Devils Tower is an eroded laccolith in the Black Hills of Wyoming. A laccolith forms when molten magma forces its way into a rock formation, then cools and hardens. As the surrounding rock erodes away over time, the hardened former magma remains. The streaked surface of Devils Tower reflects the polygonal shaped fractures (columnar joints) that formed as magma contracted as it cooled and hardened. Devils Tower rises 1,267 feet above the nearby Belle Fourche River and according to the National Park Service, the summit is roughly the size of a football field. Photo credit: Alex Demas, USGS. Original public domain image from Flickr