Called penitentes, these odd-shaped snow and ice structures form in high-altitude regions, such as the Chajnantor plain in Chile, due to the competition between sublimation (the change of snow and ice directly into water vapor) and melting. The resulting formations are shaped like thin blades, which are closely spaced and point in the direction of the sun.
At Chajnantor at the summer solstice, the sun is close to the zenith at noon, and penitentes are vertical. This image was taken in December 2005. [Image Gallery: Stunning Summer Solstice Photos]