Mt. Sunflower is the highest point in Kansas. It is capped by the final erosional detritus to flood over the Great Plains in the Late Miocene or Early Pliocene, the top of the Ogallala Group. The low relief on this surface gives an idea of the broad region of deposition existing perhaps as recently as 5 Ma. Fluvial conglomerates in this formation come from the Rockies a couple of hundred kilometers to the west.