The Solitario is a structural dome developed in Paleozoic and Cretaceous rocks above an Eocene granite laccolith intrusion.

The dome is associated with radial rhyolite to trachyte dikes and sills and erupted ash flow tuffs.

[2] The Paleozoic rocks of the dome consist of a 2.6 km thick section of intensely-folded Cambrian through Early Pennsylvanian sediments.

The Paleozoic rocks were deformed and thrust into the area from the southeast during the Ouachita orogeny.

Erosion and downcutting following the Pleistocene deepening of the Rio Grande to the southwest and south have produced the current topographic expression of the area.