A free climber begins her winter ascent of Big Bend National Park’s Burro Mesa Pour-Off, a desert waterfall that is only active after substantial rains. She made it into the cave, but the slick, volcanic rhyolite at the higher levels of the pour-off made it impossible to continue. Photo taken January 14, 2013 with a Nikon D7000 and 18-55mm f3.5-5.6G Nikkor lens. Entered in the 2013 National Geographic Traveler Contest. Click photo to enlarge.