse icicles'. But the Andes, including this mountain pass rising above Chile's Atacama Desert, were mapped by poetically inclined Spanish explorers. They likened formations like these to countless kneeling figures reverently facing the sun, as a congregation of penitent parishioners kneeling at mass: hence the common name 'penitentes' for such packed-snow pinnacles.

Maybe the most dramatic penitentes appear in dry sections of the Andes, but they can form anywhere the sun beats down on snow enough to vaporise it faster than it can melt into water. Since snow isn't a perfectly even surface, some patches of the snowpack turn to vapour faster than others, creating pits that further reflect sunlight upon themselves. This speeds vaporisation within the pits, deepening them often all the way to bare earth, with unmelted portions of snow in between left standing (or kneeling) as penitentes.