The forces of erosion have shaped the park, but there is also a geologic structure that gives the park its wonderful arches and other rocks.

Underneath the park is a huge layer of salt, called the Paradox Formation. While we think of salt as a solid, under pressure it can slowly flow. This has let the rocks at the surface shift, producing many vertical fractures. These fractures set the stage for the formation of arches, columns, and other strange formations.