The Suguta Valley lies along the axis of the Gregory Rift, which has been faulting in this area since the Pliocene along a belt wide. The belt lies between the Ngiro basement uplift to the east and the Loriu Plateau to the west, and is thicker in the eastern part. Exposed volcanic rocks include basalts, tuffs and ash formed between 4.2 and 3.8 million years ago, the products of trachytic volcanism from 3,8 to 2.6 million years ago and basaltic and alkali basaltic rocks created from that period until the present.