Final answer:
Devils Tower National Monument in Wyoming is a geological landmark composed of phonolite porphyry, an igneous rock that suggests it was formed by volcanic processes. The columns of Devils Tower are predominantly hexagonal, not octagonal.
Step-by-step explanation:
Devils Tower National Monument is a geological feature located in Wyoming. It is not a volcano plug but is often believed to be either a laccolith or the core of an ancient volcano that has since eroded away. Devils Tower is indeed located in Wyoming, making that statement true. The rock formation is primarily composed of phonolite porphyry, which is an igneous rock, indicating that the tower was formed by volcanic processes, although not in the form of a classic volcanic eruption like those at Hawaii Volcanoes National Park or Mount St. Helens National Volcanic Monument. Lastly, although Devils Tower exhibits impressive columnar jointing, its columns are not typically octagonal; they are mostly hexagonal.