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Penitent SnowIf you want the beauty of winter without having to brave the bone-chilling temperatures blasting much of the United States this week, snuggle into a soft blanket, grab a warm beverage, and curl up with some of these natural frozen wonders. Nieve penitente, or penitent snow, are collections of spires that resemble robed monks—or penitents. They are flattened columns of snow wider at the base than at the tip and can range in height from 3 to 20 feet (1 to 6 meters). The picture above shows the phenomenon in central Chile. (See pictures of the patterns in snow and ice.) Nieve penitente tend to form in shallow valleys where the snow is deep and the sun doesn't shine at too steep an angle, said Kenneth Libbrecht, a physicist at the California Institute of Technology in Pasadena who studies ice crystal formation. As the snow melts, dirt gets mixed in with the runoff and collects in little pools here and there, he said. Since the dirt is darker in color than the surrounding snow, the dirty areas melt faster "and you end up digging these pits," explained Libbrecht. "They tend to form at high altitude," he said. But other than that, no one really knows the exact conditions that are needed to form penitent snow. "They're fairly strong," Libbrecht said. "People have found [the spires] difficult to hike through." —Jane J. Lee

Photograph by Art Wolfe, Getty Images