Landscape orientation of Devils Tower in Wyoming United States. Devils Tower with a blue sky and wispy clouds. Devils Tower rises above the surrounding grassland and ponderosa pine forests like a rocky sentinel. Geologists have studied the formation since the late 1800s, and today still wonder how it formed. Although much of the Tower’s geologic story is agreed upon, theories differ on certain details. Protected in 1906 for its scientific value, Devils Tower remains a place of scientific study and public wonderment. We know that the Tower is formed of a rare igneous rock, phonolite porphyry, and is the largest example of columnar jointing in the world