Devil’s Tower, the first geological entity in the United States to be named a national landmark, is in Wyoming and is surrounded by Ponderosa pines. This rearing tower of rock, which has drawn people to it since Northern Plains tribes gathered there to worship, intrigues the thousands of people who come to see it each year. Of all the questions that these guests ask, one is most common and relatively difficult to explain. How is it that Devil’s Tower was ever formed in the first place?
Devil’s Tower is in an area that’s made up of sedimentary rock, which are rocks created by the dissolved particles of other rocks that have been moved by wind or water. Examples of this sort of rock are sandstone and shale. Devil’s Tower, on the other hand, is made up up igneous rock, which is made directly from molten rock coming to the surface. Devil’s Tower was a spire of molten rock that forced its way from deep inside the earth through the surface, or near to the surface. As time wore on, the sedimentary rock that surrounded the tower eroded, leaving Devil’s Tower exposed. Sedimentary rock is much softer than igneous rock, thus it erodes faster. Devil’s Tower was left standing tall when everything else had been blown or shifted away from it.
That Devil’s Tower is made of igneous rock and the surrounding area is all sedimentary rock is an accepted fact, but scientists still can’t agree on how Devil’s Tower came to be. In 1907, the popular theory was that Devil’s Tower is a laccolith, which is a large intrusion of igneous rock that pushes up through sedimentary layers without reaching the surface. Other theories are that Devil’s Tower is a volcanic plug, or the neck of an extinct volcano, though both of these theories aren’t as popular since they don’t fit the geologic norm of that part of Wyoming. However, regardless of the debate as to how it came to be, Devil’s Tower has existed for hundreds of years, and all signs point to it staying right where it is for hundreds of years more.