[Illustration: As millions of years went by, the soft sedimentary rocks were eroded, exposing what eventually became known as Devils Tower and the Little Missouri Buttes. The erosion process continued, baring more and more of the dense, gray rock. Apparently, as the magma cooled, the rock contracted and fractured into columns of 4, 5, 6, or more sides. The larger columns are 2.5 meters (8 feet) in diameter at their base and taper to about 1.2 meters (4 feet) at the top.] [Illustration: Today the Tower rises 264 meters (867 feet) from its base to an elevation of 1,560 meters (5,117 feet). The top is 386 meters (1,267 feet) above the Belle Fourche River at the entrance road. The tear-drop shaped top measures 91 meters (300 feet) from north to south and 55 meters (180 feet) from west to east. The sides rise almost vertically from the base for 12 to 30 meters (40 to 100 feet) to a narrow bench, from which they again rise steeply to the summit.] A _thwack_ of an ax against wood puts an end to my daydreaming. My companion the cottontail hops for cover. The pair of magpies that have been feeding on the remains of a road-killed ground squirrel flash upward to safety. The gradual awakening of campground life inspires woodpeckers to hammer in the cottonwoods, and a yellow-breasted chat adds its odd jibber to the collected noise. Gathering up knapsack and camera. I start my hike to the Tower. Already the sash of river fog has lifted and the air warmed to shirtsleeve comfort. From somewhere on the red cliffs that gown the Tower’s base, the faint singing of a rock wren beckons. Ahead lie 13 kilometers (8 miles) of trail, looping through a mosaic of sights, sounds, and smells of grassland, pine forest, woodland, and river. From Dog Town to Ant Colony Leaving the campground, I follow the trail that leads through the prairie dog town. The prairie dogs stand upright as I approach. The ones nearest the path begin their warning call, a monotonous “_churk-churk-churk-churk_.” The closer an intruder comes, the lower the animals sink into their holes, and the faster and shriller the chant becomes. Finally, with a last flick of its nervously twitching tail, each disappears into the safety of its burrow. Prairie dogs, like the bison that once shared their vast range, are now reduced to remnant populations. Two hundred years ago, there were billions of prairie dogs on the shortgrass plains; these large ground squirrels had successfully adapted themselves to the harsh conditions. Perfect digging machines, they escape most predators and the extremes of the weather by spending more than half their lives underground.