Kitsu Peak is formed mainly of Pliocenevolcanic rocks of the Spectrum Formation which consists of comendite, pantellerite and pantelleritic trachyte. These rocks are in the form of lava flows as well as minor breccia and ash flow deposits.[3] The Spectrum Formation is the eroded remains of a large lava dome that forms the current pyramidal peaks and ridges of the Spectrum Range. Truncated remnants of thick, gently dipping trachyte flows at the summit of Kitsu Peak indicate that the summit of the original dome was higher in elevation than it is today.[4]