Resembling an overgrown garden, with tall blades of green grass replaced by white snow, penitentes are the coolest, sharpest snow formations around. It was once wrongly believed that this pointy Andes snowscape was carved out by the biting mountain wind.
Let’s get straight to the point – wind doesn’t create penitentes. These spikes of hardened snow develop where air is cold and dry, allowing the Sun to turn snow instantly into water vapour, without melting it first. This is called sublimation. Some areas sublimate quicker, leaving behind towering penitentes.
Sunlight turns snow into vapour, creating depressions, which catch more sunlight and so sublimate quicker. The high sides of the depressions become spikes.