Colorado's giant sponge

Where did you go? Great Sand Dunes National Park in Colorado, home to the largest dunes in North America.

What did you do? Climbed the 710-foot "High Dune." The hike is a Soviet shuffle – two steps forward, one step sliding back. Socks are the footwear of choice because boots fill in seconds and bare feet burn on the 140-degree F. surfaces.

What did you learn? Mounds are classified by shapes: crescentic, linear, parabolic. Particles of magnetite give the dunes a five-o'clock shadow; you can "shave" off the black specks with a magnet. The dunes look drier than a lecture on geomorphology, but they are actually one huge sponge. Dig down only a few inches and you'll hit wet sand.

Who did you meet? Matt Morscher of nearby Colorado Springs, who was strapped to a snowboard and carving soft-butter turns. "The sand is so fine it just takes off the layer of wax" on his board, he says. Jeff Aslan of Boulder, Colo., brought a makeshift toboggan. Despite spraying lube on the bottom, the sled went nowhere fast. Neither surfing device looked as cool as the tricked-out dune wheelchair available for handicapped visitors.

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