The Phu Phan mountain range, geologically speaking, is part of the Khorat Group. This geological unit consists of Mesozoic sandstone, shale, and conglomerate formations. Its distinctive geomorphology is that of a "mesa," characterized by flat tops and steep cliffs. This landscape was sculpted by millions of years of uplift and erosion, leading to the formation of an inverted dome-shaped rock arch known as the "Phu Phan Dome," an important natural resource reservoir.